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LIBRARIES

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This is to certify that the

dissertation entitled

Thermomorphogenesis

presented by

John Enos Erwin

has been accepted towards fulﬁllment .
of the requirements for

Ph . D. degree in Horticulture

K7 «//0& #444 a 5L

Major professor

Date March 22, 1991

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‘Thermomorphogenesis'

BY

John Enos Erwin

Thesis

Submitted To
Michigan State University
In Partial Fulfillment Of The

Requirements For The Degree or

DOCTOR OF PHILOSOPHY

Department Of Horticulture

1991

ABSTRACT

TH ERMOMORPHOG ENES I S

BY

John Enos Erwin

Plant stem elongation, leaf expansion, and leaf orientation
were influenced more by the difference (DIE) between day (DT)
temperature and night (NT) temperature (DT-NT) than absolute
temperature between 10 and 30°C in a wide range of plant
species. Stem elongation, leaf orientation, and leaf
expansion increased as DIF increased. Light quality (R/FR),
DIF, and application of GA“, or ancymidol interacted to affect
stem elongation. The percentage stimulation of internode
elongation by far red light and GA“, decreased as DIF
increased. In contrast, inhibition of stem elongation by
ancymidol increased as DIF increased. The ratio of
W male/female flower number increased as DIF
increased. The increase in male flowers relative to female
flowers and the interaction between light quality, DIF and
exogenous applications of GA,”7 and ancymidol suggested that
the transduction pathway for temperature effects on stem
elongation may involve endogenous gibberellin levels. A
system using angular displacement transducers was developed to
measure the kinetics of plant stem elongation. Stem

elongation rate varied during a 24 hr period. Maximum

ii

response to DIF occurred during the last 2 hours of the night
period and the first 2 hours of the day period. The basis for
the differential sensitivity of stem elongation to temperature
is discussed with respect to the effect of DIF on circadian

stem elongation rhythms.

iii

Dedication

This thesis is dedicated to my friends. Without them.
this thesis would not have been possible. Each of them is

special in their own way. I love them all very much.

Timothy R. Cefai
Royal D. Heins
Desmond R. Layne
Robert J. Lechnar
Brian J. Kovanda

Mark V. Yelanich

iv

Acknowledgments

The process of initiating and completing a doctorate
thesis can be grueling. Although it was difficult, I never
regretted undertaking the task. Receiving my doctorate is a
dream which has been dear to me for some time.

Upon finishing this dissertation the thought has occurred
to me that I have never learned quite so much in so short a
period of time. The experience has been invaluable to me.
Interestingly, the greatest benefit of the dissertation
process to me has not been the gaining of scientific knowledge
but rather personal growth. Fortunately, I had a major
professor, friends, and family who appreciated this process

and tolerated my ‘growing pains'.

Table Of Contents

Page
List Of Tables . . . . . . . . . . . . . . . . . . . viii
List Of Figures. . . . . . . . . . . . . . . . . . . xiii

Section I

Thermomorphoqenesis In W

Abstract . . . . . . .
Introduction . . . . .
Materials And Methods.
Results And Discussion
Literature Cited . . .

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Section II

Temperature Effects On Lily Development Rate
And Morphology From The Visible Bud Stage Until Anthesis

Abstract . . . . . . . . . . . . . . . . . . . . . . . 10
Introduction . . . . . . . . . . . . . . . . . . . . 11
Materials And Methods. . . . . . . . . . . . . . . . . 13
Results and Discussion . . . . . . . . . . . . . . . . 15
Literature Cited . . . . . . . . . . . . . . . . . . . 19
Section III
Temperature And Photoperiod Effects On
Fuchsia x hybrid; Morphological Development
Abstract . . . . . . . . . . . . . . . . . . . . . . . 29
Introduction . . . . . . . . . . . . . . . . . . . . . 30
Materials And Methods. . . . . . . . . . . . . . . . . 32
Results . . . . . . . . . . . . . . . . . . . . . . . 35
Discussion . . . . . . . . . . . . . . . . . . . . . . 38
Literature Cited . . . . . . . . . . . . . . . . . . . 44

vi

Section IV

Differential Sensitivity Of Plant Stem

Elongation To Temperature Fluctuations During The Day

Abstract . . . . . . .
Introduction . . . . .
Materials And Methods.
Results And Discussion
Literature Cited . . .

Section V

68
69
71
73
75

Interaction Between Light Quality, Growth Regulators
And The Relationship Between Day And Night Temperature

On Euchsig x hybrigg

Stem Elongation

Abstract . . . . . . . . . . . . . . . . . . . . . . 85
Introduction . . . . . . . . . . . . . . . . . . . . 86
Materials And Methods. . . . . . . . . . . . . . . . 88
Results And Discussion . . . . . . . . . . . . . . . 90
Literature Cited . . . . . . . . . . . . . . . . . . 95
Section VI
A System To Measure
Plant Stem Elongation Kinetics
Abstract I O O O O O O O O O O O O O O O O O O O O O O 1 19
Introduction . . . . . . . . . . . . . . . . . . . .120
System Composition . . . . . . . . . . . . . . . . . .122
Discussion . . . . . . . . . . . . . . . . . . . . .124
Literature Cited . . . . . . . . . . . . . . . . . .130
Section VII
Appendices
A . Temperature Effects W ‘Madisto '
Flower Initiation . . . . . . . . . . . . . . .142
B. Thermomorphogenic .And Photoperiodic Responses Of
' ‘Dallas Jewel' . . . . . . .147
C. Temperature Effects On Sex Expression In ggguggigggggg
O O O O O O O O O O O I O O 0 O O 0 O O O O O O O 153
D. Temperature And Photoperiod Effects On Chlorophyll
Content Of Eggg§1g_x;nygrig§. . . . . . . . . . .155
E. Temperature Effects On Miscellaneous Species. . .164

vii

List Of Tables

Table 2m
Section I
Thermomorphogenesis In W
1 Influence of day and night temperature on Lilium
mm cv ‘Nellie White' plant height,
internode length, and leaf orientation . . . . 4
2 Influence of day and night temperature on Mtg

lgggiﬁlg;g_ cv ‘Nellie White' leaf and flower
length 0 O O O O O O O O O O O O O O O O C O O 5

3 The effect of ancymidol and the day/night
temperature regime on Lilyzm ”l oggiflomm Thumb.
plant height at anthesis. . . . . . 6

Section II

Temperature Effects On Lily Development Rate
And Morphology From The Visible Bud Stage Until Anthesis

1 The influence of day and night temperature on the
number of days from visible bud to open flower on
Lgiigm_lgggiglgggm cv. Nellie White. . . . . . 22

Section III

Temperature And Photoperiod Effects On
Eggb§i§_z;bypzig§ Morphological Development

1 Setpoints and actual average day and night
temperatures (DT/NT) for all environmental
treatments for 1988 and 1989. . . . . . . . . 49

2 The effect of day temperature, night temperature and
photoperiod on £Q£h§1§_x;byggig§ ‘Dollar Princess‘
internode length at anthesis. Long days were
delivered as a 9 hour photoperiod plus a 4 hour
night interruption using incandescent lamps. Short
days were delivered as a 9 hour photoperiod only.

0 I O I O O O O O O O O O O O O O O O O O O O 50

viii

Ighlg £992

Regression coefficients calculated to predict
internode length of W ‘Dollar
Princess' plants from experiments conducted during
1988 and 1989 studying the effect of day
temperature, night temperature, and photoperiod on

plant morphology. Comparison of slopes and
intercepts were evaluated using the technique
outlined by Snedicor and Cochran (1967). . . 52

The effect of day temperature, night temperature and
photoperiod on £g_ﬂs1;_x_by§;1gg ‘Dollar Princess'
single leaf area at anthesis. Long days were
delivered as a 9 hour photoperiod plus a 4 hour
night interruption idelivered using incandescent
lamps. Short, days were delivered as a 9 hour
photoperiod only. Leaf area was calculated by
measuring leaf length and.width and calculating the
area of an ellipse, i.e. leaf area = (width/2) *
(length/2) * 3.78. . . . . . . . . . . . . . 53

Regression coefficients calculated to predict single
leaf area of Eychs1g 1 hybrid; ‘Dollar Princess'
plants from experiments conducted during 1988 and
1989 studying the effect of day temperature, night
temperature, and.photoperiod.on,Eucb51a morphology.
Comparison of slopes and intercepts were evaluated
using the technique outlined by Snedicor and
Cochran (1967). . . . . . . . . . . . .. . . . 55

The effect of day temperature, night temperature and
photoperiod on zy_g§1g_1__xg;1gg ‘Dollar Princess'
branch number at anthesis. Long days were
delivered as a 9 hour photoperiod plus a 4 hour
night interruption.ldelivered using incandescent

lamps. Short days were delivered as a 9 hour

photoperiod only. A branch was defined as any

axillary break which has 2 or more nodes. . . 56
Section IV

Differential Sensitivity Of Plant Stem
Elongation To Temperature Fluctuations During The Day

The effect of warm and cool temperature fluctuations
at different times of the day on L111gm_1gngiﬁlg;gm
CV“ ‘Nellie 'White' internode length (cm). .All
plants were grown at 20°C. Plants were moved to
either 25°C or 15°C at the prescribed times. The
photoperiod was initiated at 0900 and was
terminated at 1700 hr.. . . . . . . . . . . . 77

ix

Table Bags

The effect of warm and cool temperature fluctuations
at different times of the day on L111gm_122g1£1222m
cv ‘Nellie White' internode length (cm). All
plants were grown at 20°C. Plants were moved to
either 25°C or 15°C at the prescribed times. The
photoperiod was initiated at 0900 and was
terminated at 1700 hr.. . . . . . . . . . . . . 78

Section V.

Interaction Between Light Quality, Growth Regulators
And The Relationship Between Day And Night Temperature

On Eggh g1; 1 hy2r1d§ Stem Elongation

Experimental treatments designed to study the
interaction between light quality and day/night
temperature environments on c da cv
Dollar Princess internode elongation. Plants were
moved among chambers to deliver the temperature
treatments and between lighting sources during the
night period to complete the treatment
combinations. Lighting treatments consisted of
supplemental lighting from red (R) or far red (FR)
light sources for 30 minutes at the beginning of
the night (EOD), continuous lighting (CONT), or
darkness (DARK) during the scotoperiod. GA“? was
applied as five 20 ul droplets of a 10 ppm
concentration solution to the uppermost leaf pair 5
days after the initiation of the experiment using a
digital Finnipippette (Cole-Palmer). .Ancymidol was
applied as five 20 ul droplets of a 50 ppm
concentration solution to the uppermost leaf pair 5
days after the initiation of the experiment. . .101

The effect of temperature, light quality, and growth

regulators on £ucﬁg1g 1: bybg1gg cv ‘Dollar
Princess' internode length. Temperature

environments were 24 day temperature/16 night
temperature (+ DIF), 20 day temperature/20 night
temperature (0 DIF) , and 16 day temperature/24
night temperature (- DIF) . Lighting treatments
were either end-of—day (EOD), continuous (CONT), or
darkness (DARK). Light sources were either red (R)
or far red (FR). Growth regulator applications of
five 20 ul droplets of either a 10 ppm solution of
GA 7 (GA) or alpha-cyclopropyl-alpha-(4-
methoxyphenyl) -5-pyrimidiemethanol (anc) ‘were
applied 5 days after the initiation of temperature
and lighting treatments. . . . . . . . . . . . .103

X

Appendix A

Temperature Effects

£gb1um2g;ggzg_§zuggg§g ‘Madisto' Flower Initiation

The effect of day and night temperature on total
break number per pot of Sghlumhergera_£ruh2_ta cv

‘Madisto'. . . . . . . . . 146

The effect of day and night temperature on

phyl loc lade number per pot of

gzgngggg cv ‘Madisto' . . . . . . . . . . . . 146
Appendix B

Thermomorphogenic And Photoperiodic

Responses Of ﬂepﬁrg1e21§_ex§1;§§a ‘Dallas Jewel'

ﬂeehrgleei§_erelrara ‘Dallas Jewel' frond length.

leaflet number per frond and leaf area. Daylength
was 9 hours. The long day treatment consisted of
night interruption lighting from 2200 to 0200 hr
delivered with incandescent lamps at an intensity
of 2 umol 5’1 mi. Frond length and leaflet number
data were collected on a representative frond on
. each plant. . . . . . . . . . . . . . . . . . . 151

The effect of day temperature, night temperature and

photoperiod on Nephzg1§p1s.gya1ta§a ‘Dallas Jewel'

stolon number. . . . . . . . . 152

Appendix C

Temperature Effects Sex Expression In Qggyzg1£gg§§§

Effect of temperature and light fluctuations on
Qgcurb1§acgge cv Tay-Belle sex expression. Plants
were grown for 60 days. Temperature and/or
photoperiod length were 12 hr. Light intensity was
150 umol s'1 m'z. In the ‘constant light-fluctuating
temperature' treatment, temperatures fluctuated
between 23 and 17 C. Temperature was constant 20 C
in 'the ‘constant. temperature-fluctuating light'
treatment. . . . . . . . . . . . . . . . . . . 154

xi

Appendix D

Temperature And Photoperiod
Effects On Plant Chlorophyll Content

The effect of day and night temperature on
chlorophyll a, chlorophyll b and p chlorophyll
content of 53921511 x nybz1'ga cv Dollar Princess

grown under a 9 hr photoperiod. . . . . . . . . 156

The effect of day and night temperature on
chlorophyll a, chlorophyll b and p chlorophyll
content of W cv Dollar Princess

grown under a 12 hr photoperiod . . . . . . . . 158

The effect of, day and night temperature on
chlorophyll a, chlorophyll b and p chlorophyll
content of dra ema andi 1 a cv Bright
Golden Anne grown under a 9 hr photoperiod. . . 160

The effect of day and night temperature on
chlorophyll a, chlorophyll b and p chlorophyll

content of £_1g;ggg1_m_ﬁg;§gggm cv Red Elite grown
under a 9 hr photoperiod. . . . . . . . . . . . 162

Appendix E

The Effect Of Day And Night Temperature And

Photoperiod On Stem Elongation Of Miscellaneous Species

1

The effect of day temperature, night temperature,
and photoperiod on Kagth1gm §§111ma213m internode
length (cm). Photoperiod was 9 hr long (short day)
or 9 hr plus a 4 hr night interruption with light
from incandescent lamps (long day). . . . . . . 165

The effect of day temperature, night temperature,
and photoperiod.on gggym1§_ggt1yym internode length
(cm). Photoperiod was 9 hr long (short day) or 9
hr plus a 4 hr night interruption with light from
incandescent lamps (long day). . . . . . . . . .166

The effect of day temperature, night temperature,

and photoperiod on ﬁtreptogarpus £02111§ internode
length (cm). Photoperiod.was 9 hr long (short day)

or 9 hr plus a 4 hr night interruption with light
from incandescent lamps (long day). . . . . . . 167

xii

List Of Figures

Section I

Thermomorphogenesis In W

Response surface plots generated from predicted
final plant height (a), internode length (b), and
leaf orientation (c) on W Thumb. cv
‘Nellie White' as influenced by day and night
temperature. Surfaces were based on the regression
functions: (a) 1.47602*DIF + -0.0416*DT*NT

+1.91394*AVG TEMP +25.66l (r7- = 0.84), (b)
0.0223117*DIF + -0.000752*DT*NT + O. 0390916*AVG TEMP
- 0.0652671 (r2 = 0.82), (c) 1.80309*DIF + -
0.07495*DT*NT + 4.02815*AVG TEMP - 55.18 (r2 =
0.68), respectively. . . . . . . . . . . . . . . 3
Appearance of L111um long1110rum Thumb. cv ‘Nellie
White' at anthesis ‘when. grown under four

temperature regimes with day temperatures (DT) 4 C
cooler than night temperatures (NT). Plants grown
at higher average temperatures flowered earlier
than plants grown at cooler average temperatures.
As plants grown at higher temperatures reached
anthesis, they were placed in a cooler (4 C) until
plants grown at cooler temperatures reached
anthesis. Stem elongation did not occur in the
cooler. When all plants had reached anthesis, the
photograph was taken . . . . . . . . . . . . . . 5

Relationship between L111gm long1f1oggm Thumb. cv.
‘Nellie White' plant height at anthesis and the

difference (DIF) between the day temperature (DT)
and the night temperature (NT). Squares represent
mean plant heights for each temperature treatment.
The solid line represents the regression function
1.4860*DIF - 0.0416*DT*NT + 1.9139*ABG TEMP +
25.661 (r2 = 0.84). The regression line also
represents the effect of both the DT by NT
interaction and the effect of average temperature
on final plant height. temperature . . . . . . . 5

xiii

Rage

Response surface generated from predicted final leaf
length of ' 10 if m cv. ‘Nellie White' as
influenced by day and night temperature. Predicted
leaf length was based on the regression function
0.581132*DT + -0.012254*DT2-+ -O.425519*NT + 19.49
(r2=0.72)...................6

Section II

Temperature Effects On Lily Development Rate

And Morphology From The Visible Bud Stage Until Anthesis

1

Relationship between L111hh_1ghg1£1gghh cv

‘Nellie White' height increase during phase III and
the idifference between the day and night
temperature (OT-NT). Squares represent mean plant
heights for each temperature treatment as
determined from 5 plants. The solid line
represents the function Height Increase During
Stage III = (0.496946*DIF) + (.150561*DIF2) + 18.01
(r2=.77)...................24

Liligm_12hg1112rhh ‘Nellie White' bud development

rate per hour as a function of temperature. Twp
models are presented. A linear model based on
average daily temperature (ADT) is presented (- - -
) between 14 and 22 C based on the function Daily
rate = -0.740904E-02 + (0.2090363-02 * ADT). A
nonlinear model is presented ( ----- ) based on the
function Daily rate = b1-tl% * ((HDT * DT) + (HNT
* NT))/24 + b3/10 * nor * M" + b4/14 * HNT * NT3 (r2
= .96). 8,, b, b3, and b, are parameter
coefficients. HIST and HNT are hours of day and
night, respectively. . . . . . . . . . . . . . 26

Section III

Temperature And Photoperiod Effects On

£uchs1a y hybh1da Morphological Development

The effect of the difference between day and night
temperature (day temperature - night temperature )
on Egchgig z; hybrida ‘Dollar Princess' internode
length on plants grown during the 1989 experiment.
Plants were grown under long day conditions, i.e. a
9 hr photoperiod plus a 4 hr night interruption
using incandescent lighting. . . . . . . . . . 59

xiv

Base

The effect of the difference between day and night
temperature and on Eu ugh§1g 1 hyhz1da ‘Dollar
Princess' internode length on plants grown
under long days (9 hr photoperiod plus 4 hour
night interruption using incandescent lamps) and
short days (9 hr photoperiod). Data were
normalized across 1988 and 1989 experiments within
photoperiod treatments. . . . . . . . . . . . . 61

The effect of the difference between day and night
temperature and photoperiod on W
‘Dollar Princess' leaf area on plants grown under
long days (9 hr photoperiod plus 4 hour night
interruption using incandescent lamps) and short
days (9 hr photoperiod) . Data were normalized
across time within each photoperiod. . . . . . 63

The effect of average daily temperature and
photoperiod on the number of branches at anthesis
on plants grown under long days (9 hr photoperiod
plus 4 hour night interruption using incandescent
lamps) or after 78 days on plants grown under short
days (9 hr photoperiod). Only data from the 1988
experiment is presented. . . . . . . . . . . . 65

Section IV

Differential Sensitivity Of Plant Stem

Elongation To Temperature Fluctuations During The Day

The effect of the time and duration of a warm or
cool temperature exposure on L111hm_12hg1119;ym cv
‘Nellie White' internode length. Plants were grown
at constant 20°C accept when plants received the
cool temperature pulse (15°C) . The photoperiod was
initiated at 0900 and was terminated at 1700 hr.
Significance between treatment.means was determined
using Tukey's test for mean separation (H.S.D.).

O O O O O O O O O O O O O O O O O O O O O O O O 80

The effect of the time and duration of a warm
temperature exposure on £51y1h__§21§hggh§ and
Impg_1gh§_yg11§;1hhg internode length. Plants were
grown at constant 20°C accept when plants received
the warm temperature pulse (25°C) . The photoperiod
was initiated at 0900 and was terminated at 1700 hr.
Linear regression analysis employed an alpha value
of 0.05. . . . . . . . . . . . . . . . . . . . 82

XV

figure

P192

Section V.

Interaction Between Light Quality, Growth Regulators

And The Relationship Between Day And Night Temperature

1a

1b

0n Engagia_x_h22rida stem Elongation

Light spectra of daylight versus artificial lighting
composed of high pressure sodium and incandescent
lamps used in this experiment. . . . . . . . . 106

Light spectra of red and far red light sources used
to deliver supplemental lighting during the
scotoperiod. . . . . . . . . . . . . . . . . . 108

Percent stimulation of elongation of the second
internode of Egghsia 1 hybg1dg cv Dollar Princess
when grown under different day/night temperature
environments and light quality treatments. Light
quality treatments were applied during the

scotoperiod . Data is presented as the percent
stimulation as compared to plants which received no
lighting treatments. . . . . . . . . . . . . . 110

Percent stimulation of elongation of the second
internode of £gghs1a 1 hyhridg cv Dollar Princess
following an application of GA 7 when grown under
different red lighting treatments. Red lighting
treatments were applied during the scotoperiod.
Data is presented as the percent stimulation
compared to plants which received the red lighting
treatments or darkness only. . . . . . . . . . 112

Percent inhibition of elongation of the second
internode of £gchs1g x hybg1ga cv Dollar Princess
following an application of ancymidol when grown
under different far red lighting treatments. Far
red lighting treatments were applied during the
scotoperiod. Data is presented as the percent
inhibition compared to plants which received the
far red lighting treatments or darkness only. 114

Comparison of the increase in second internode
length resulting from red lighting only,
application of GA," only , or red lighting plus

application of GA“; on £2£b§1Q1&_ﬂE2£iéé cv Dollar

Princess. 0 C O O O O 116

xvi

Section VI.

A System To Measure
Plant Stem Elongation Kinetics

A schematic representation of the circuit block
diagram of an angular displacement transducer.

0 O O O O O O O O O O I O O O O O O O O O O O O 134

Schematic diagram of a system developed to
continuously measure plant stem elongation. Only
one transducers is shown, however, a total of 8
transducers were employed in 2 growth chambers. All
transducers were controlled by a single
microcomputer. . . . . . . . . . . . . . . . . 136

The output function of an angular displacement
transducer. Note the typical linear range. . . 138

The effect of increasing pulley diameter on the
usable distance for direct linear measurement and
the minimum mass required to turn the transducer
shaft. The usable distance was calculated by
dividing the circumference of the selected diameter
pulley by 6 to yield the linear 60° distance. The
maximum torque required to start rotation of the
shaft is 5 g-cm. If this is held constant the
minimum counterweight mass could be calculated from
the equation: Torque (N-m) * Moment (m) = Mass (N)
(Sears et al., 1982). . . . . . . . . . . . . . 140

Appendix A

Temperature Effects

ﬁgnlgmgggg§;g_;;gng§;§ ‘Madisto' Flower Initiation

The effect of average daily temperature on the time
from flower induction to anthesis on ﬁgblgmggzggzg

gggnggtg ‘Madisto'. . . . . . . . . . . . . . . 144

The effect of night temperature on the ratio of
flowers to flowers plus phylloclades on

W ‘Madisto'. - . - . - - - 144

xvii

ﬁgure Page

Appendix B
Thermomorphogenic And Photoperiodic
Responses Of Hepbz91g21§_§xglgg£g ‘Dallas Jewel'
1 The effect of average daily temperature and
photoperiod on frond unfolding rate of ﬂgpngglgpis
gxglgggg ‘Dallas Jewel'. . . . . . . . . . . . 150

xviii

Section I

Thermomorphogenesis

In Li11um Loggiflorgm Thunb.

Amer. J. Bot. 76(1): 47-52. 1989.

THERMOMORPHOGENESIS IN LILIUM LONGIFLORUM'

JOHN E. anm, ROYAL D. Hams, AND MERIAM G. KARLSSON
Department of Horticulture. Michigan State University. East lansing. Michigan 48824-1325

ABSTRACT

Stem elongation and leaf orientation in Lilium longtﬂorum Thunb. were inﬂuenced more by
the difference (01F) between day temperature (DT) and night temperature (NT) than absolute
DT or NT from 14 to 30 C. Plant height and internode length increased 129 and 382%,
respectively. as DlF (DT-NT) increased from - 16 to 16 C as compared to only 15 and 58%
when either DT or NT was increased from 14 to 30 C. respectively. Leaf orientation, defined
as the angle between a line perpendicular to the stem and the line from the leaf base to the leaf
tip. increased 43' (leaves became more upright) as DlF increased from - 16 to 16 C. in contrast
to plant height. internode length. and leaf orientation. leaf and ﬂower length were inﬂuenced
more by absolute temperature than 011’. Leaf and ﬂower length decreased 32 and 14%, re-
spectively. as NT increased from 14 to 30 C. DT had little eﬂ'ect on either leaf or ﬂower length.
The inﬂuence of DlF on stem elongation suggested that thermomorphogenesis was not a function
of tatal plant carbohydrate or carbohydrate translocation. lnstead. DlF appeared to inﬂuence
the endogenous gibberellin content or the response of plant tissue to gibberellin. Similarities
between thermomorphogenic plant responses and photomorphogenic plant responses suggested

that these two processes may be related with respect to their perception andor transduction.

GROWTH is thermopcriodic in many plant
species (Dorland and Went. 1947; Went, 1953;
Viglierchio and Went, 1957; Hellmers and
Sundahl. 1959; Groves and Lang. 1970; Erwin
and Heins. 1985; Karlsson and Heins, 1986).
For instance. plant height is greater when plants
are grown with day temperatures (DT) warmer
than night temperatures (NT) in a wide range
of plant species including L,t-'copersicon (Went,
1944; 1945), Phaseolus (Viglierchio and Went,
1957), Chrysanthemum (Karlsson and Heins.
1986), and Capsicum (Dorland and Went,
1947). Other plant characteristics which re-
spond to diurnal changes in temperature are
ﬂower size (Karlsson and Heins, 1986), leaf
shape (Fischer, 1954; Njoku, 1957), and leaf
orientation (Erwin and Heins, 1985).

Plant height in L. longiﬂorum Thunb. cv.
Ace was inﬂuenced by DT and NT (Wilkins,
1973). Lily plants grown with a 32 C OT and
16 C NT from the visible bud stage to anthesis
were 149% taller than plants grown with a 16
C OT and 32 C NT (Wilkins, 1973). The cv.
Nellie White responded similarly to temper-
ature, with respect to plant height as cv. Ace
(Erwin and Heins, 198 5). In addition, leaf size,
ﬂower size, and leaf orientation were also in-

' Received for publication 28 June 1987: revision ac-
cepted 5 May 1988.

The authors appreciate the assistance of Cathey Fre-
denburg. Robert Berghage. James Eppinlt. and Sharon
Stmad during this project. Lily bulbs were donated by the
Paciﬁc Bulb Grower's Association. This project was fund-
ed in part by a grant from the Fred C. Gloecltner Foun-
dation.

47

ﬂuenced by DT and NT with cv. Nellie White
(Erwin and Heins. 1985). In contrast, plant
height of Lilium Iongiﬂorum Thunb. cv. Croft
was not greatly inﬂuenced by DT or NT be-
tween 10 and 27 C (Smith and Langhans, 1961).

Morphological responses to temperature will
be referred to as thermomorphogenic in this
paper. The term is derived from the Greek
derivatives Ihermc. meaning heat; morphos.
the quality of having form; and gignesthai. to
be born. Hence, thermomorphogenesis. the ef-
fect of temperature on plant morphogenesis.
The term thermomorphogenesis is consistent
with the term photomorphogenesis which de-
scribes the eﬂ‘ect of light on plant morphogen-
em.

The objective of this study was to quantify
thermomorphogenic responses in Lilium Ion-
gtﬂorum. In the process of determining mor-
phogenic responses to temperature, we wished
to gain some insight into what processes may
control thermomorphogenic responses.

MATERIALS AND sermons-Lilian: longiﬂo-
rum Thunb. cv. Nellie White bulbs 17.7-20.3
cm in circumference were planted in 15.2 cm
plastic pots on 28 October 1985 in soilless
medium consisting of equal parts of Sphagnum
peat, perlite, and vermiculite (1:1:1). Potted
bulbs were placed in a controlled environment
greenhouse for two weeks where air tempera-
ture was adjusted to maintain a medium tem-
perature of 17 C 1- 1 C to encourage root de-
velopment. Plants were then vernalized in the
dark for 6 wk at 5 C. Following vernalization.

48

Plant Height (cm)

lnternode Length (cm)

Lee! Orientation (degrees)

0. 7

0.3 0.5

00.!
0444111111-..

AMERICAN JOURNAL OF BOTANY

 

 

 

 

 

IIIIIIIIIIIIIIII
'IIIIIIIIII

 

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ht].

 

 

 

 

 

 

 

 

 

 

 

 

 

llllll IIIIII
2,2.
1.6
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[Vol. 76

all plants were placed in a greenhouse under
natural photoperiodic conditions with con-
stant 20 C DT and NT. Upon shoot emergence.
plants received a long day treatment for 7 days
consisting of night interruption lighting from
2200 to 0200 hr delivered with incandescent
lamps at 2 micromol sec" rn'2 (400-700 nm
wavelength). After the long day treatment,
plants were returned to natural photoperiodic
conditions (ca. 9 hr, 15 min light span).

Time of ﬂower initiation was established by
terminal shoot dissections on randomly se-
lected plant samples starting 13 January 1986.
Plant samples were taken every 3 days. Flower
initiation was deﬁned as the ﬁrst visible sign
of a reproductive meristem (De Hertogh, 1976,
ﬁgure 2c). Flower initiation was observed on
100% of the sample on 22 January. One
hundred twenty-ﬁve plants were then selected
for uniformity based on plant height and leaf
number and moved to greenhouses with tem-
perature setpoints of 14. 18. 22, 26. or 30 C.
Actual average temperatures during the ex-
periment did nOt vary by more than 1.8 C from
the desired temperature setpoints. Plants were
moved among greenhouse sections at 0800 and
1800 hr each day to yield a total of 25 DT/
NT treatment combinations. Movement of
plants required approximately 30 min. An
Opaque curtain was pulled over the plants after
the plants were moved at 1800 and was re-
tracted just prior to 0800 to provide a l4-hr
scotoperiod to parallel the night temperature
treatment. Plants were spaced to provide 900
cm2 per plant.

During 1987, a group of Lilium Iongtﬂorum
Thunb. cv. Nellie White plants were grown as
speciﬁed above. At ﬂower initiation. 6 groups
of 10 plants each were placed in controlled
environment greenhouses maintained at 15.
20. and 25 C. Each group of plants was rotated
among greenhouses to yield a total of 9 DT/
NT temperature treatments. Within each tem-'
perature treatment the plants were divided into
2 groups of 5 plants each. One group was grown
as a control. The other group received two
applications of 0.25 mg ancymidol (alpha-cy-
clopropyl-alpha-(4-methoxyphenyl)—5-pyrim-

 

—

Fig. 1. Response surface plots generated from pre-
dicted ﬁnal plant height (a). internode length (b). and leaf
orientation (c) on Lilium longiﬂorum Thunb. cv. Nellie
White as inﬂuenced by day and night temperature. Surfaces
were based on the regression functions: (a) 1.48602-DIF
+ -0.0416-DT-NT + 1.91394-AVG TEMP + 25.661
1': " 084). (b10.0223117-DlF 4- - 0.000752cDT-NT
e 0.0390916-AVG TEMP - 0.0652671 (rz - 0.82). and
(c) 1.80309-DlF 4- -0.07495oDT-NT .. 4.02815-AVG
TEMP - 55.18 0" - 0.68). respectively.

January 1989]

idinemethanol) 7 and 14 days after ﬂower ini-
tiation to the plant apex. Ancymidol was
applied using a Labsystems Finnpipette Dis-
penser (20-200 111) as ten 100 pl droplets.

Data were collected at anthesis (terminal
ﬂower) on total plant height, leaf number.
aborted and non aborted ﬂower number, ﬂower
length, leaf length, and leaf orientation. Plant
height was deﬁned as the height of the plant
from the soil line to the tip of the uppermost
pedicel. Intemode length was calculated by di-
viding stern length by leaf number. Leaf num-
ber was constant, since plants had initiated
ﬂowers prior to placement in the experimental
environments. Leaf orientation was deﬁned as
the angle between a line perpendicular to the
stem and a line from the leaf base to the leaf
tip. A 0° leaf orientation indicated a horizontal
leaf orientation. Similarly, a positive angle of
leaf orientation indicated hyponastic, or up-
ward leaf orientation. and a negative angle of
leaf orientation indicated an epinastic. or
downward leaf orientation.

Data were statistically analyzed as a 5 x 5
factorial design with DT and NT as the main
factors for the 1986 data. Data were statisti-
cally analyzed as a split plot design with DT
and NT as the main factors and ancymidol
concentration as the subplots in the 1987 data.
The ANOVA subroutine of the “Statistical
Package of the Social Sciences“ (Nie. 1975)
was used for analysis of variance. The “All
Possible Subsets Regression (P9R)" and the
“Stepwise Regression (P2R)" subroutines of
the “Biomedical Statistical Software Package“
( Dixon. 1983) were used for multilinear regres-
sion analysis.

RESULTS AND mscussron—DT and NT in-
ﬂuenced plant height in opposite ways. Plant
height increased 64% as DT increased from 14
to 30 C with NT held at 14 C. Plant height
decreased 29% as NT increased from 14 to 30
C with DT held at 14 C. (Fig. la; Table 1).

DT and NT also interacted to inﬂuence plant
height. The inﬂuence ofNT on ﬁnal plant height
increased as DT increased. Increasing NT from
14 to 30 C decreased plant height 12.5 cm
(29%) when the DT was 14 C and 21.1 cm
(30%) when the DT was 30 C. In contrast, the
inﬂuence ofDT on ﬁnal plant height decreased
as NT increased. Increasing DT from 14 C to
30 C increased plant height 27.8 cm (64%)
when the NT was 14 C and 19.2 cm (61%)
when the NT was 30 C. The percent increase
in plant height due to increasing DT was not
inﬂuenced by NT and vice versa.

The relationship between DT and NT inﬂu-
enced ﬁnal plant height to a greater extent than

4
ERWIN ET AL—THERMOMORPHOGENESIS IN LILIUM 49

TA»! 1. Inﬂuence of day and night temperature on Lil-
ium longiﬂorum cv. Nellie White plant height. inter-
node length. and leaf orientation

 

 

 

Night
temp:- Day temperature (0
(C) 14 it 22 26 30
Plant height (cm)
14 43.8 54.6 62.2 68.4 71.6‘
18 40.5 45.8 57.0 60.8 63.5
22 31.8 42.4 44.4 50.8 50.8
26 30.2 39.0 41.2 43.6 51.2
30 31.3 33.8 41.0 42.2 50.5
lnternode length (cm)
14 0.31 0.48 0.60 0.68 0.82
18 0.25 0. 38 0.56 0.64 -
22 0.23 0.31 0.46 0.48 0.54
26 0.22 0.27 0.41 0.45 0.46
30 ' 0.17 0.20 0.36 0.38 0.49
Leaf orientation (degrees)'
14 -5.9 - 5.0 11.6 18.9 26.3
18 -10.0 -17.9 5.8 11.9 14.7
22 -24.2 -10.2 -<» v 2.7 6.1
26 - 20.7 - 13.3 - 1.4 - 2.6 8.3
30 -16.7 -13.7 ~12.5 -7.3 1.7

 

. Values represent the experimental means. The greatest
SD was 7.2 cm. 0.1 cm. and 15.2 degrees for plant height.
internode length. and leaf orientation. respectively.

‘ Angle of the leaf. in degrees. between a line perpen-
dicular to the stem and a line connecting the leaf tip to
the leaf base.

DT. NT. or average temperature. Plants grown
with a NT warmer than DT were consistently
shorter than plants grown with equal DT and
NT while plants grown with the NT cooler than
the DT were taller (Table 1). Plant heights were
similar when the relationship between DT and
NT was the same (Table 1). For example, the
plants shown in Fig. 2 were all grown with a
NT 4 C warmer than the DT. All the plants
had similar plant heights at anthesis (40.5, 42.4.
41.2, and 42.2 cm, respectively) despite the
very different average temperatures associated
with each temperature treatment. Similar ﬁnal
heights occurred on other plants with similar
relationships between DT and NT. Plant height
increased as DT increased relative to NT. Plants
grown with a 14 C DT/30 C NT were 40.3 cm
shorter than plants grown with a 30 C DT/l4
C NT temperature regime. The importance of
the relationship between DT and NT on plant
height is consistent with results of Lecharny,
Schwall. and Wagner ( l 985) who suggested that
the difference in temperature between the day
and night was critical in determining the rate
of stem elongation and/or phase resetting of
the stem elongation circadian rhythm in Che-
nopodium rubrttm.

The relationship between DT and NT was

5
50

Till tuttutnct or DAV
tturuAtuIt Ann '16!"
run-Atoll 0
W10!

Hutu!
rumour
Ar fLOlLI

 

Fig. 2. Appearance of Lilium longi/lorum Thunb. cv.
Nellie White at anthesis when grown under four temper-
ature regimes with day temperatures (DT) 4 C cooler
than night temperatures (NT). Plants grown at higher av-
erage temperatures ﬂowered earlier than plants grown at
cooler average temperatures. As plants grown at higher
temperatures reached anthesis. they were placed in a cooler
(4 C) until plants grown at cooler temperatures reached
anthesis. Stem elongation did not occur in the cooler. When
all plants had reached anthesis. the photograph was taken.

described in regression analysis as the diﬂer-
ence in temperature between DT and NT. i.e.,
DT minus NT (DIF). The DIF term was useful
in that it described the difference between DT
and NT and can‘ied a sign to indicate whether
DT or NT was greater. The importance ofDlF
in determining plant height was shown when
it was evaluated independently as a linear func-
tion of plant height; DlF accounted for 78%
of the variability in plant height among treat-
ment plants.

TABLE 2. Inﬂuence of day and night temperature on Lil-
ium Iongiﬂorum cv. Nellie White leaf and ﬂower length

 

 

 

Night
temper- Day temperature (C)
MUM
(C) 14 ll :2 26 to
leaf length (cm?
14 18.2' 21.0 20.8 20.2 19.6
18 17.0 18.0 19.5 18.4 19.1
22 16.6 16.7 16.7 17.8 16.8
26 15.6 14.7 15.7 15.3 15.0
30 12.4 13.3 13.8 14.0 13.6
Flower length (cmr
14 17.7 17.8 17.9 18.4 16.5
18 17.5 18.6 17.7 17.2 17.2
22 17.6 17.4 17.7 16.9 16.5
26 16.5 16.8 16.7 16.7 16.4
30 15.3 15.8 16.8 16.3 16.0

 

‘ Length from the point ofattachment of the leaf to the
leaftt

h Values represent the experimental means. The greatest
SD was 1.1 cm for both leaf and ﬂower length.

‘ Length from the point ofattachment ofthe petal to the
pedicel to the petal tip.

AMERICAN JOURNAL OF BOTANY

 

 

 

 

 

[VOL 76

30

A 0 Treatment Means

E — Regression Function

V 70‘

m

’8

5 60-

c

<

o4 50‘

<

33 40-

v

I

‘5 304

_°

0.
20 1 . v . . v f
-20 —-15 —10 -5 0 5 10 15 20

Difference Between DT And NT ('C)

ﬁg 3. " ' ' " ‘ l ' ‘ Thunb.
cv. Nellie White plant height at anthesis and the difference
(DIF) between the day temperature (DT) and night tem-
perature (NT). Squares represent mean plant heights for
each temperature treatment. The solid line represents the
regression function 1.48600D1F - 0.0416-DT0NT +
1.9139-AVG TEMP 0 25.661 (r-‘ - 0.84). The regression
line also represents the eﬂ'cct of both the day temperature
by night temperature interaction and the effect ofaverage
temperature on ﬁnal plant height.

lntemode length responded to OT and NT
in a similar fashion as plant height (Fig. lb;
Table 1). As DlF increased from - 16 to 16 C
internode length increased 382% (0.65 cm). No
difference in internode length was observed
between intemodes which matured early in
plant development as opposed to late in plant
development.

As with plant height and internode length,
the relationship between DT and NT inﬂu-
enced leaf orientation of Lilium Iongiﬂorum
(Table l) to a greater extent than absolute DT
and NT. An increase in DIF from - 16 to 16
C increased leaf orientation 43°.

Leaf and ﬂower length were inﬂuenced more
by absolute DT and NT than DIF. Leaf length
was primarily inﬂuenced by NT (Fig. 4). As
NT increased from 14 to 30 C with a 14 C DT.
leaf length decreased 32% (5.8 cm) (Table 2).
DT had little inﬂuence on leaf length. These
results contrast results of Friend and Pomeroy
(1970) on Triticum where leaf length ﬁrst in-
creased as temperature increased from 10 to
25 C then decreased with temperatures above
25 C. The differences in response of Lilium
and Triticum leaf length to temperatures above
25 C may be due to different temperature op-
tima for leaf growth in these two species.

Both DT and NT inﬂuenced ﬂower length
(Table 2). NT had a greater eﬂ‘ect on ﬂower
length than DT. As NT increased from 14 to
30 C with DT held at 14 C. ﬂower length de-

6

6
January 1989]

Leaf Length (cm)

 

 

 

 

 

 

 

Fig. 4. Response surface generated from predicted ﬁnal
leaf length of Lilium longrﬂorttm cm. Nellie White as in-
ﬂuenced by day and night temperature. Predicted leaf length
was based on the regression function 0.581132-DT +
-0.012254-DT= - -0.425519-.\'T 1 19.49 (r2 - 0.72).

creased 39% (2.4 cm). In contrast. as DT in-
creased from 14 to 30 C with NT held at 14
C. ﬂower length decreased 15% (1.2 cm).

The results presented in this paper deﬁne
thermomorphogenic responses in L. longt'jlo-
rum. Went and Bonner (1943) suggested that
thermomorphogenic stem elongation in LV-
capersicon esculenttmt resulted from an alter-
ation in the carbohydrate status in the elon-
gating region of the stern. Thermomorphogenic
stem elongation responses of Dendrothema
grandiﬂora (Chrysanthemum) (Karlsson and
Heins. 1986) and Lilium are similar. The sim-
ilar thermomorphogenic responses of these two
species showed that a supplemental carbohy-
drate source such as the Lilium bulb does not
inﬂuence stem elongation. The eﬂ'ect of tem-
perature on Lilium stem elongation was not
affected by increasing or decreasing the irra-
diance which plants were grown under between
50 and 400 umol s" rn'2 (Erwin and Heins,
unpublished data). The lack of differential
thermomorphogenic responses of L. longiﬂo-
rum to irradiance and the lack of a differential
response to temperature between Dendrothe-
ma and Lilium suggested that total carbohy-
drate availability within the plant is not the
primary factor responsible for the stern elon-
gation response to temperature as Went and
Bonner ( 1943) had suggested.

Our results would be compatible with Went
and Bonner‘s (1943) work if carbohydrate
availability were limited by translocation.
Translocation has been shown to increase ex-
ponentially in Glycine; as temperature in-

ERWIN er AL.—THERMOMORPHOGENES|S 1N ULIUM 51

TAaLe 3. The eject ofancymr‘dol and the day/night tem-
perature regime on Lilium longiﬂorum Thunb. plant
height at anthesis

 

 

 

Plant height
Temper- 0 50 mg
ature Plant ancymidol Percenr
regime (O DIF height (em) spray reduction
25/15 10' 48.2” 39.1‘ 19"
20/ 15 5 46.5 36.5 22“
15/15 0 36.0 30.4 16“
20/20 0 35.8 31.2 13‘
15/20 - 5 29.3 29.7 0 ns
15/25 -10 29.1 30.1 - 3 ns
' Numerals represent day temperature minus night tem-
perature.

‘ Numerals represent the treatment mean.

‘ Ancymidol was applied as two spray applications of
0.25 mg each. Applications were made 7 and 14 days after
ﬂower initiation.

‘ Signiﬁcant at P - 0.05(‘); P - 0.0“”); not signiﬁcant
(n51

creased from 5 to 40 C (Marowich. Richter.
and Hoddinoly. 1986). i.e.. translocation re-
sponds to absolute temperature. If carbohy-
drate translocation were the limiting factor in
determining the stem elongation response to
temperature in Lilium. stem elongation should
have increased or decreased as DT and NT
increased with a constant DIF. As is seen in
Fig. 2. this was not the case. In addition. ﬂower
bud abortion should have been negatively cor-
related with plant height since ﬂower bud abor-
tion is sensitive to carbohydrate depletion (Ei-
nert and Box. 1967). This was not the case 0.:
- 0.03). It is, therefore. unlikely that ther-
momorphogenic stem elongation responses are
a result of carbohydrate availability and/or car-
bohydrate translocation.

It is more likely that the eﬂ'ect of DT and
NT (DIF) on Lilium stem elongation is me-
diated through diﬂ‘erences in hormone synthe-
sis or action. probably gibberellin. Preliminary
results of experimentation studying the eﬂ'ect
of temperature on stem elongation responses
to a gibberellin biosynthesis inhibitor, ancy-
midol (Moore, 1979), suggested that there is a
strong interaction between DIF and the en-
dogenous levels of gibberellin within Lilium
(Table 3). The effect of the ancymidol appli-
cation on stem elongation decreased as DIF
decreased. In addition, application of GA...
can overcome the inhibition of stem elongation
induced by a negative DIF (N. Zieslin. personal
communication).

Morphological characteristics of Lilium
grown with a large positive DIF were similar
to morphological characteristics of plants with
low phytochrome photoequilibria. i.e.. grown

7

52 ' AMERICAN JOURNAL OF BOTANY

under far-red light (Holmes and Smith, 1977).
Similarly, the morphology of Lilium grown with
a negative DIF were similar to morphological
characteristics of plants with high phyto-
chrome photoequilibria. i.e., grown under red
light. Also, thermomorphogenic behavior ap-
pears to be much greater in plants which are
highly photoperiodic (e.g.. L. longtﬂorum.
Dendrothema grandtﬂora. E uphorbia pulcher-
rima. F ucshia hybrida) than plants which are
“day neutral" (e.g.. Tulipa hybrida. Narcissus
pseudonarcissus. C ucumis sativa) (Erwin and
Heins, unpublished data). The similarity in
thermomorphogenic and photomorphogenic
responses suggested that these two processes
may be related with respect to their perception
and/or transduction. Investigations have been
initiated to determine the possible interactions
between phytochrome and thermomorpho-
genic behavior in plants.

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DIXON. W. J. 1983. BMDP statistical software. Univer-
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DortLAND. R. F.. AND F. W. WENT. 1947. Plant growth
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EtNEttT. A. E.. AND C. O. Box. 1967. Effects of light
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Enwm. J. E.. AND R. D. l-lEth. 1985. The inﬂuence of
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[Vol. 76

Sequoia sempervirens (D. Don) Endl. and Pseudotsuga
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Homes. M. 6.. AND H. SMITH. 1977. The function of
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KAtttssON. M. 6.. AND R. D. 112th 1986. Response
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LECHARN'Y. A.. M. Scwwm. AND E. WAGNEtt. 1985. Stem
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MArtowtot. 1.. C. RtetrTEIt. AND J. HODDtNOLv. 1986.
The inﬂuence of plant temperature on photosynthesis
and translocation rates in bean and soybean. Canad.
J. Bot. 4: 2337-2342.

Mowseuse. S. R. AND F. W. Wm. 1958. Effects of
temperature on growth and dry matter accumulation
of peas. Pl. Physiol. 33: 372-374.

Moons. T. C. 1979. Biochemistry and physiology of
plant hormones. Springer-Verlag. New York.

ME. N. H. 1975. SPSS: statistical package for the social
sciences. McGraw-Hill. New York.

Nroxu. E. 1957. The eﬂ’ect of mineral nutrition and
temperature on leaf shape in lpumoea cacrula. New
Phytol. 56: 154-171.

ROBERTS. R. H. 1943. The role of night temperature in
plant performance. Science 1 143: 265.

SMITH. D. R..AND R.W. LANONANs. 1961. The inﬂuence
ofday and night temperatures on the growth and ﬂow-
ering of the Easter lily (Lilium longtﬂorum Thunb.
var. Croft). Amer. Soc. Hort. Sci. 80: 593-598.

VIGLIERCH10.D.R..ANDF. W.WENT. 1957. Plantgrowth
under controlled conditions. IX. Growth and fruiting
of the Kentucky Wonder bean (Phascolus i-ulgart's).
Amer. J. Bot. 44: 449—153.

WENT. F. W. 1944. Plant growth under controlled con-
dttions. ll. Thermoperiodicity in growth and fruiting
of the tomato. Amer. J. Bot. 31: 135-150.

. 1945. Plantgrowth under controlled conditions.

V. The relation between age. light. variety. and ther-

moperiodicity of tomatoes. Amer. J. Bot. 32: 469-

479.

. 1953. The effect of temperature on plant growth.

Annual Rev. P1. Physiol. 4: 347-362.

. AND D. M. Roma. 1943. Growth factors con-
trolling tomato stem growth in darkness. Arch. Bio-
chem. 1:439-452.

Wthth. H. F. 1973. Inﬂuence of temperature on the
development of ﬂower buds from the visible stage to
anthesis of Lilium longiﬂorum Thunb. cv. ‘Ace.’
Hortscience 8: 129-130.

 

Section II

Temperature Effects On Lily Development Rate

And Morphology From The Visible Bud Stage Until Anthesis

9
Temperature Effects On Lily Development Rate

And Morphology From The Visible Bud Stage Until Anthesis

John B. Irwin and Royal D. Reins

Department Of Horticulture
Michigan State University

East Lansing, MI 48824-1112

Additional Index Words: Lilium lgngiflgggm,
thermomorphogenesis, DIF, degree day, thermoperiodism, stem

elongation, plant development, flower bud abortion, plant

height, inflorescence development.

Received for publication . Mich. Agr.
Expt. Sta. No. 12677. The authors appreciate the assistance
of Cathey Fredenburg, James Eppink, and Sharon Strnad during
this project. Lily bulbs were donated by the Pacific Bulb
Grower's Association. This project was funded in part by a
grant from the Fred C. Gloeckner Foundation and The American
Floral Endowment. The cost of publishing this paper was
defrayed in part by the payment of page charges. Under postal
regulations, this paper must be hereby marked ggygggiggmgn;

solely to indicate this fact.

10
Abstract

Day temperature (DT) and night temperature (NT)
influenced 111111111 Mm Thunb. ‘Nellie White' stem
elongation and development rate from the visible bud stage
(VB) until anthesis (ANT). Plant height increase after VB was
a function of the difference (DIF) between DT and NT (DT-NT).
Plant height increased 90% as DIF increased from -16 to 16CL
A cubic model described bud development rate as a function of
temperature from 14 to 30 C. A linear model adequately
described bud development rate as a function of average daily
temperature (ADT) from 14 to 21CL Based on the linear model,
bud development rate increased .05 per day for each 1°C
increase in ADT. The base temperature for bud development,
i.e. the temperature at which bud development rate was 0, was

calculated as 3.5 C.

11
Introduction

Greenhouse forcing of vernalized Easter lilies, L111um
lgngiflgrgm Thunb., is commonly divided into 3 phases. These
phases are: I) placement of vernalized ‘bulbs in the
greenhouse to flower initiation, II) :flower initiation to the
visible bud stage (VB), and III) VB to anthesis (Al-l)
(DeHertogh and Wilkins, 1971). Plant morphological
development differs during each of the forcing phases
(DeHertogh and Wilkins, 1971). Growth during phase I is
vegetative and consists of stem elongation and leaf expansion.
Flower initiation, leaf expansion, and stem elongation occur
during phase II. Inflorescence expansion and stem elongation
occur during phase III.

Lily responses to temperature during phase III differed
from those during Phase I and II (Wang and Roberts, 1983).
Lily development rate, quantified as days to unfold a leaf, is
a decreasing linear function of average daily temperature
between 14 and 30 C during phase I and II (Karlsson et a1,
1988). Lily development rate during phase III is a nonlinear
function of temperature (Healy and Wilkins, 1984). The
effect of temperature on the rate of lily development
decreases as DT and/or NT increase during phase III (Roh and
Wilkins, 1973; Mealy and Wilkins, 1984).

Easter lily morphological development is
thermomorphogenic. For instance, internode length increases

as the difference (DIF) between day (DT) and night temperature

12
(NT), i.e. day temperature - night temperature, increases
(Erwin et al, 1989). In addition, leaf orientation, leaf
length, and flower length are also influenced by diurnal
changes in temperature.

Quantification of Easter lily responses to temperature is
useful to Easter lily growers. Selection of the proper
average daily temperature is critical to achieve a desired
rate of plant development so plants flower for a desired
marketing date. Improper selection of temperatures during
phases II and III may result in incorrect crop timing, flower
bud abortion (Roh and Wilkins, 1973) and/or excessively tall
or short plants at anthesis (Erwin et. al., 1989). Karlsson
et. al. (1988) developed a mathematical function relating the
rate of lily leaf unfolding to average daily temperature
during phase II. Similarly, Erwin et. al. (1989) determined
the functional relationships for the effects of DT and NT on
stem elongation and leaf orientation during phase II. Healy
and Wilkins (1984) developed functional relationships between
lily bud length and the time to flower of plants grown with
constant DT and NT during phase III. The functional
relationships describing the rate of lily development and stem
elongation for lily plants grown at different DT and NT during
phase III have not been determined.

The objective of this research was to develop
mathematical functions relating the rate of Easter lily

development and stem elongation to DT and NT during phase III.

13
Materials And Methods

Easter lily bulbs 17.7-20.3 cm in circumference were
planted in 15.2 cm (pot volume = 2,570 ml) plastic pots on 28
October, 1985, in a soilless medium consisting of equal parts
of sphagnum peat, perlite, and vermiculite. Potted bulbs were
placed in a greenhouse for two weeks where air temperature was
adjusted to maintain a medium temperature of 17 i 1 C to
encourage root development. Plants were then vernalized for
6 weeks at 5 C after which all plants were placed in a
glasshouse under natural photoperiodic conditions with
constant 20 C DT and NT temperature setpoints. Upon shoot
emergence, plants received a long day treatment for 7 days
consisting of the natural photoperiod (ca. 9 hr 15 min.) plus
a night interruption lighting from 2200 to 0200 hrs delivered

1 m'2 (400-700 nm

with incandescent lamps at a 2 umol s'
wavelength). Plants were returned to natural photoperiodic
conditions after the long day treatment.

Time of flower initiation was established by terminal
shoot dissections every 3 days on 5 randomly selected plants
starting 13 January, 1986. Flower initiation was defined as
the first visible differentiation of the vegetative meristem
into a reproductive meristem (DeHertogh et al, 1976, Figure
2c). Flower initiation was observed on 100 % of the sample on
22 Jan.

Plants were then selected for uniformity based on plant

height and leaf number and moved to greenhouses with

14
maintained at 14, 18, 22, 26, or 30 C. Actual average
temperatures during the experiment did not vary by more than
1.8 C from the desired temperature setpoints. Plants were
moved among greenhouses at 0800 and 1800 hr each day to yield
a total of 25 DT/NT treatment combinations. Each temperature
'treatment.had.5 single plant.replicates (total of 125 plants).

Movement of plants required approximately 30 min. An
opaque curtain was pulled over the plants at 1800 and was
retracted just prior to 0800 to provide a 14 hr scotoperiod to
parallel the night temperature treatment. Plants were spaced
at 11 plants mT.

Data were collected on the date and plant height at
visible bud and anthesis. Plant height was defined as the
height of the plant from the soil line to the tip of the
uppermost bud.

Analysis of variance ‘was conducted using the ANOVA
procedure of The Statistical Package Of The Social Sciences
(SPSS) (Nie, 1975). Regression analysis of the data were
conducted using the ‘All Possible Subsets Regression (P9R)'
and the ‘Stepwise Regression (P2R)' subroutines of the
‘Biomedical Statistical Software Package' (Dixon, 1983).
Models were selected based on evaluation of residuals, r2,
and Mallow's Cp (Draper and Smith, 1981). All parameters

selected in the models were significant at the P=0.05 level.

15
Results
Chang; in hgighg fzgm VB unti; anthesis: Change in plant
height after VB was a function of DIF between DT and NT (DT-
NT). Plant elongation after VB increased from 14.2 to 27.0 cm
as DIF increased from -16 to 16 C (Figure 1). The
relationship between DIF and stem elongation after VB is
consistent with previous lily research which showed a greater
effect of DIF on internode elongation during stage II than
absolute DT and/or NT (Erwin et. al., 1989). Kohl et. a1.
(1958) showed that plant heights were similar on lilies grown
at constant 21.1, 15.5, or 10 (2 (0 DIF) temperatures, as
expected if DIF controls elongation and not absolute
temperatures between 10 and 30 C. Roh and Wilkins (1973)
reported that stem.elongation after VB was only affected by DT
above 21.1 C. Regression of treatment means reported by Rob
and Wilkins with DIF as the independent variable and plant
height at anthesis as the dependent variable resulted in a
model with an rziof 0.63. This model would likely have had a
higher r2 if the regression was based the change in height
after VB only as treatments were only initiated following VB
and a significant amount of stem elongation had occurred prior
to VB. These data, however, are not reported. Our results
contradict the results of Smith and Langhans (1962) who stated
that DT and NT did not affect plant height during

developmental stages II and III.

16
v lo e V t' s' : The time from VB to
anthesis decreased as either DT or NT increased from 14 to 26
C (Table 1). The minimum time from.VB to anthesis was 26 days
when plants were grown at constant 26°C. These data are
comparable to results of Roh and Wilkins (1973) who reported
a minimum time of 24 days with Easter lily cv Ace grown at
constant 32 C.
Lily flower bud development rate was a quadratic function
of temperature when DT and NT were held constant (Figure 2).
Maximum flower development rate was observed near 26 C. The
maximum near 26 C is similar to that of wheat and maize where
the maximum leaf unfolding rate occurred between 25 and 30 C
(Alm et. al., 1988; Tollenaar et. al., 1979; Warrington and
Karemasu, 1983) . The temperature optimum for flower bud
development is lower, however, than for lily leaf unfolding
.which is above 30 C (Karlsson et. al., 1988).

When DT and NT were not identical, daily flower bud
development rate was the mathematical sum of the hourly flower
bud development rates at the temperatures which plants were
grown under. Figure 2 shows straight lines connecting to 30
DT/30NT treatment development rate with the 14 DT/14 NT, 18
DT/18 NT, 22 DT/22 NT, and the 26 DT/26 NT development rates.
These lines represent the expected flower development rates
for all average daily temperatures created by the DT and NT
combinations of the temperatures connected by a line. Data

points of actual development rates of plants from treatments

17
with temperature combinations associated with the lines show
actual rates of development are close to predicted rates.
The prediction model for development rate was based on a
10-hr day and a 14-hr night period. This model can be

modified for any length of day;

Daily Rate =

b2*( (HDT*DT)+(1~INT*NT) ) b3*HDT*DT3 b‘*HNT*NT3

where b1, b2, b3, and b,’ are parameter coefficients. HDT and
HNT are hours of day and night, respectively.
The model can be further modified to directly calculate

hourly development rate at a specific temperature;

Hourly rate =
b1+b2*T3+(b3+b,.)*T3
-- --------------------- (2)
24 24 24
where T is the hourly temperature.
When either DT or NT do not exceed 22 C, daily flower

development rate can be approximated by a linear function

based on average daily temperature (ADT);

daily rate = -0.740904E-02 + (0.209036E-02 * ADT) . (3)

A linear ADT model can be used because development rate

is nearly linear in the 14 to 22 C temperature range (Figure

18
2). When development rate is a linear function of ADT, a
degree day model can be used (Karlsson et a1, 1988). From
function (3), 478 degree days are required above a base
temperature of 3.5 C for lily flower bud development from VB
to FLW. This base temperature calculated for flower bud
development is comparable to the base temperature for lily

leaf unfolding, 1 C (Karlsson et al., 1988).

19

Literature Cited

Alm, D.M., D.R. Pike, J.D. Hesketh, and E.W. Stoller. 1988.

Leaf area development in some crop and weed

species. Biggggnigs 17:29-39.

Dixon, W.J., 1983. BMDP Statistical Software. Univ. of

Calif. Press., Berkely, CA. pp. 251-277.

De Hertogh, A.A., and H.F. Wilkins. 1971. The forcing of
northwest-grown ‘Ace' and ‘Nellie White' Easter

lilies. £122: Bgv. 149:29-31, 57, 104-111.

De Mertogh. A.A., H.P. Rasmussen, and N. Blakely. 1976.

Morphological changes and factors influencing shoot

apex development of m M Thunb.

during forcing. J. Amez. Soc. ﬂogt. Sg1., 101:463-
471.

Draper, N.R., and H. Smith. 1981. Applied regression
analysis. 2nd Ed., John Wiley and Sons, Inc.

N.Y., N.Y. pp. 294-313.

Erwin, J.E., R.D. Meins, and M.G. Karlsson. 1989.

Thermomorphogenesis in 1.1111113 Mm Thunb.
Amer, J, Bot,, 76:47-52.

20
Friend, D.J.C, V.A. Helson, and J.E. Fisher. 1962. Leaf
growth in marquis wheat, as regulated by

temperature, light intensity, and daylength. Can.

J. 391., 40:1299- 1311.

Healy, W.E. and H.F. Wilkins. 1984. Temperature effects on

‘Nellie White' flower bud development.

Hortscience, 19:843-844.

Karlsson, M.G., R.D. Heins, and J.E. Erwin. 1988.
Quantifying temperature controlled leaf unfolding
rates in L1112m loggiflggum Thunb. ‘Nellie White'.
J. Amgz. Soc, 391;. 591,, 113:70-74.

Kohl. H. 1958. Effects of temperature variation on forced

Liliua_leagiflgrua var ‘Ace'. J. Ame . .
S911, 72:477-480.

Nie, N.H. 1975. SPSS: Statistical Package For The Social
Sciences. version 10.00. McGraw-Hill Pub. Inc.,

N.Y., N.Y. pp. 398-433.

Roh, S.M., and H.F. Wilkins. 1973. Influence of temperature
on the development of flower buds from the visible

bud stage to anthesis of Liligm lgngiflgggm Thunb.
cv. ‘Ace'. Hortsgiegce, 8:129-130.

21
Smith, D. and R. Langhans. 1962. The influence of day and
night temperatures on the growth and flowering of
the Easter lily (W Thunb. var
‘Croft'). J. Ameg. Soc. Hozg. Sg1., 80:593-598.

Tollenaar, M., T.B. Daynard, and R.B. Hunter. 1979. Effect
of temperature on rate of leaf appearance and

flowering date in maize. Qrgp §g1., 19:363-366.

Wang, Y.T., and A.N. Roberts. 1983. Influence of air and
soil temperature on the growth and development of
Lgl1gm longiflorum Thunb. during different growth

phases. r. Soc. 0 t. '., 108:810-815.

Warrington, I.J., and E.T. Kanemasu. 1983. Corn growth
response to temperature and photoperiod II. Leaf-
initiation and leaf appearance rates. Agron, J.,

75:755-761.

22
Table 1. The influence of day and night temperature on the

number of days from visible bud to open flower in L111gm

Longiﬁlggum cv ‘Nellie White'.

Day Temperature (°C)

 

Night -------------------------------------------
Temperature (°C) 14 18 22 26 30
14 41.5 1 38.4 31.0 31.2 32.0
18 38.6 33.2 31.0 29.8 29.3
22 34.8 30.8 27.5 26.8 26.4
26 32.8 30.8 27.2 25.6 25.6
30 31.2 28.8 26.4 26.2 25.7

Day Temperature

Night Temperature

 

significant (n.s.)

Linear *** V Linear ***
Quadratic *** Quadratic ***
Cubic n.s. Cubic n.s.

‘ Numerals represent treatment means.

V Significance of data at P = .001 (***), not

23

Figure 1. Relationship between Lilium_lgggi£lgrym,cv
‘Nellie White' height increase during phase III and the

difference between the day and night temperature (DT-NT) .
Squares represent the mean change in plant height after
visible bud for each temperature treatment as determined
from 5 plants. The solid line represents the function
Height increase after visible bud = (0.496946*DIF) +

(0.150561*DIF2) + 18.01 (r2 = 0.77).

24

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25

Figure 2. Wm ‘Nellie White' bud development
rate per hour as a function of temperature. The

regression model is based on the function, Daily rate =
b1 + b2 * ((HDT * DT) + (HNT * NT))/24 + 133/10 * HDT * m3
+ 134/1“ * HNT * NT3 (r2 = .96). 8,, b2, b3, and b‘ are
parameter coefficients. HDT and HNT are hours of day and
night temperature, respectively. The bars associated
with the data points represent deviation between observed

and expected flower development rate.

26

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27

Section III.

Temperature And Photoperiod Effects On
Eugh§1g_g_gybrigg Morphological Development

28

Temperature And Photoperiod Effects on

Euchsia x hybriga Morphology

1 0 ° 0 2

w'
Department Of Horticulture
Michigan State University

East Lansing, MI 48824-1112 0.8.1.

Additional Index Words: thermoperiodism, thermomorphogenesis,
stem elongation, branching, leaf area, photoperiod, DIF,
phytochrome.

Received for publication . The authors
appreciate the assistance of Brian Kovanda, Joy Hind, Martin
Stockton, Mark Smith, and Wendy Cole. Fuchsia plants were
donated by Green Circle Growers of Oberlin, Ohio.
Acknowledgement is made to the Michigan Agriculture Experiment
Station, and The American.Floral Endowment for support of this
project. The cost of publishing this paper was defrayed in
part by payment of page charges. Under postal regulations,
this paper must be hereby marked advertisement solely to
indicate this fact.

1 Current address: Department Of Horticultural Science, The
University Of Minnesota, 1970 Folwell Ave, St. Paul,
Minnesota, 55108.

2

Current address: Department Of Horticulture, The

Agriculture University Of Norway, Aas, Norway.

29
Abstract

Eughsia x hybriga ‘Dollar Princess' plants were grown
under 41 different day/night temperature (DT/NT) environments
over a 2 year period with temperatures ranging from 10 to 30
C. Plants were grown under short days (9-hr photoperiod) or
long days (9-hr photoperiod plus a 4-hr night interruption)
within each environment. The relationship or difference (DIF)
between DT and NT (DT - NT) influenced Euchsia stem elongation
and leaf expansion more than absolute DT and NT between 10 and
24 C. Both internode length and leaf area increased linearly
as DIF increased from -14 to +14 C with DT and NT between 10
and 24 C. Internode length increased an average of 0.071 cm
and leaf area increased an average of 400 cm? per leaf per 1
C increase in DIF. DT or NT above 24 C reduced stem
elongation and leaf expansion, regardless of DIF. The
response of stem elongation and leaf expansion to DIF was
greater on a percent basis when plants were grown under short
days and long days, respectively. cnnan absolute basis, both
internode length and leaf area were greater on long day grown
plants. Branching increased as average daily temperature
decreased from 30 to 10 C. Photoperiod did not affect

branching.

30
Introduction

Plant morphology is thermomorphogenic in many plant
species (Erwin et al., 1989; Erwin, 1990a). The effects of
temperature on plant growth have historically been ascribed
solely to absolute temperature (Went, 1952). Recent
experimentation showed that morphological development of some
plants is influenced primarily by the relationship between day
(DT) and night temperature (NT), i.e. independent of absolute
temperature within a limited temperature range (Erwin et al.,
1989; Moe and Heins, 1990). For instance, Lilium lomgiflorum
stem elongation and leaf orientation were best described by
the difference (DIF) between DT and NT (DT - NT) rather than
absolute DT and NT between 10 and 30 C (Erwin et al., 1989;
Erwin and Heins, 1990b) . As DT increased relative to NT, i.e.
as DIF increased, Lglimm stem elongation increased and leaf

orientation became more upright. Similarly, Streptogarpus

mobilis, zamthium stromimm, Lygopersicum esculentum, Zea
maize, Salvia splendems, Impatiens wallerigmg, Nepmrolepis
mm (Erwin, 1990a; Erwin et al., 1990c), Eupmgrbia

pulgherrima (Berqhage. 1989). Dendrantheme (Karlsson et al.,
1989), and ngpgmmla isopmylla (Moe and Heins, 1990) stem

elongation were best described by DIF, and increased as DIF

increased within the 10 - 30 C temperature range.
Correlative evidence suggests that thermomorphogenic

responses may be mediated by or interact with phytochrome to

elicit growth responses (Erwin et al., 1989; Erwin, 1990a;

Mc
en
si
re

in

4f

te

31

Moe and Heins, 1990). Plants grown under positive DIF
environments (higher DT than NT) appear morphologically
similar to plants irradiated with lighting consisting of a low
red (660 nm):far-red (720 nm) ratio; plants have long
internodes and an upright leaf orientation. Conversely,
plants grown under negative DIF environments (higher NT than
DT) appear similar to plants irradiated with lighting with a
high red:far-red ratio; plants have short internodes and a
horizontal leaf orientation.

In addition to indirect evidence for phytochrome
involvement, there is an interaction between DIF and light
quality (Erwin, 1990a; Moe and Heins, 1990). Incandescent
lighting (low R:FR ratio) during the night period can overcome
inhibition of stem elongation by a negative DIF environment in
Campanmlg isgpnyng (Moe and Heins, 1990). In contrast,
fluorescent lighting (high R:FR ratio) during the night period
enhanced the inhibition of Campanula elongation which resulted
from growing plants in a negative DIF environment. An
interaction between light quality and DIF suggests that
phytochrome is involved in perceiving and/or interacting with
DIF to affect plant growth.

An understanding of how photoperiod and DIF interact to
affect plant stem elongation may result in alternative
methods of plant height control in controlled environments
which utilize both light and temperature to control plant

growth. The objective of the research conducted in this study

32
was to determine if DIF and photoperiod extension through
night interruption lighting interact to affect plant
morphology. 121199.519. was chosen for these studies because
Eucmsie exhibits a strong stem elongation response to DT and
NT (Tageras, 1979), and the effect of photoperiod on Eucheia
stem elongation has been studied extensively (Vince-Prue,

1977).

Materials And Methods
19§8 Experiment: Euchsia x hybrida ‘Dollar Princess' (fuchsia)
rooted cuttings were planted in 12.7 cm (volume = 390 cmﬁ)
plastic pots on 2 Jan., 1988, in a soilless medium consisting
of equal parts of sphagnum peat, perlite, and vermiculite.
Plants were grown for 2 weeks in a glasshouse under natural
photoperiodic conditions and maintained at 20 1 2 C air
temperature. Plants were then selected for uniformity based
on leaf number, plant height, and lateral shoot number, and
moved to glasshouses maintained at 12, 16, 20, and 24 C. Half
of the plants within each glasshouse, 24 plants, were grown
under short days (SD) which consisted of a 9 hour photoperiod.
The other half of the plants received a long day treatment
(LD) which consisted of a 9—hr photoperiod plus night
interruption lighting from 2200 to 0200 hr delivered with
incandescent lamps at an irradiance of 2 umol‘m'2 5”.

Plants were moved among the 4 glasshouses at 0800 and

1700 hr each day to yield a total of 16 DT/NT environments

wi

 

CC

0?

th

pr

p0

wa

tl’.

th

AV

tr

33

within. each. photoperiod. Each. environmental treatment
contained 6 samples. Movement of plants required 15 min. An
opaque curtain was pulled over the plants at 1715 hr after
they were moved at 1700 hr and was retracted at 0800 to
provide a photoperiod paralleling the thermoperiod. Light
pollution between LD and SD plants within a glasshouse section
was eliminated by pulling an opaque curtain between plants at
1715 hr and retracting the curtain at 0800 hr. The uppermost
unfolded leaf pair on each plant was marked with black ink to
identify the developmental stage of each plant when the
experiment was initiated.

Glasshouse temperatures were controlled using a
glasshouse climate control computer and monitored by a
datalogger using iron/constantan thermocouples. Actual
glasshouse section temperatures were determined by
thermocouple readings taken every 10 sec by a datalogger which
then calculated mean glasshouse temperatures every 2-hr.
Average DT and NT were calculated for each environmental
treatment based on bihourly temperature means and the length
of time ‘which. plants 'were grown ‘within an environment.
Average OT and NT did not vary by more than 2 C from the
temperature setpoints over the course of the experiment (Table
1). All plants were within 2 m of thermocouples during the
experiment Treatments are described by treatment setpoints
throughout the paper. Actual temperatures were used in

regression analysis.

 

91

34

Internode length, leaf length and width, and lateral
shoot number were collected at anthesis on plants grown under
LD, and after 78 days on plants grown under SD. Internode
length was collected from the second internode above the
marked leaf pair. Leaf length and width were collected from
a leaf at the base of the second internode above the marked
leaf pair. Since leaves were elliptic in shape, leaf area was
estimated by the formula for the surface area of a standard

ellipse: leaf area = (leaf length/2) * (leaf width/2) * 3.718.

12§2_£zpe;imem§;, The 1988 experiment was replicated with the
following changes:
1) Temperature treatments were started on 22 Oct.,
1988.
2) Terminal shoots were removed twice prior to the
start of treatments.
3) Glasshouse sections were maintained at 10, 15, 20,
and 25 C.
4) Three addition temperature environments were added;
10 C DT/30 C NT, 30 DT/lo C NT, and constant 30 C.
5) Data were collected after 74 days on plants grown

under SD.

Data were analyzed for both experiments by analysis of

variance (ANOVA) using a 4 x 4 x 2 factorial model with DT,

IH

54

r 4
W».

35

NT, and photoperiod as the main factors. Interaction terms
could not be evaluated through ANOVA as each temperature
treatment constituted a single replicate. The relative
importance of individual environmental parameters in affecting
morphological development was evaluated through multilinear
regression analysis. Selection of functions was based on r2,
Mallow's Cp (Draper and Smith, 1981), significance of
parameters, and visual inspection of the fit of the regression
function with the data.

The functional relationships between DIF and internode
length and leaf area were best described with linear
regression analysis. Interactions between DIF and photoperiod
were evaluated by analyzing differences between slopes of the
regression functions. Statistical analysis of differences
between slopes and elevations among regression functions
followed the procedure reported by Snedecor and Cochran
(1967).

Results
I. Intermeee Length: Fuchsia internode length was affected
by photoperiod and temperature. Internode length, averaged
over all treatments, was 142% greater on plants grown under
LD than plants grown under SD (Table 2) . Absolute differences
ranged from 0 to 3.4 cm.

Internode length increased as DT increased and/or NT

decreased (Table 2) but was best described by DIF (Figure 1) .

Internode length increased as DIF increased when absolute

36

temperatures ranged from 10 to 26 C (Figure 1). Internode
length increased from 2.5 to 6.2 cm as DIF increased from -15
to 16 C on LD grown plants in the 1989 experiment. Increasing
DT above 24 C reduced fuchsia internode length, regardless of
DIF (Table 2). For example, internode length decreased from
6.2 to 4.1 cm as DT increased from 24 to 30 C with a 10 C NT
on LD grown plants in the 1989 experiment even though DIF
increased from 15 to 20 C.

Slopes of regression functions ( b1 ) representing the
effect of DIF on internode length when temperatures ranged
from 10 and 24 C were not significantly different between the
1988 and 1989 experiments (Table 3). Therefore, data from
each photoperiod were combined across years by normalizing
data based on the difference in elevation ( b3 ) between the
functions (Figure 2). This was done by adding 0.266 (1.861-
l.595) to 1988 SD means and -0.447 (4.281-4.728) to 1988 LD
means.

DIF and photoperiod interacted to affect stem elongation
as shown by a significant difference between slopes ( kn ) of
the functions in Figure 2, i.e. between LD and SD plants
(Table 3). Plants grown under SD showed a lesser response to
DIF on an absolute basis but a greater response to DIF on a
percent basis than plants grown under LD. For instance,
internode length increased 326% and 224% as DIF increased from
-14 to 149C when plants were grown under SD and LD,

respectively.

[*1

3‘:

C3
a

37
11, Leaf Size; Leaf size was affected by photoperiod and
temperature. Leaf area, averaged over all treatments, was 22%
greater on plants grown under LD than plants grown under SD
(Table 4). Absolute differences ranged from 0.1 to 7.0 cm2
per leaf.

As with stem elongation, leaf area increased as DT
increased and/or NT decreased (Table 4) but was best described
by DIF (Figure 3). Leaf area increased from 7.3 to 15.4 cm2
(+111%) as DIF increased from -15 to 16 C on LD grown plants
in the 1989 experiment. As with stem elongation, DT above 24
C reduced leaf expansion (Table 4). Increasing DT from 24 to
30 C decreased leaf area from 15.4 to 7.9 cm2 (-49%) on LD
grown plants even though DIF increased from 14 to 20 C.

Slopes of regression functions ( b1 ) representing the
response of /leaf expansion to DIF were not significantly
different between 1988 and 1989 within photoperiod treatments
(Table 5). Therefore, data from each photoperiod. were
combined across years by normalizing data based on differences
in elevation ( bo ) between functions (Figure 3). This was
done by adding 0.256 (12.949-10.390) to 1989 SD means and -
0.447 (4.281-4.728) to 1988 LD means.

Slopes of functions representing the response of leaf
expansion to DIF between LD and SD grown plants were
significantly different indicating an interaction between DIF

and photoperiod (Table 4). In contrast to stem elongation,

plants grown under LD showed a greater response to DIF on a

38
percent basis (Table 4, Figure 3). Leaf area increased 249%
and 289% as DIF increased from. ~15 to 16 C on SD and LD grown

plants, respectively.

II . ' :

Lateral shoot development was primarily influenced by
ADT. Lateral branch number per plant decreased as ADT
increased from 12 to 24 C, regardless of photoperiod (Table 6,
Figure 4). For instance, the number of lateral branches per
plant decreased from 11.5 to 4.5 branches (~61%) as ADT
increased from 12 to 24 C on LD grown plants in the 1988
experiment. Photoperiod had no significant effect on lateral

branching.

Discussion

Stem elongation on reproductive (LD) plants was greater
than on vegetative (SD) plants. This was not unexpected as
fuchsia internode elongation is affected by 3 photoperiod
related factors: 1) fuchsia is a long day plant and stem
elongation increases after flower induction (Wilkins, 1985),
2) internode length increases as photoperiod increases
(Wilkins, 1985), and 3) internode length increases as the
red/ far red content of the last light exposure prior to
darkness decreases (Vince-Prue, 1977). Irradiating plants
with a night interruption (NI) of incandescent light (low

R:FR), as in this experiment, increased stem elongation

39

through one or more of these three factors. Internode
length was a function of the relationship between DT and NT
within a limited temperature range. Internode length
increased as DT increased and NT decreased as has been
reported previously on other plant species (Tageras, 1979;
Karlsson et al., 1989; Erwin et. al., 1989; Berghage et.
al., 1989; Moe and Heins, 1990). The effect of temperature
on stem elongation could be described more comprehensively
with the term DIF than by absolute DT or NT as previously
shown on Lelimm (Erwin et. al., 1989; Erwin et. al., 1990)
and gemeemm1e_ieepmylle (Moe and Heins, 1990). While original
research by Went (1957) suggested that plant stem elongation
was primarily influenced by DT, our measurements of internode
lengths from photographic plates of Eisum eativum plants in
‘his original article» showed internode length. was indeed
strongly influenced by DIF.

The transduction.pathway for the effects of DIF on stem
elongation is believed to involve gibberellin (GA) synthesis
(Zieslin and.Tsujita, 1988, Erwin et al., 1989; Moe, personal
observation). Application of gibberellins (GAHJ) to Lilimm
bulbs prior to planting overcame subsequent inhibition of stem
elongation by a negative DIF environment (Zieslin and Tsuj ita,
1988). Similarly, Moe and Heins (1990) showed that spray
applications of GA3 overcame inhibition of WW};
stem elongation when plants were grown in a negative DIF

environment. In contrast, application of a GA synthesis

40
inhibitor, ancymidol (alpha-cyclopropyl-alpha-(4-
methoxyphenyl)~5~pyrimidinemethanol) , resulted in a greater
percent decrease in stem elongation of positive DIF grown
plants than negative DIF grown Lilimm plants (Erwin et al,
1989) . An interaction between DIF and GA action on stem
elongation is, therefore, apparent.

Both gibberellins (Jones and Zeevaart, 1980; Pharis
and King, 1985) and DIF (Erwin, 1990a) affect sex expression
in the dioecious family Cucurbiteeeae. Application of
gibberellins to Agrostemma causes maleness (Jones and
Zeevaart, 1980; Pharis and King, 1985). In contrast,
application of GA synthesis inhibitors induces femaleness in
muskmelon (Halevy and Rudich, 1967; Pharis and King, 1985).
Plants grown in a positive DIF environment have more male
.flowers than female flowers. Conversely, plants grown under
a 0 or a negative DIF environment have equal or more female
flowers than male flowers (Erwin, 1990a). Although other
factors can influence sex expression in Cucurbitaceae, such as
ethylene, these results combined with previous data provide
additional evidence that a positive DIF environment may
promote GA synthesis and/or that a 0 or negative DIF
environment may reduce GA synthesis. DIF, therefore, appears
to influence the endogenous levels of biologically active
gibberellins. Alternatively, a 0 or negative DIF environment
may stimulate synthesis of an elongation inhibitor or promote

GA degradation.

41

DIF and photoperiod interacted to affect stem elongation
in this study where night interruption lighting with
incandescent lamps was used. The question arises as to
whether the interaction between temperature and photoperiod is
due to a response to light. quality or light duration.
Berghage (1989, personal observation) showed that increasing
photoperiod via a day extension treatment using white light
also resulted in a photoperiod x DIF interaction. Therefore,
a DIF x photoperiod interaction is present independent of a
light quality effect. The data presented in the current
research and that of Berghage (1989, personal observation)
both showed a greater response of stem elongation to DIF on a
percent basis on SD grown plants than LD grown plants.

DIF strongly influenced leaf expansion. The effect of
DIF on fuchsia leaf expansion contrasts previous research on

Lilimm_lemgiflermm,*where leaf expansion was a function of NT
only (Erwin et. al., 1989). Earlier work by Dale (1964)

suggested that Eneeeolms ymlgezis leaf expansion was greatest
when DT and NT were constant, i.e. a 0°C DIF. Our

reexamination of Dale's data (1964) showed this conclusion was
based on a number of treatments which contained either a 30 C
DT or NT. Based on Dale's own data and conclusion's (1964),
leaf expansion was reduced at 30 C. Therefore, conclusions
relating temperature effects and leaf expansion based on 30 C
temperature treatments may be misleading. If Dale's data

(1964) from environments not containing a 30 C DT and/or NT

42

are eliminated, leaf area increased as DIF increased. The
greatest leaf area occurred in the environment with the
highest DIF which did not contain a 30 OT or NT (20 C DT/10 C
NT). In contrast, recent research by Erwin and Strefeler
(1990, personal observation) showed that gmemmie leaf
expansion was greater when plant were grown with constant
temperatures versus fluctuating temperatures. Greater leaf
expansion in a positive DIF environment or a constant
temperature environment is probably species dependent.

Leaf expansion is often influenced by ADT as has been
shown in Emeseelus (Dale, 1964), Qmemmie (Milthorpe, 1959),
and EBEDQIDiQ (Berghage, 1989). No response of fuchsia leaf
expansion to ADT was observed in the current study.

Branching in Ememsia decreased as ADT increased. A
decrease in lateral branching as ADT increased had also been
reported on Petunia (Kaczperski et. al., 1989) and Qiamtmms
(Moe, 1983).

Night interruption lighting using incandescent lighting
has been shown to reduce lateral branching on nemgmemgneme
(Heins and Wilkins, 1979a), gempemmle (Moe and Heins, 1990),
and Qiemﬂme (Heins and Wilkins, 1979b) when compared to
plants which received no NI or received a day extension
treatment. Heins and Wilkins (1979a, 1979b) suggested that
the reduction in lateral shoot number'was due to inhibition of
lateral shoot breaking by far red light and/or induction of

flowering, as was the case with.Qiem§hus. Flower induction of

43
fuchsia did not significantly affect branching in the current

study.

44

Literature Cited

Berghage, R.D. 1989. Modeling stem elongation in Emmnemmie
pmlenemzime. PhD Thesis. Michigan State University.

Dale, J.E. 1964. Some effects of alternating temperature on
the growth of French bean plants. n . o , N.S.

28 (109) :127-135.

Dale, J.E., 1965. Leaf growth in ghaseolus vulgamis. II.
Temperature effects and the light factor. Amm, Bot.

29:293-308.
Erwin, J.E., R.D. Heins, and M.G. Karlsson. 1989.
Thermomorphogenesis in Lilium lomgiflerum. Amer. J. Bot.

76(1):47~52.

Erwin, J .E. 1990a. Thermomorphogenesis in plants. PhD

Thesis, Michigan State University.

Erwin, J .E. 1990b. Temperature effects on lily development

rate and morphology from the visible bud stage until

anthesis. £1.8merl_§221_ﬂertl_§211. 115(4)=(in preSS).

45
Erwin, J.E., R.D. Heins, and B.J. Kovanda. 1990c.

Thermomorphogenic and photoperiodic responses of

Nsnhrgleni§_exaltata. 8232.82121. (in press)-

Halevy, A.H., and J. Rudich. 1967. Modification of sex
expression in muskmelon by treatment with the growth

retardant B~995. REALM 20:1052-1058.

Heins, R.D., and H.F. Wilkins. 1979a. The influence of node
number, light source, and time of irradiation during
darkness on lateral branching and cutting production ni
‘Bright Golden Anne' Chrysanthemum. J c r .

§ci., 104(2):265-270.

Heins, R.D., and H.F. Wilkins. 1979b. The effect of
photoperiod on lateral shoot development in [21 emtmus
W L. cv. ‘Improved White Sun'. J, Amer, Soe.
Hertl_§211. 104(2):314-319.

Jones, M.G., and J.A.D. Zeevaart. 1980. The effect of
photoperiod on the levels of seven endogenous
gibberellins in the long—day plant W L.
Elengg 149:274-279. '

46
Karlsson, M.G., R.D. Heins, J.E. Erwin, R.D. Berghage, W.H.
Carlson, and J .A. Biernbaum. 1989. Temperature and
photosynthetiijhoton flux influence Chrysanthemum shoot
development and flower initiation under short-day

conditions. W 114(1) =158-163-

Kaczperski, M.P. 1989. Influence of temperature and
irradiance on growth and development of Eetmmia 3 112221 da

‘Snow Cloud'. M.S. Thesis. Michigan State Univ.

Loach, K. 1970. Shade tolerance in tree seedlings. II.

Growth analysis of plants raised under artificial shade.

Neg Enygol. 69:273-286.

Milthorpe, F.L. 1959. Studies on the expansion of the leaf
surface. I. The influence of temperature. J. 0

52:1. 10(29):233-249.

Moe, R. 1983. Temperature and daylength responses in
W CV- Napoleon 111- 1919412111.

141:165-171.

Moe, R., and R.D. Heins. 1990. Control of plant
morphogenesis and flowering by light quality and

temperature. Aete Homt., (in press).

47
Pharis, R.P., and R.W. King. 1985. Gibberellins and
reproductive development in seed plants. W

W 36:517-568.

Snedicor, G.W., and W.G. Cochran. 1967. Statistical methods.

6th edition. The Iowa State Univ. Press, Ames, Iowa. pp.

432-436.

Tageras, H. 1979. Modifying effects of ancymidol and

gibberellins on temperature induced elongation in 3191151;

3.11m. Mom. 91:411-417-

Vince-Prue, D., 1977. Photocontrol of stem elongation in

light-grown plants of W Planta 133:141-

156.

Went, F. W. 1957. The experimental control of plant growth.

Chr. Bot. 17. The Ronald Press Co., N.Y., N.Y., pp. 223-

226.

Went, F.W. 1952. The effect of temperature on plant growth.

WM 4:347-362.

Wilkins, H. 1985. Wide in CRC Handbook of

Flowering, Vol III., ed. A.H. Halevy, CRC Press, Inc.,

Boca Raton, Florida, pp. 38~41.

48
Zieslin, N., and M.J. Tsujita. 1988. Regulation of stem

elongation of lilies by temperature and the effect of

gibberellin. §£i§ﬂ£§i§.ﬂ§££l 37:165-169.

49

Table 1. Temperature setpoints and actual average day (DT) and night (NT)

temperatures (DT/NT) for all environmental treatments for 1988 and 1989.

 

DT Setpoint (°C)

 

 

NT -
Setpoint (°C) 12 16 20 24
1988 Actual Temperature (DT/NT)
12 14/12 18/12 21/12 25/12
16 14/17 17/17 21/16 25/17
20 14/20 17/20 21/20 25/20
24 14/24 17/24 21/24 26/24
10 15 20 25 30
1989 Actual Temperatures
10 11/10 15/10 19/10 24/10 30/10
15 11/15 15/15 19/15 24/15 ~
20 ll/20 15/20 19/20 24/20 ~
25 ll/25 15/25 19/25 24/25 ~
30 11/31 ~ ~ ~ 30/31

 

 

 

50

Table 2. The effect of DT, NT and photoperiod on £22h§i£_£5h22£i§2 ‘Dollar
Pr incess' internode length at anthesis. LD were delivered as a 9~hr

photoperiod plus a 4~hr night interruption using incandescent lamps at an

1

irradiance of 10 umol s' ufz. SD were delivered as a 9~hr photoperiod

 

 

 

 

 

only.
DT (°C) Treatment
NT (°C) _____________
Treatment 10 15 20 25 30
10
LD - 1 4.8 5.6 6.2 4.1
SD 1.0 1.4 2.2 3.4 2.9
15
L0 3.3 4.7 5.1 5.2 -
SD 0.9 1.4 2.3 3.2 ~
20
LD 3.3 3.7 4.3 4.7 ~
SD 0.6 1.1 2.0 2.7 ~
25
L0 2e5 2e9 305 3e8 -
SD Dog 103 1.8 2e6 -
30
Lb 1.6 - - - 1.8

SD 1.0 -' - - leg

51

Table 2 ~ continued

 

Day Temperature *** V
Linear ***
Quadratic n.s.
Cubic n.s.
Night Temperature ***
Linear ***
Quadratic n.s.
Cubic n.s.
Photoperiod ***
z Numerals represent treatment means from 1989
experiment.
V Significance of both 1988 and 1989 experiments combined at P = .001

(***), not significant (n.s.).

Table 3.
of .Eushsia_JL_hxh£ida

52

‘Dollar Princess '

Regression coefficients calculated to predict internode length

plants from experiments

conducted during 1988 and 1989 studying the effect of DT, NT, and

photoperiod on plant morphology.

Comparison of

slopes and

intercepts were evaluated using the technique outlined by Snedicor

and Cochran (1967).

 

 

 

Normalized Data Regression

 

4.727
0.129
0.867

“.8.

***

***
*tt

*i*

Raw Data
SD LD
Coefficients 88 89 88 89 SD
bo 1.595 1.861 4.728 4.281 1.871
b1 0.067 0.073 0.124 0.132 0.071
r2 0.884 0.572 0.696 0.964 0.644
Comparison Of Slopes
Raw data 88 SD versus 89 SD F - 1.5 (df=1,31)
Raw data 88 LD versus 89 LD F = 3.6 (df=l,30)
Normalized data SD versus LD F a 36.9 (dfal,61)
Comparison Of Intercepts
Raw data 88 SD versus 89 SD F = 9.2 (df-1,33)
Raw data 88 LD versus 89 LD F - 12.3 (df81,32)
Normalized data SD versus LD F = 441.8 (df81,65)

53

Table 4. The effect of DT, NT and photoperiod on Ememege m hybrida ‘Dollar

Princess' single leaf area at anthesis. LD were delivered as a 9
hour photoperiod plus a 4 hour night interruption delivered using
incandescent lamps at an irradiance of 2 umol s'1 m'z. SD were
delivered as a 9 hour photoperiod only. Leaf area was calculated by
measuring leaf length and width and calculating the area of an

ellipse, i.e. leaf area a (width/2) * (length/2) * 3.78.

 

DT (°C) Treatment

 

 

 

NT (°C) - ------------
Treatment 10 15 20 25 30

10

LD - 1 18.4 16.6 15.4 7.9

SD 8.9 11.4 10.9 12.1 7.1
15

LD 10.3 13.5 18.5 15.5 ~

SD 8.8 9.4 14.8 12.8 -
20

L0 7.4 10.1 13.7 12.7 ~

SD 6.8 9.4 12.0 10.8 ~
25

L0 7.3 8.5 10.0 10.8 ~

SD 5.9 7.4 8.7 9.0 -
30

L0 4.3 ~ ~ ~ 3.4

SD 3.9 ~ ~ - 3.5
Day Temperature *** V

Linear ***

Quadratic n.s.

54

Table 4 ~ continued

 

Cubic n.s.
Night Temperature ***
Linear ***
Quadratic n.s.
Cubic n.s.
Photoperiod ***
1 Missing treatment mean. Numerals represent treatment means from

1989 experiment.
V Significance of both 1988 and 1989 experiments combined at P = .001

(***), not significant (n.s.).

55

Table 5. Regression coefficients calculated to predict single leaf area
(of Emem§;e_z_axegige ‘Dollar Princess' plants from experiments conducted
during 1988 and 1989 studying the effect of DT, NT, and photoperiod on
[memeie morphology. Comparison of slopes and intercepts were evaluated

using the technique outlined by Snedicor and Cochran (1967).

 

 

 

 

 

 

 

Raw Data
SD LD Normalized Data Regression

Coefficients 88 89 88 89 SD LD
bo 12.95 10.39 14.54 12.68 13.10 14.99
b1 0.48 0.33 0.58 0.42 0.40 0.52
r2 0.62 0.75 0.76 0.80 0.66 0.81
Comparison Of Slopes

Raw data 88 SD versus 89 SD F = 3.6 (dfsl,31) n.s.

Raw data 88 LD versus 89 LD F s 2.7 (df=l,30) n.s.

Normalized data SD versus LD F 8 121.5 (df 8 1,61) ***

Comparison Of Intercepts
Raw data 88 SD versus 89 SD F = 20.9 (df=1,31 ) ***
Raw data 88 LD versus 89 LD F = 6.6 (dfsl,30) ***

Normalized data SD versus LD F a 12.43 (df - 1,61) ***

 

56
Table 6. The effect of DT, NT and photoperiod on W ‘Dollar
Princess' branch number at anthesis. LD were delivered as a 9~hr
photoperiod plus a 4~hr night interruption delivered using incandescent
lamps. SD were delivered as a 9~hr photoperiod only. A branch was

defined as any axillary break which has 2 or more nodes.

DT (°C) Treatment

 

 

NT (°C) _--
Treatment 12 16 20 24

12

LD 11.5 1 9.0 8.0 6.8

SD 12.8 10.3 10.2 8.0
16

L0 8.8 7.2 6.2 6.0

SD 9.0 9.2 9.2 7.0
20

LD 900 8.3 6.2 507

SD 7.8 6.0 6.6 5.8
24

L0 6.2 5.8 6.0 4.5

SD 5.8 7.8 7.2 6.6
Day Temperature *** V
Night Temperature ***
Photoperiod n.s.

 

1 Numerals represent treatment means from 1989 experiment.

57

Table 6 ~ continued

V Significance of both 1988 and 1989 experiments combined at P = .001

(***), not significant (n.s.).

58

Figure 1. The effect of the difference between DT and NT (DT
~ NT) on ﬁneneie_x_hymmige ‘Dollar Princess' internode
length on plants grown during the 1989 experiment.
Plants were grown under long day conditions, i.e. a 9~hr
photoperiod plus a 4~hr night interruption using

incandescent lighting at an irradiance of 2 molm’2 s”.

59

24/12

I

DOIII 84’"

I‘ll! 80H. IOIIO

[II

12112 l6/IG 20/20 24/24

1 f

A I I

lI/IC IIIIO SOII4

”ISO “[84

12/24

FUCHSIA HYBRIDA ~ LD

 

60

Figure 2. The effect of the difference between DT and NT (DT~
NT) on Wide ‘Dollar Princess' internode
length on plants grown under LD (9~hr photoperiod plus 4-
hour night interruption using incandescent lamps at an
irradiance of 2 umol m“2 s") and SD (9~hr photoperiod) .
Data were normalized across 1988 and 1989 experiments
within photoperiod treatments. The regression function
calculated from LD data was Internode Length (cm) =
4.727 + (0.129 * X) (r2 = 0.87). The regression
calculated from SD data was Internode Length (cm) =

1.871 + (0.071 * X) (r?- = 0.64).

Aoov otneotoQEoH EEZ oc< >00 coofom mocototE

ON

 

Erwin - 28

61

 

 

 

mF OF m 0 ml or... m?! ON... mm...
>\b _ _ _ L _ _ _ my
I
IN
In
I
r...»
o 00 Gwen“
be... 1..
O O®Q 0
WV 0
\ coamotomm xoo tozm II lo
0 c
\ O 9602 >00 form I
O co_mmoumom >00 95.. l 1m.
O 9.602 .80 0:3 .0

 

(0.13) 01609“) epoweiu)

62

Figure 3. The effect of the difference between DT and NT and
photoperiod on Fuchsia x hybriea ‘Dollar Princess' leaf
area on plants grown under LD (9~hr photoperiod plus 4~hr
night interruption using incandescent lamps at an
irradiance of 2 umol m'2 s") and SD (9~hr photoperiod) .
Data were normalized across time within each photoperiod.
The regression function calculated from LD data was Leaf
area (cmz) = 14.99 + (0.52 * X) (r2 = 0.81). The
regression function calculated from SD data was Leaf

area (cmz) = 13.10 + (0.40 * X) (r2 = 0.66).

Erwin - 30

63

AOL 00300000000. EEZ 93 >00 00020.00 00000030

ON

m:
_

O_P m

_

ml. or... mwl ONI
L _

 

 

 

_ m
T
[OP
10F
T
006000000 >00 tocm ll ION
0:002 >00 tozm s
0230.600 >00 90.. ..
0:002 >00 90.. o .

 

 

(,-)oa| zL110) new 108')

64

Figure 4. The effect of ADT and photoperiod on Fuehsia x
nymmige ‘Dollar Princess' branch number at anthesis on
plants grown under LD (9~hr photoperiod plus 4~hr night
interruption using incandescent lamps at an irradiance of
2 umol s’1 m Q) or after 78 days on plants grown under SD
(9~hr photoperiod). Only data from the 1988 experiment
is presented. The regression function calculated from
the data is the exponential function Branch Number =

106.28 * EXP(~.22188 * X) + 5.43 (r2 = 0.74).

Erwin - 32

65

ON

Gov 0030000E0e >200 0000024

 

 

em mm om me on 4: Ne
_ _ _ _ _ _ _ . _

mc00§ 0.. o 0

O mcooE 0m I I

cozocsm 0280.500 II

If! on I I

{OIIIIIOO O I O O
I III/ 0
I I /// O -
I //
/ I o rm
0 ///
/
/ r
0| I D / o
//
I I/ 10—
/
// -
0

IN—

. .I

 

 

JequmN 0300,18 0183,01

66

Section IV.

Differential Sensitivity Of Plant Stem

Elongation To Temperature Fluctuations During The Day

67

Differential Sensitivity Of Plant Stem

Elongation To Temperature Fluctuations During The Day
3. E 1 a d o D. ins

Department Of Horticulture
Michigan state University
East Lansing, Michigan 48824, U.8.A.

Keywords: temperature, thermomorphogenesis, circadian rhythm,

stem elongation, thermoperiodism.

Received for publication . Mich.

 

A91? - Expt. Sta. No. . The authors

 

W011101 like to express their appreciation to Brian J. Kovanda
£631? technical assistance, and to Andy Mast Greenhouses Inc.
and Four Star Greenhouses for donation of plant material. The
‘3c’531t of publishing this paper was defrayed in part by payment
of page charges. Under postal regulations, this paper must be

he3'i‘eby marked MW solely to indicate this fact.

Current address: Department of Horticultural Science,

The University of Minnesota, 1970 Folwell Ave, St. Paul,
Minnesota, 55108.

68

Abstract

Plant stem elongation is sensitive to temperature

fluctuations during the day. W cv Nellie

White. WW cv Red Hot Sally. and 112201218115
We cv Blush were grown at constant 20 C. Each of the

above plant species received either a 15 C or 25 C temperature
pulse at different times and for varying durations during the
day or the beginning or end of the night period. m
internode length was significantly reduced when plants
received a 15 C pulse during the first 2 or 4 hr of the light
period. LL11,” internode length was also significantly
reduced if plants received a 25 C pulse during the last 2 hr
of the dark period. Imeatieme and m internode lengths
were not significantly reduced by a cool temperature pulse
dur ing the day. However, 1mm and 531113 internode
elongation increased if plants received a warm temperature
Pulse during the day. Specifically, the earlier during the
day that plants received a warm temperature pulse, the greater

the stimulation of stem elongation.

69
Introduction

Research by Went (1944) showed that day (DT) and night
temperature (NT) had different, but significant, effects on
plant stem elongation. Specifically, stem elongation
increased as DT increased and NT decreased. In contrast, Dale
( 1964) showed that We stem elongation was
optimal when DT and NT were constant. Research by Smith and
Langhans (1962) and Roh and Wilkins (1973) showed that stem
elongation of WW increased only when DT

exceeded 21°C.
Recent research supports the conclusions of Went. Tageras
( 1 9 79) showed that W stem elongation increased
as 01‘ increased and NT decreased. Karlsson et. al. (1989) and

Berghage et. a1. (1989) showed that DT and NT had similar

effects on plant stem elongation of 200W

(Chrysanthemum) and Wm (poinsettia) . as
those seen by Tageras (1979) and Went (1944) .

More recent research suggests that stem elongation may be
inf luenced more by the relationship between DT and NT rather
than absolute DT and/or NT within a limited temperature range.
Research by Lecharny and Wagner (1985) suggested that
W stem elongation rate responded to the relationship
baht-teen DT and NT. The significance of the relationship
bet‘ween DT and NT was confirmed by Erwin et a1. (1989) on

W. Stem elongation increased as the

difference (DIF) between DT and NT (DT-NT) increased, i.e. as

7O

DT increased relative to NT. Similar effects of DIF were

found on We, MW. We
0221115, M129, Measles; (Erwin. personal
observation), WW (Karlsson et. al.,
1989), W (Berghage et al., 1989), and
gemmemgle_ieepbylle (Moe, personal communication).

In addition to DIF, average daily temperature (ADT) was
also important in Euphorbia (Berghage 1989), and QQQQEQBEQQEQ

(Karlsson et al., 1989). An ADT effect on stem elongation
was, however, not evident. in ,Emebe1e_ or :Lilimm, (Erwin,
personal observation; Erwin et al., 1989a).

The effect of temperature on plant stem elongation is not
uniform during a day or night thermoperiod. This was not
unexpected since plant stem elongation is not uniform during
a 24 hr period but follows a circadian rhythm (Went, 1944;
Lecharny and Wagner, 1985; Erwin and Heins, 1988). Plant
stem elongation is greater during the night than the day
(Went, 1944; Erwin and Heins, 1988). Lecharny and Wagner
(1985) showed that cool temperature pulses during the night
period could rephase the circadian stem elongation rhythm.
Preliminary research by Erwin et al. (1989) suggested that a
cool pulse (~DIF) in temperature during the early part of the
morning was more effective in inhibiting stem elongation than
a cool pulse in the afternoon on Lilium.

The objective of the study presented in this paper was to

determine the effects of temperature fluctuations during the

71
day on plant stem elongation. The effects of warm and cool
temperature pulses immediately before and after the

photoperiod were also evaluated.

Materials And Methods

Wu CW ‘Nellie White'. Impatiens
Mariana cv ‘Blush' . and We cv ‘Red Hot Sally'
were studied in this experiment. , Vernalized Lilium

memgiﬁiemmm plants in 15.2 cm.plastic pots with-a soil volume
of 2,570 cm3 were obtained after flower initiation, i.e.
approximately 40 days after emergence. All remaining plant
species were obtained as 10~day~old seedlings. All seedlings
were transplanted 7 days before the initiation of the
experiment into plastic containers composed of 6 individual
cells per container with a medium volume of 50 cm’ per cell 7
days before the initiation of the experiment. All plants were
maintained in a glasshouse maintained at 20 C prior to the
initiation of experimental treatments. Mean day and night
temperatures did not vary by more than 2 C.

Plants were then placed in glasshouses maintained at 15,
20, or 25 C on 8, April, 1989. Average temperatures within
the glasshouse sections did not vary by more than 2 C during
a 24 hr period. Plants were moved from the 20 C glasshouse
into either the 15 or 25 C glasshouses at different times and

for different durations as shown below:

72
Experimental Treatments
0700-0900 hr
0900-1100 hr
1100-1300 hr
1300-1500 hr
1500-1700 hr
1700-1900 hr
0900-1300 hr
1300-1700 hr
constant 20°C

Transfer of plants among treatments required 10 min. An
opaque curtain was pulled over the plants at 1710 hr after
they were moved and was retracted at 0900 to provide an 8 hr
10 min photoperioda 'The uppermost leaf pair on each.plant was
marked with a black ink dot to identify the developmental
stage when each plant was first exposed to experimental
treatments.

Greenhouse temperatures were controlled using a
greenhouse climate control computer and monitored by a
datalogger using iron/constantan thermocouples. Temperatures
in each greenhouse section and light intensity were measured
every 10 sec by the datalogger and were averaged to provide
mean temperatures every 2 hr. All plants were within 2 m of
temperatures sensors during the experiment.

Internode length was measured on the second internode
above the marked leaf pair on Selgie and meeﬁieme after 30
days. Internode length data on mem were collected at
anthesis. Lilimm internode length was calculated by dividing

the increase in stem length from. the beginning of the

experiment by the number of stem leaves which had unfolded

73

above the marked leaf.

Results And Discussion

The sensitivity of Lilium stem elongation to temperature
fluctuations varied during the day (Figure 1) . A cool
temperature pulse (from 20 to 15 C) during the first 2 hr of
the morning significantly reduced internode length from..27 to
.20 cm. In addition, a 4 hr drop in temperature during the
morning or the afternoon also significantly reduced internode
length in Mm (Figure 1) . There was no significant
difference in internode lengths of plants which had received
cool temperatures from , 0900-1100, 0900-1300, and 1300-1700
hr and plants which received cool temperatures from 0900-1700
hr, i.e. all day.

The sensitivity of Selgie__emlengene and Imeetiene
melmemieme stem elongation to a cool temperature pulse was
similar to that seen in Lilimm (Tables 1 and 2), i.e. stem
elongation was reduced by cool temperatures early in the
morning. However, the variation in internode lengths was so
great that a significance between internode lengths from the
cool temperature treatments and the constant 20 C could not be
determined.

The sensitivity of a plant to a warm temperature pulse
also varied during the day (Figures 1 and 2). Lilium
internode length significantly increased.when plants received

a 4 hr increase in temperature from 20 to 25 C during the

74
morning or the afternoon (Figure 1) . For example, mm
internode length increased from .27 to .34 and .33 cm when
plants received a warm temperature pulse from 0900-1300 or
1300-1700 hr, respectively (Figure 1). In contrast, stem
elongation was significantly inhibited by a warm temperature
pulse during the last 2 hr of the night (Figure 1).

As with a cool temperature pulse £4,111; and Meme
internode lengths varied to such an extent that significance
of treatments was not determined using mean separation
techniques. However, a significant trend was determined using
linear regression analysis. Stimulation of stem elongation by
a warm temperature pulse decreased as the temperature pulse
occurred later during the day (Figure 2).

Interestingly, Imeeﬁieme internode length significantly
increased when plants received a warm temperature pulse during
the beginning' of the night. period. For ‘example, mean
internode length increased from 1.95 to 3.55 cm when plants

received a warm pulse from 1700-1900 hr (Table 3).

75

Literature Cited

Berghage, R.D. 1989. Modeling stem elongation in EQEQQIQIQ
meleberzime. PhD Thesis. Michigan State University.

Dale, J.E. 1964. Some effects of alternating temperature on
the growth of French bean plants. Amm, Bot“ N.S.

28(109):127~135.

Erwin, J.E., R.D. Heins, and M.G. Karlsson. 1989.

Thermomorphogenesis in W 511mm,.
76(1):47~52.

Erwin, .J.E. 1990. Thermomorphogenesis :hi plants. PhD

Thesis, Michigan State University.

Karlsson, M.G., R.D. Heins, J.E. Erwin, R.D. Berghage, W.H.
Carlson, and J .A. Biernbaum. 1989. Temperature and
photosynthetiijhoton flux influence chrysanthemum.shoot

development and flower initiation under short-day

conditions. 11.8merl_§221_ﬂortl_§sil 114(1)=158-l63-
Lecharny, A., M. Schwall, and E. Wagner. 1985. Stem

elongation rate in light grown plants. 21em§e_£nyeielm,
79:625-629.

76
Roh, S.M., and H.F. Wilkins. 1973. Influence of temperature
on the development of flower buds from the visible bud

stage to anthesis of Lilium lomgiﬁlommm Thunb. cv. Ace.
Hortscience, 8:129-130.

Smith, D., and R. Langhans. 1962. The influence of day and
night temperatures on the growth and flowering of the

Easter lily (W Thunb. var ‘Croft').
Amer. Soc. Hort. Sci., 80:593-598.

Tageras, H. 1979. Modifying effects of ancymidol and
gibberellins on temperature induced elongation in W
£_h¥2£iddo Acta Hort. 91:411-417.

Went, F. W. 1957. The experimental control of plant growth.
Chr. Bot. 17. The Ronald Press Co., N.Y., N.Y., pp. 223-

226.

Went, F.W. 1952. The effect of temperature on plant growth.

MW. 4:347-362.

77

Table 1.

at different times of the day on geiyie_§21engem§ cv Red

Hot Sally internode length (cm).

at 20°C .

prescribed times.

and was terminated at 1700 hr.

The effect.of warm.and cool temperature fluctuations

All plants were grown
Plants were moved to either 25°C or 15°C at the

The photoperiod was initiated at 0900

 

Time Of Exposure 15°C
0700 to 0900 hr 2.17 i
0900 to 1100 hr 1.72 i
1100 to 1300 hr 1.67 i
1300 to 1500 hr 2.30 i
1500 to 1700 hr 1.95 i
1700 to 1900 hr 1.52 i
0900 to 1300 hr 1.43 i
1300 to 1700 hr 1.80 i
constant 20 2.10 i
0900 to 1700 hr 1.30 i

Numerals represent treatment

deviation about the mean.

|+

|+

|+

|+

|+

0.16

0.29

means and the standard

78

Table 2. 'The effect of warm.and cool temperature fluctuations
at different times of the day on lmme;ieme_zelle;ieme cv

Blush internode length (cm).

20°C.

prescribed times.

All plants were grown at

and was terminated at 1700 hr.

Plants were moved to either 25°C or 15°C at the

The photoperiod was initiated at 0900

 

1100
1300
1500

1700

0900

1300

Of Exposure

to
to
to
to
to

to

to

to

0900

1100

1300

1500

1700

1900

1300

1700

constant 20

0900 to 1700

hr
hr
hr
hr
hr
hr

hr

hr

hr

deviation about the mean.

|+ H- Ft I+

|+

|+

I+

l+

|+

Numerals represent treatment

|+ H- Pt I+

|+

I+

|+

|+

0.66

0.09

0.29

0.66

means and the standard

79

Figure 1. The effect of the time and duration of a cool or
warm temperature exposure on W cv Nellie
White internode length. Plants were grown at constant 20
C accept when plants received the cool temperature pulse
(15 C). The photoperiod was initiated at 0900 and was
terminated at 1700 hr. Significance between treatment
means was determined using Tukey's test for mean
separation (H.S.D.). Treatment means which are above or
below the lines are significantly different from plants

grown at constant 20 C.

80

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81

Figure 2. The effect of the time and duration of a warm

temperature exposure on W and Diseases
W internode length. Plants were grown at

constant 20 C except when plants received the warm
temperature pulse (25 C). The photoperiod was initiated

at 0900 and was terminated at 1700 hr.

82

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83

Section V.

Interaction Between Light Quality,
Day/Night Temperature Environment And

Temperature EnvironmentGrowth Regulators

on W stem Elongation

84
Interaction Between Light Quality, Day/Night Temperature

Environment, And Growth Regulators
0n Eushsia_x_hxbrida stem Elongation

gene 3. eggiml egg 39151 e, Heine

DepartIent Of Horticulture
Michigan State University

East Lansing, Michigan 48824 U.8.A.

Keywords: thermomorphogenesis , phytochrome , thermoperiod ,

gibberellin, ancymidol.

Received for publication . Mich.
Agr. Expt. Sta. No. . The authors
express their appreciation to Brian J. Kovanda for technical
assistance, and to Mid-American Growers for donation of plant
material. The cost of publishing this paper was defrayed in
part by payment of page charges. Under postal regulations,

this paper must be hereby marked W solely to
indicate this fact.

1 Current address: The Department Of Horticultural Science,

The University Of Minnesota, 1970 Folwell Ave., St. Paul, MN
55108

85
Abstract

The effect of light quality, day\night temperature
environment, and growth regulators on {memeie_x_mymmiee cv
‘Dollar Princess' stem elongation was studied. Ememeie stem
elongation was influenced by the relationship between day and
night temperature. Internode length increased as the
difference (DIF) between day (DT) and night (NT) temperature
(DT-NT) increased. Red lighting during the night period had
no significant effect on stem elongation. Far red lighting
during the night period increased Fuchsie stem elongation.
Light quality interacted with DIF to affect stem elongation.
The percentage increase in stem elongation from an expsoure to
far red lighting during the night period decreased as DIF
increased. The percentage increase in stem elongation from an
application of 5A00 decreased as DIF increased. In contrast,
the percentage inhibition of stem elongation from an
application of a gibberellin biosynthesis inhibitor
(ancymidol) increased as DIF increased. The interaction
between light quality, DIF and growth regulators suggests that
light quality and DIF may elicit responses through affecting

the concentration of endogenous gibberellins.

86
Introduction

Plant stem elongation is influenced by light quality
(Jabben and Holmes, 1983) and temperature (Went, 1952). Stem
elongation increases when plants are exposed to light high in
the far red (FR) portion of the light spectra (Vince-Prue,
1977). The extent to which FR stimulates stem elongation
decreases as the time of an exposure occurs later in the
scotoperiod (Vince-Prue, 1977; Wilkins, 1985). Compared to
FR, blue or R lighting typically reduces stem elongation when
an exposure occurs during the scotoperiod (Jabben and Holmes,
1983). However, R has been shown to increase stem elongation
in some species when given late in the scotoperiod with
Qemdramememe (Cathey, 1974) or continuously in Fuchsie (Vince-
Prue, 1977).

Stimulation of stem elongation in Qnememegimlpmm by FR
during the scotoperiod is reversible by a subsequent exposure
of a plant to R. In contrast, inhibition of stem elongation
by R, compared to stem elongation in the dark only, is
reversible by a subsequent exposure of plants to FR (Morgan
and Smith, 1981; Vince-Prue, 1977). Photoreversability of a
stem elongation response to R and FR is regarded as evidence
for the involvement.of phytochrome (Stolwijk, 1954; Downs et.
al., 1957). R converts Pr to P". FR converts Pfr to Pr
(Borthwick et. al., 1952). Phytochrome in the Pfr form
restricts stem elongation whereas phytochrome in the P} form

allows maximal elongation (Morgan and Smith, 1981; Smith and

87
Morgan, 1983).

Recent evidence suggests that morphological changes in
plant growth which are typically ascribed as phytochrome
mediated can be induced by temperature alone, i.e. plant
growth is thermomorphogenic (Erwin et. al., 1989). In
particular, Demgmejememe (Karlsson et al, 1989), Lﬂigm (Erwin

et al., 1989), Sid—111930.01; (Moe et al., 1990), and We
(Berghage et al, 1990) , stem elongation is strongly dependent

on the relationship between day and night temperature (DIF =
day temperature - night temperature). Stem elongation
increased as DIF increased, i.e. as day temperature increased
relative to night temperature.

Light quality and DIF interact to affect plant stem
elongation. DIF only affected We stem
elongation if plants received R or darkness during the
scotoperiod (Moe et. al., 1990). Irradiation of plants with
FR during the scotoperiod eliminated the response of stem
elongation to DIF.

Evidence exists which suggests similar transduction
pathways for both. photomorphogenic and thermomorphogenic
responses. The transduction pathway for light effects on
plant stem elongation are unclear but suggest the involvement
of gibberellins (Loveys and Wareing, 1971a and b). Recently,
Erwin et a1. (1989) and Moe et al. (1990) suggested that
promotion of stem elongation by DIF was also mediated by

gibberellins.

88
The objective of the current study was to determine
whether thermomorphogenic and photomorphogenic effects on stem
elongation act through similar or different causal pathways.
The interaction between DIF, light quality and exogenous
applications of both GA,”7 and ancymidol was studied to this

end.

Materials And Methods

Rooted cuttings of Fucmsie m hybride cv Dollar Princess
were planted in 12.5 cm plastic pots in a soilless medium
consisting of equal parts of sphagnum peat, perlite, and
vermiculite on 6 April, 1989. Plants were then placed in a
controlled environment glasshouse under natural photoperiod
conditions maintained at 20 i 2 C. The photoperiod was ca. 9
hr 15 min. in length which maintained plants in a vegetative
state. After 2 wks plants with 5 nodes were selected and the
uppermost leaf pair on each plant was marked with black ink.
All plants were then moved into controlled environment
chambers maintained at 24, 20, and 16 C. Mean temperatures
within the chambers did not vary by more than 1 C.

Plants received a 12-hr photoperiod with an intensity of
125 umol s"m'2 (13 mol day”) from 2000 to 0800 hr. Lighting
was delivered with high pressure sodium lamps and incandescent
lamps. Irradiance delivered with incandescent lamps was 25%
of the total wattage delivered with high pressure sodium

lamps. The light spectra which plants received during the

"‘1

89

photoperiod is shown in Figure 1a. The R/FR ratio of the
artifical lamps versus day light were 2.77 and 1.32,
respectively. R/FR ratio determinations were made using an
Isco spectroradiometer.

Each chamber was divided into 3 lighting sections during
the scotoperiod (0800 to 2000 hr): supplemental R,
supplemental FR, and darkness (D). R and FR were delivered
with fluorescent 'lamps developed by Sylvania to deliver

lighting high in R and FR. The lights delivered an irradiance

1 ~2

of 5 umoles s' m at the top of the canopy. A filter was
necessary to remove blue light from the FR source. The R/FR
ratio of the red and far red lamps was 80 and .05,
respectively. The spectra for the R and FR light sources are
shown in Figure 1a. Light pollution between sections was
eliminated by pulling an opaque plastic curtain between the
plants at 0810 and retracting it at 2000 hr.

Plants were moved among chambers to deliver the
temperature treatments and between lighting sources during the
night period to complete the treatment combinations for each
experiment shown in Table 1. Day/night (DT/NT) temperature
environments were 24/16 (+ DIF), 20/20 (0 DIF), and 16/24 C (-
DIF). Lighting treatments consisted of supplemental lighting
for 30 min at the beginning of the night (EOD), continuous
lighting (CONT), or darkness.

Exogenous applications of GA,”7 and a GA biosynthesis

inhibitor were applied to study the interaction of both DIF

90

and light quality on endogenous gibberellin concentration.
GA,”7 ‘was applied as five 20 ul droplets of a 10 ppm
concentration solution (1 ug GA“7 plant”) to the uppermost
leaf pair 5 days after the initiation of the experiment using
a digital Finnipippette (Cole-Palmer) . The GA synthesis
inhibitor ancymidol (alpha-cyclopropyl-alpha-(4-
methoxyphenyl)~5-pyrimidiemethanol) was applied as five 20 ul
droplets of a 50 ppm concentration solution (5 ug ancymidol
jplant”) to the uppermost leaf pair'5 days after the initiation
of the experiment. No plants received both GAMJ and
ancymidol.

Plants received temperature and lighting treatments for
21 days. At the termination of the experiment, data was
collected on internode length of the second internode above
the marked leaf pair. There were 4 replicates per treatment
within each temperature environment. Lighting treatments were

replicated twice over time.

Results
Emeneme_x_hymzige cv Dollar Princess internode length
increased from 3.2 to 4.4 cm as the difference (DIF) between
day (DT) and night (NT) temperature (DT-NT) increased from -8
to +8 C when plants received no lighting during the night
period.
The increase in internode length as DIF increased from a

0 to a +8 DIF was not as great as was expected based on

91

previous research (Erwin, 1989). In some cases internode
length was greater when plants were grown with a 0 DIF than a
+8 DIF (Table 2). This was unexpected as internode length in
Emeneie was clearly shown to increase linearly as DIF
increased.within this temperature range when plants are grown
under sunlight (Erwin, 1989). The greater stem elongation in
the 20 DT/20 NT (0 C DIF) treatment may be attributed to less
movement of plants than in the 24/16 C or 16/24 C
environments. Movement of plants could potentially decrease
stem elongation, i.e. stem elongation is thigmomorphogenic
(Wareing, 1981). Plants in both the ~DIF and +DIF
environments were moved a minimum of 2 times every 24 hr.
Plants in the 0 DIF environment were not moved among chambers
but were only moved within a chamber. All plants within the
0 DIF environment were agitated at 0800 and 2000 hr to
simulate diurnal movement in an effort to reduce potential
thigmomorphogenic effects on stem elongation, however, the
movement may not have been as vigorous as that which plants
moved among chambers received. Due to the potential
thigmomorphogenic effects on stem elongation, results were
normalized by dividing internode lengths by the internode
length of control plants within temperature and lighting
environments for further data analysis (Figures 2, 3, and 4).

Light quality affected internode length in different
ways. R did not affect internode length. In contrast, FR

lighting given as an end-of-day (EOD) treatment or as

92
continuous irradiation (CONT) during the night period
increased internode length (Table 2, Figure 2). Continuous FR
resulted in greater elongation than an EOD FR exposure.

The question arises as to whether light quality and DIF
interact to affect Eggheie stem elongation. To analyze the
simultaneous action of light quality and DIF on stem
elongation, criteria developed by Lockhart (1965) were
employed. If 2 factors act independently on the same causal
sequence to elicit a response then a multiplicative behavior
will be evident between those factors, a synergism may be
apparent as the response to factor 1 will depend on the level
of factor 2. In contrast if 2 factors act independently via
different casual sequences to elicit a response then an
additive behavior will be evident between those factors.

Clearly the temperature environment which plants were
grown under had a significant impact on the response of
‘Ememeie stem elongation to lighting treatments. The effect
of a lighting treatment on Ememeie stem elongation decreased
as DIF increased (Figure 2) . Therefore, light quality and DIF
did not act independently to control stem elongation in
Maia-

Moe et. a1. (1990) also found an interaction between DIF
and light quality on gempenmle_jeeenylle where only plants
which received R or darkness during the night period responded
to DIF. Irradiation.of plants with FR.eliminated.the response

of plant stem elongation to DIF. Therefore, Moe et al

93

suggested that phytochrome must be in the Pfr form for plant
stem elongation to respond to DIF. Eucmsia stem elongation
in this experiment responded to DIF after irradiation with
either R or FR lighting (Table 2, Figure 2). Therefore, the
necessity of phytochrome being present in the P",state as Moe
et al. (1990) suggested was not apparent on Fmemeie in this
experiment.

Application of GA,“7 increased stem elongation in all
temperature environments and lighting treatments (Table 2,
Figure 3) . Percent increase in internode elongation resulting
from an application of GA6+7 decreased as DIF increased (Figure
3). For example, as DIF increased from -DIF to + DIF when
plants were not irradiated.with light during the scotoperiod,
stimulation of internode elongation by GA“, decreased from 133
to 89% (Figure 3).

Application of ancymidol to plants resulted in inhibition
of internode elongation in plants which received no lighting
during the scotoperiod or EOD R lighting (Table 1, Figure 4);
The greatest inhibition of internode elongation occurred when
plants received no lighting. Inhibition of internode
elongation by ancymidol increased from 0 to 41% as DIF
increased from a -DIF to a +DIF when plants received no
lighting treatment during the scotoperiod (Figure 4).
Interestingly, no inhibition of elongation was evident in the
continuous FR treatment (Figure 4). Evidently, continuous FR

lighting was able to overcome any inhibition of GA

94

biosynthesis which resulted from the ancymidol application.

The transduction pathways for phytochrome and temperature
effects on plant stem elongation are unclear. Morgan and
Smith (1983) showed that inhibition of Eneeeelme stem
elongation by R or white light was overcome by an exogenous
application of GA3. R followed by FR negated the G15.3 effect,
i.e. light quality and GA3 affected stem elongation in a
multiplicative fashion. Similarly, Reid et. al. (1968 a and
b) demonstrated that an exposure of etiolated leaves of
He;§emm_ymlgeme to R led to a rapid increase in endogenous
gibberellin. Research by Loveys and Wareing (1971 a, b)
demonstrated that some but not all of the increase in
gibberellin following a R exposure was due to a release of
gibberellin from a bound form. In addition to gibberellin,
phytochrome has been shown to induce cytokinin biosynthesis
(Wareing, 1981) and ethylene (Kang and Burg, 1973). The
interaction between light quality and GA suggested that these
2 factors may have a similar transduction pathway with respect
to stem elongation.

In contrast, data presented by Mohr (1972) suggested that
light quality and exogenous applications of GA3 acted in an
additive fashion on mustard hypocotyl lengthening. Based on
this information.Mohr (1972) concluded that light quality and
gibberellins act through different casual pathways to affect
plant stem elongation.

Recently, Erwin et. a1. (1989) and Moe et. a1. (1990)

95
suggested that promotion of stem elongation by temperature may
be mediated by GA. Inhibition of stem elongation by a

negative DIF environment was overcome by an exogenous

application of GA6+7 on W (Zieslin and

Tsujita, 1988) and gempemmle_ieeemylle (Moe et. al., 1990).
Little elongation resulted from an application of GA“, to
W grown in a +DIF environment.

Promotion of stem elongation by'a +DIF environment was
eliminated by an application of a GA biosynthesis inhibitor
(ancymidol). Ancymidol had little or no effect on stem
elongation of plants grown under a -DIF environment (Erwin et
al., 1989). The question arises as to whether DIF and
phytochrome interact to mediate GA synthesis and/or the
response of plant tissues to GA?

Results shown in the current experiment suggested that
DIF, light quality, and gibberellins may act through similar
causal pathways. Percent promotion of Mi; internode
elongation which received R or GA“, alone was significantly
less than that of plants which received R plus GA‘"7 (Table 2,
Figure 5) . The apparent synergism between R and GA“, on
Emeheie internode elongation suggested that this response was
multilicative in nature and not additive (Lockhart, 1965) .
These data suggest that DIF and light quality may interact to
affect Emcheie stem elongation through the same casual

sequence which involve gibberellin.

96

Literature Cited

Berghage, R.D. 1989. Temperature effects on poinsettia stem

elongation. PhD Thesis. Michigan State University.

Borthwick, H.A., S.B. Hendricks, M.W; Parker, E.H; Toole, V.K.

Toole. 1952. A reversible photoreaction controlling

seed germination. Emoe. Negl, Aeed. Sci,, U.S.A.,
38:662-666.

Cathey, H.M. , 1974. Participation of phytochrome in regulating

internode elongation of WW (Ramat-)
Hemsl. Jl_Amerl_§921_ﬂortl_§sil. 99(1)=17-23-
Downs, R.J., S.B. Hendricks, H.A. Borthwick. 1957.

Photoreversible control of elongation in Pinto beans

and other plants under normal conditions of 911th.

52L;_§§1;1 118:199-208.

Erwin, J .E. 1989. Thermomorphogenesis. PhD Thesis. Michigan

State University.

Erwin, J.E., RJD. Heins and M.G. Karlsson. 1989.

Thermomorphogenesis in Lilimm_1engi§le;mm. Amer, e.
2221. 76(1):47-52.

97
Jabben, M., and M.G. Holmes. 1983. Phytochrome in light
grown plants. in Encyclopedia Of Plant Physiology. vol
168 d. W. Shropshire and H. Mohr. Springer-Verlag Pub.,

N.Y., New York. pp. 704-722.

Kang, B.G., and S.P. Burg. 1973. Role of ethylene in
phytochrome-induced anthocyanin synthesis. Elemee,

110:227-235.

Karlsson, M.G., R.D. Heins, J.E. Erwin, R.D. Bergahge, W.H.
Carlson, and J .A. Biernbaum. 1989. Temperature and
photosynthetic photon flux influence Chrysanthemum shoot

development and flower initiation under short-day

conditions. WM... 114:158-163.

Lockhart, J .A. 1965. The analysis of interactions of physical
and chemical factors on plant growth. Amme_3eye_£1en§

210019.11. 16:37.

Loveys, B.R. and P.F. Wareing. 1971a. The red light
controlled production of gibberellin in etiolated wheat

leaves. ElemEe, 98:109-116.

Loveys, B.R., and P.F. Wareing. 1971b. The hormonal control

of wheat leaf unrolling. EleQEe, 98:117-127.

Moe,

98

R., R.D. Heins and J.E. Erwin. 1989. Stem elongation

and flowering of the long day plant Campanmle isoemylle

Moretti. is response to day and night temperature
alterations and light quality. Physiol. Plans}. (in

review).

Morgan, D.C., H. Smith. 1981. Non-photosynthetic responses

Mohr,

Reid,

to light quality. In: Encyclopedia of plant physiology,
N.S. vol. 12A; Physiological plant ecology I. Ed. O.L.
Lange, P.S. Nobel, C.B. Osmond, H. Ziegler. Springer,

N.Y., New York. pp. 109-130.

H. 1972. Lectures on photomorphogenesis. Springer-

Verlag, New York, N.Y., pp 88-90.

D.M., and J.B. Clements. 1968a. RNA and protein
synthesis: prerequisites of red light induced

gibberellin synthesis. Nat re, 219:607-609.

Reid, D.M., J.B. Clements, and D.J. Carr. 1968b. Red light

induction of gibberellin synthesis in leaves. EQLBIQ.

217:580-582.

99
Smith, H., D.C. Morgan. 1983. The function of phytochrome in
nature. In: Encyclopedia of plant physiology, N.S. vol.
16B: Photomorphogenesis, Ed. H. Mohr, W. Shropshire Jr.

eds. Springer, N.Y., New York. pp.409-517.

Stolwijk, J.A.J. 1954. Wavelength dependence of
photomorphogenesis in plants. Meded. Landbouwhogesch.

Wageningen, 54:181-244.

Vince-Prue, D. 1977. Photocontrol of stem elongation in

light grown plants of Wide. Planta. 133:149-

156.

Wareing, P.F., and I.D.J. Phillips. 1981. Growth and
differentiation in plants. 3rd Ed. Pergamon Press, New

York, N.Y., pp. 211-212.

Went, F.W. 1952. The effect of temperature on plant growth.

WM 4:347-362.

Wilkins, H. 1985. w in CRC Handbook Of
Flowering, vol. III., ed. H.A. Halevy, CRC Press Inc.,

Boca Raton FL, pp. 38-41.

100
Zieslin, N., and M.J. Tsujita. 1988. Regulation of stem
elongation of lilies by temperature and the effect of

gibberellin. Seienteia Hort. 37:165-169.

101
Table 1. Experimental treatments designed to study the
interaction between light quality and day/night
temperature environments on Ememeie_x_nym;ige cv Dollar
Princess internode elongation. Plants were moved among
chambers to deliver the temperature treatments and
between lighting sources during the night period to
complete the treatment combinations. Lighting treatments
consisted of supplemental lighting from red (R) or far
red (FR) light sources for 30 minutes at the beginning of
the night (EOD), continuous lighting (CONT), or darkness
(DARK) during the scotoperiod. GA“7 was applied as five
20 ul droplets of a 10 ppm concentration solution to the
uppermost leaf pair 5 days after the initiation of the
experiment using a digital Finnipippette (Cole-Palmer).
Ancyimidol was applied as five 20 ul droplets of a 50 ppm
concentration solution to the uppermost leaf pair 5 days

after the initiation of the experiment.

 

Day/Night Temperature Environment.(°C)

Lighting 24/16 20/20 16/24
Treatment (+DIF) (0 DIF) (- DIF)
DARK X x X

EOD R X X X

102

Table 1 ~ continued

BOD FR X X X.
CONT R X X X
CONT FR X X X
DARK + GA“, X X X
EOD R + GA," X X X
CONT R + GAW X X X
DARK + ancymidol X X X
EOD FR + ancymidol X X X

CONT FR + ancymidol X X x

103

Table 2. The effect of temperature, light quality, and growth

regulators on new cv ‘Dollar Princess'

internode length. Temperature environments were 24 day
(DT) temperature/16 night (NT) temperature (+ DIF), 20
DT/20 NT (0 DIF), and 16 DT/24 NT (- DIF). Lighting
treatments were for 30 minutes at the end of the day
(EOD), continuously (CONT), or not at all during the
scotoperiod (DARK). Light sources were either red (R) or
far red (FR). Growth regulator applications of five 20
ul droplets of either a 10 ppm solution (1 ug plant”) of
GA“7 (GA) or five 20 ul droplets of a 50 ppm solution (5
ug plant”) alpha-cyclopropyl-alpha-(4-methoxyphenyl)-5-
pyrimidiemethanol (anc) were applied 5 days after the

initiation of temperature and lighting treatments.

 

Temperature Environment

Lighting ---------------------------------------------
Treatment - DIF 0 DIF + DIF
EOD R 3.3 i 0.4 ‘ 4.2 i 0.4 4.1 i 0.5
EOD R+GA 7.2 i 1.2 7.7 i 1.3 7.8 i 0.6
CONT R 3.6 i 0.9 4.8 i 0.3 4.4 i 0.5
CONT R+GA 8.4 i 0.5 8.5 i 1.1 8.3 i 0.4
EOD FR 4.3 i 0.4 5.3 i 0.4 4.7 + 0.1

104

Table 2 - continued

EOD FR+anc 3.8 i 0.3 4.5 i 0.6 3.7 i 0.4
CONT FR 4.7 i 0.5 6.4 i 0.9 5.6 i 0.9
CONT FR+anc 4.8 i 0.2 6.5 i 0.5 5.9 i 0.5
DARK 3.2 i 0.6 4.3 i 0.6 4.4 i 0.5
DARK+GA 4.6 i 0.4 6.2 i 0.1 5.5 i 0.6
DARK+anc 3.2 i 0.5 3.6 i 0.5 2.6 i 0.0
Light Quality *** Y

Temperature Environment ***

Light x Temperature ***

‘ Numerals represent treatment means and standard

deviation about the mean.

V Significance at P = 0.001 (***).

105

Figure 1a. Light spectra of daylight versus artificial
lighting composed of high pressure sodium and

incandescent lamps used in this experiment.

106

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107

Figure 1b. Light spectra of red and far red light sources
used to deliver supplemental lighting during the

scotoperiod.

108

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109

Figure 2. Percent stimulation of elongation of the second
internode of Ememsie m hybmige cv Dollar Princess when

grown under different day/night temperature environments
and light quality treatments. Light quality treatments
were applied during the scotoperiod. Data is presented
as the percent stimulation as compared to plants which

received no lighting treatments.

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111

Figure 3. Percent stimulation of elongation of the second
internode of EBQD§1§__X__DYQLiQ§ cv Dollar Princess
following an application of GA“7 when grown under
different red lighting treatments. Red lighting
treatments were applied during the scotoperiod. Data is
presented as the percent stimulation compared to plants

which received the red lighting treatments or darkness

only.

112

 

 

 

 

 

 

 

 

 

 

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113

Figure 4. Percent inhibition of elongation of the second
internode of [Eggn§1a__z__nx§;igg cv Dollar Princess
following an application of ancymidol when grown under
different far red lighting treatments. Far red lighting
treatments were applied during the scotoperiod. Data is
presented as the percent inhibition compared to plants
which received the far red lighting treatments or

darkness only.

114

 

 

 

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115

Figure 5. Comparison of the increase in second internode
length resulting from red lighting only, application of

GA“7 only, or red lighting plus application of GAW on
Euchsia x hypridg cv Dollar Princess.

116

 

Lighting Only
GA Only

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117

Section VI.

A System For Measuring

Stem Elongation Kinetics

118
A System For Measuring

Stem Elongation Kinetics

by

Department Of Horticulture
Michigan state University

East Lansing, Michigan 48824 U.S.A.

Keywords: angular displacement transducer, linear

displacement transducer, circadian rhythm.

Received for publication . Mich. Agr.

Expt. Sta. No. . The cost of publishing this

 

paper was defrayed in part by the payment of page charges.

Under postal regulations, this paper must be hereby marked

agygztiggmgnt solely to indicate this fact.

1 Current address: The Department Of Horticultural Science,

The‘University'Of Minnesota, 1970 Folwell, St. Paul, MN 55108.

 

119
Abstract
A system was developed which utilizes angular
displacement transducers to measure short term changes in stem
elongation. The system has a resolution to 2 uM per 5 min
period. An internal standard was used to account for changes
in system output which result from changes in the temperature
and air movement in differing environments. Advantages of

this system are discussed.

120
Introduction

Methods for determining growth kinetics of plant stem
elongation.have been used since the early research of Sachs in
1874 (Penney et al., 1973; Sweeney, 1969). High resolution
measurement of the rate of stem elongation is useful in that
endogenous growth rhythms can be detected and studied more
closely. In addition, the kinetics of growth regulator action
and or other factors which affect stem elongation can be
elucidated. Studies of plant growth kinetics are, however,
often limited by the ability'of a system to resolve changes in
growth over relatively short periods of time (Penney et al.,
1973).

Early research by Went (1944) utilized a simple pulley
based system which was able to differentiate circadian rhythms
in W stem elongation. Later, time-lapse
photography was used to measure the rate of stem elongation of
Aygng coleoptiles (Ball and Dyke, 1954; Ball et al., 1957).
Verbelen et al. (1981) have used direct measurements of
hypocotyls to study circadian growth in Phasgolgs vulggzig.
Recently, methods for measuring growth rate based on changes
in continuous voltage output produced by transducers have been
developed.

A transducer is a differential capacitor with integral
voltage regulation, oscillator, demodulator, and output buffer
amplifier. A transducer is composed of a ferromagnetic core

which gives a differential inductance as its position changes

121

relative to coils fixed in the outer part of the unit. The
position of the shaft is converted into a direct current (DC)
voltage proportional in amplitude and polarity to the
displacement from the electrical null position of the
transducer. A diagram of an ADT is presented in Figure 1.
ADTs have traditionally been used for positioning optical
devices, rotary actuators, servo position feedback, and
robotic wrist and elbow control (Trans-tek).

Linear displacement transducers (LDT) have been used to
measure the stem elongation rates of Cucgmis (Addink and
Meijer, 1972), Eiggm (Warner and Leopold, 1971), yigng
(Lecharny and Jaques, 1982), Lygopgrsicum (Assaad Ibrahim et
al., 1981), and Chenopodium (Lecharny et al., 1985). In
addition, LDT have been used to study Maize (Hsiao et al.,
1970) and £93 (Christ, 1978) leaf expansion. Gordon and Dobra
(1972) developed a capacitance based system for growth
measurement . A system developed by Evans and Ray (1969) was
‘modified.by De La Fuente and.Leopold (1970) to utilize angular
displacement transducers (ADT) to increase resolution in
measurement of auxin stimulation of stem segment elongation.

This paper describes a system which utilizes ADT to
.measure stem elongation rates of intact plants. Benefits of
this system compared to previously developed growth.measuring

devices will be discussed.

System Composition

122

A simplified diagram of the system is shown in Figure 2.
A ‘Mylar' filament was tied to an elongating internode on one
end and a counterweight on the other. In between the plant
and the counterweight the filament was wrapped twice around a
pulley attached to an angular displacement transducer (ADT).
The ADT was held above a plant with a ring stand. The voltage
output from the ADT was used to measure stem elongation rate.
The ADT used was model 604-0001 produced by Trans-Tek Inc,
Ellington, Connecticut.

The transducer was powered by a :15 volt Dijower supply.
The range in voltage which is acceptable to power the
transducer is from 114.5 to :30 volts DC. The input voltage
is unregulated and is input polarity protected. The maximum
load when the current is less than iSmaDC is iZOmaDC. The
transducers are calibrated to deliver an output voltage of 100
mv DC per degree of rotation.

The monofilament between the pulley and the counterweight
was surrounded by a hollow plastic tube held in position by a
ring stand. The plastic tube reduced output ‘noise' which
resulted from swinging of the counterweight due to air
movement.

Output from the transducers was processed by an ‘Analog
Connection Jr. Board' (Strawberry Tree Computers, Sunnyvale,
California) which is an analog to digital (A/D) conversion
board. The board was mounted in a Zenith personal computer

and is connected to a terminal panel card which the

123
transducers are attached to. The terminal panels had cold
junction compensation to accommodate direct thermocouple hook-
up.

The complete system was composed of 8 transducers. Four
transducers were placed in each of 2 growth chambers. A
single A/D board and terminal panel is capable of having 8
independent transducers attached to it. However, only 4
terminals were used on a board for transducers. The other 4
terminals were utilized for measuring plant temperature, air
temperature, soil temperature, and irradiance in each growth
chamber. Therefore, 2 boards were required to run the 8
transducers which this system was composed of.

Software was provided with the A/D board which allowed
easy programming' of data conversion and logging. Each
transducer is calibrated independently to give accurate
conversion of voltage to a linear distance as each pulley had
a slightly’different.diameteru Input voltage*was converted to
millimeters prior to logging data onto a hard disk.

Data from all 16 inputs was collected every 3 s and was
placed in memory. After 5 min data from each terminal were
averaged and were written to a file on the hard disk. The
date and time is saved with the data.

Growth rate was determined by subtracting consecutive
measurements. Data were smoothed by using a moving average
technique (Penny et al., 1973; Lecharny and Wagner, 1984).

Discussion

124
W The output voltage from an ADT is sigmoidal in
nature. .A.plot of the output voltage versus shaft position is
shown in Figure 3. Because of the sigmoidal nature of the
output voltage as the shaft rotates, the output is
proportional to the position of the shaft only in certain
ranges. Shaft rotation which includes an increase in position
angle exceeding 90° will result in an output voltage which is
not proportional to the change in position of the shaft. The
typical linear range utilized is often 60° which ranges in
voltage from -3 to +3 volts DC (Figure 3). If the output
voltage exceeds +3 volts the shaft must be turned back to a
position within the linear range. A conversion factor was
calculated and utilized by the software to convert the output
voltage of the transducer within the linear range as shown

below:

Scale maximum - Scale minimum

Conversion factor = --------------------------------

6 volts

The scale maximum and minimum was equal to 1/6 th of the
diameter of the pulley, i.e. 60°«of rotation. Six volts was
the usable linear range of output voltage. With the system
described in this paper the usable range after conversion was
approximately 25 mm. In order for -3 volts to correspond to

0 mm an offset factor was calculated.

125

Offset factor = scale x (input minimum — scale minimum)

If the position of the transducer went below or above 0 to 25

mm, an audible alarm was activated.

Pulley Diameter; The resolution of an ADT system was
influenced by the diameter of the transducer shaft. The
system described utilizes a set of pulleys which increased the
diameter of the shaft and therefore the distance which the
shaft could rotate before the output voltage moved out of the
linear range. Experiments which involve rapid stem elongation
required larger pulleys as opposed to experiments which entail
slower rates of stem elongation which could utilize smaller
pulleys. The relationship between pulley diameter and usable
distance of the pulley is shown in Figure 4. Pulleys were
affixed to the transducer shaft using rubber cement. In this
way pulleys are firmly attached to the shaft but could be

removed easily.

Mgngfilamgnt_ggmpg§itign; A plastic monofilament was used as

opposed to a traditional cotton filament to eliminate changes
in filament length associated with changes in the relative
humidity of the environment (Penney et al., 1973) . The
monofilament was tied to an elongating internode using a slip

knot.

126

e' ss: Because of the rather slow rate of
rotation of the shaft, the torque necessary to start rotation
of the shaft was considered as opposed to the torque necessary
to move an already rotating pulley. The minimum torque
necessary to turn the shaft is 5 g—cm. The relationship
between the minimum force necessary to turn a pulley and
pulley diameter is shown in Figure 4. The force which is
employed to turn the pulley is gravity, i.e. a counterweight.
A counterweight which is to light will fail to turn the shaft
and register any stem elongation. If the counterweight
necessary to turn the shaft was so heavy that the elongation
of the plant was affected a count-counter weight can be
attached to the monofilament between the plant and the pulley

to reduce the tension.

W The system was subject to

fluctuation in output voltage with changes in system
temperature. Because of this and unknown factors which may
affect the output of the transducer other than stem
elongation, one transducer per chamber was employed as an
internal standard. The internal standard was composed of a
fixed weight, a monofilament, and a counterweight similar to
the transducers measuring stem elongation. Internal standard
output was subtracted from data collected from transducers
measuring plant stem elongation to account for environmental

effects on transducer output. Care was taken to make sure

127
that the length of the monofilament on the internal standard

was similar to those attached to the experimental plants.

SystgmLngglgtigni_ The system had a resolution to 2 uM per 5

min measurement period. This determination was made by

determining the fluctuation in the readings of all transducers
when they were connected to glass rods and temperatures were
fluctuated between 10 and 30°C. The internal standard was
used to smooth the data.

The pulleys to determine the resolution of the system
were 4.0 i 0.2 cm in diameter. As pulley size increased, the
resolution of the system decreased. Conversely, a smaller

pulley diameter increased the resolution of the system.

Advantages Of This System

The advantages of this system compared to other systems
which have been developed are :

1) ADT apply less pressure to the elongating region of
the meristem, LDT have both thread and core weight. The core
weight is often at least 4 g. ZLDT which employ a spring, also
have the pressure which is exerted by the spring potentially
affecting elongation. In addition, if a spring is employed,
the pressure on the meristem is variable. The basis for this
is based on the equation: F=kx where F=force, k=is a
constant which is a measure of the stiffness of the spring,

and x=the distance between full extension and contraction of

128
the spring (Sears et al., 1982). Since the force applied by
a spring is directly proportional to x, the force which is
placed on the meristem varies.

2) This system employs an internal standard. The
internal standard accounts for all effects in transducer
voltage output which may result from the environment on
electrical and physical components of the system. Such
variations in transducer output were found within this system
and have been found in previously developed systems (Lecharny
et al. , 1985) . No other systems using transducers have
employed an internal standard to minimize such potential
sources of error.

3) The software utilized.by this systemwwas advantageous
in that:

a) Data was filtered to remove extraneous
‘noise'.

b) Data were converted into meaningful units.

c) Data was collected every 3 seconds and is
averaged every 5 minutes. Therefore, a
considerable number of measurements were
taken, thereby, increasing the reliability of
the data.

d) A number of other useful parameters were able

to be saved with the transducer data.

129
e) Data was written to the hard disk in a
fashion which was directly readable by ‘Lotus
1-2-3' for analysis.
f) The software was written in ‘Basic' which
allowed program modification by the researcher.
g) Often data files are so large that they
could not fit on a standard floppy disk. The
software included a program which broke
files into usable sizes for combination after
analysis.

4) The system employed simultaneous measurements on 3
transducers per chamber which were directly comparable to 3
transducers in an adjacent chamber. Therefore, data were
compared across time which was the case with most studies
which utilized transducers. The chambers themselves were
synchronized and were run by internal computers which yielded
precise environmental control.

5) The use of ADT offered a variable useful distance
before the system had to be reset, i.e. the pulley size could
be changed depending on the experiment length and the amount
of elongation which was expected. For instance, etiolated
seedling elongation may be so rapid that LDT systems may have
to be reset more than once a day. LDT often have a maximum
range of 20 mm 1 0.01 mm (Lecharny and Wagner, 1984). ADT

offer more flexibility in this respect.

130

Literature Cited

Addink, C.C.J., and G. Meijer. 1972. Kinetic studies on the
auxin effect and the influence of cyclohexamide and blue
light. In Plant growth substances 1970. Ed. D.J. Carr,

Springer-Verlag, Berlin.

Assaad-Ibrahim, C., C. Lecharny, A. Millet, and B. Millet.

1981. Circadian endogenous growth rhythm in tomato.

Plant physiol., 67 (Suppl.):113

Ball, W.G., and I.J. Dyke. 1954. An endogenous 24 hour

rhythm in the growth rate of the Aygng coleoptile. g;

532: ﬂgt. , 5:421-433.

Ball, W.G., I.J. Dyke, and. M.B. Wilkins. 1957. The
occurrence of endogenous rhythms in the coleoptile in

various cereal genera. QL_EXQL_EQ§L, 8:339-347.

Christ, R.A. 1978. The elongation rate of wheat leaves. II.

Effects of sudden light change on the elongation rate.

l1_E321_BQ£1: 293511-613-

De La Fuente, R.K., and A.C. Leoplold. 1970. Time course of
auxin stimulations of growth. Elant_£ny§lgl&, 46:186-

189.

 

131
Evans, M.L., and P.M. Ray. 1969. Timing of the auxin

response in coleoptiles and its implications regarding

auxin action. J, Gen. Physiol., 53:1-20.
Hsiao, T.C., E. Acevedo, and D.W. Henderson. 1970. Maize
leaf elongation: continuous measurements and close

dependence on plant water status. Science (Wash.) ,

168: 590-591 .

Lecharny, A. , and R. Jaques. 1982. Photoinhibition of
internode elongation rate in light grown Vigna sinensis
L. Control by light quality. Plant Cell 3:121:03. , 5:31-
36.

Lecharny, A., and R. Jaques. 1980. Light inhibition of

internode elongation in green plants. A kinetic study

with Viggg slngnsig L. W, 149:384-388.

Lecharny, A., and E. Wagner. 1984. Stem extension rate in

light-grown plants. Evidence for an endogenous circadian

rhythm in mm. W. 60:437-
443.

Lecharny, A., M. Schwall, and E. Wagner. 1985. Stem
extension rate in light-grown plants. 1 n s' .,

79 : 625-629 .

132
Penny, D., P. Penny, and D.C. Marshall. 1974. High
resolution measurement of plant growth. Ca . o ,

52:959-969.

Sachs, J.V., 1874. Textbook of Botany. (transl. by 8.11.

Vines, 1882). Clarendon Press, Oxford, Eng.

Sears, F.W., M.W. Zemansky, and H.D. Young. 1982. College
Physics. 5th Ed., Addison-Wesley Pub. Co., Reading,

Massachusetts. pp. 109, 183.

Sweeney, B.N. 1969. Rhythmic Phenomena in Plants. Academic

Press, London. pp. 1-59.

Verbelen, J.P., E. Spruit, E. Moerells, and J.A. DeGreef.

1981. Endogenous rhythmicity in etiolated 13mm

seedlings. Biol. Jaarb,, 49:190-199.

133

Figure 1. A schematic representation of the circuit block

diagram of an angular displacement transducer.

134

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135

Figure 2. Schematic diagram of a system developed to
continuously measure plant stem elongation. Only one
transducers is shown, however, a total of 8 transducers
were employed in 2 growth chambers. All transducers were

controlled by a single microcomputer.

136

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TNPUT VOLTAGE “POWER

SOURCE

TRANSDUCER ? OUTPUT VOLTAGE

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PLANT PLANT TEMP
SOIL TEMP
COMPUTER
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137

Figure 3. The output function of an angular displacement

transducer. Note the typical linear range.

138

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139

Figure 4. The effect of increasing pulley diameter on the
usable distance for direct linear measurement and the
minimum mass required to turn the transducer shaft. The
usable distance was calculated by dividing the
circumference of the selected diameter pulley by 6 to
yield the linear 60° distance. The maximum torque
required to start rotation of the shaft is 5 g-cm. If
this is held constant the minimum counterweight mass
could be calculated from the equation: Torque (N-m) *

Moment (m) = Mass (N) (Sears et al., 1982).

140

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141

Section VII

Appendices

142

Appendix A

Temperature Effects

ncata ‘Madisto' Flower Initiation

143

Temperature Effects
MW ‘liadisto' flower Initiation

John Erwin, Royal Heins, Robert Berghage, and Brian Kovanda
Department of Horticulture

Michigan State University

East Lansing, MI 48824 U.S.A.

112511351

W ‘Hadisto' plants were grown under 19 different
day/night temperature (DT/NT) environments ranging from 10°C to 30°C with a 9
,hour photoperiod. Time from initiation of $0 to anthesis varied from 50 days
-in the 20C DT/ 25°C NT environment to 99 days in the 10°C 01’] 15°C NT
environment. Flower initiation did not occur when plants were rown under
the following DT/NT temperature environments, 10°/30°C, 30°/10°C, 25 [25°C, and
30°/30°C. Instead, only phylloclades developed. Plants grown in other
environments had only flowers or both flowers and phylloclades. An optimal
temperature for flower initiation, based on the ratio of flowers to phyllocl ades,
existed at 20°C. Phyllocl ade number increased as DT increased and as DT increased
relative to NT. Phylloclade number was greatest in the 30°C DT/lO’C NT
environment. -

1.4mm

. m r r n Haw. plants are induced to flower by placing plants
under short days (Roberts and Struckmeyer, 1939). Flower initiation is often
incomplete, i.e. both flowers and phylloclades develop.

One environmental factor which influences W flower
initiation is temperature (Ranger and Filhrer, 1981). Roberts and Struckmeyer
(1939) reported that flower initiation was inhibited under short days (SD) when
day and night temperature exceeded 21-24°C, was promoted by SD between 17-18’C,
and occurred under $0 or long days (LD) at 13°C. Ranger and Fuhrer (1981)
reported that the higher the temperature, the shorter the photoperiod necessary
to induce flowering. At 30°C, an 8-9 hour photoperiod was required to induce
flowering. Yonemura (1979) determined the critical photoperiod for flower
induction was 12 hr at 18-20‘0.

Incomplete flower initiation, i.e. simultaneous development of phylloclades
and flowers, is probably due to nonoptiaal photoperiod/temperature conditions
for maximal floral induction. The objective of the research presented in this
paper was to determine the relationship between temperature and the degree of
WI! flower initiation under a 9 hr photoperiod.

Three Wm Haw. ‘Madisto’ plants per 10.2 cm plastic pot
were grown in a glasshouse with a 20° 1 2°C air temperature. Eighty pots were
selected for pl ant uniformity, pl ants were pinched to 3 phyllocl ades (leveled),
and pots were then moved to glasshouses with temperature setpoints of 10, 15,
20, and 25°C. Pl ants were moved among glasshouses at 0800 and 1700 hr each day
to yield a total of 16 day/night (DT/NT) temperature combinations. In addition
to the 16 DT/NT combinations, plants were placed in 10°/10°C, 10°/30°C, 30°/10°c,
and 30°/30°C DT/NT environments. Each temperature treatment had 5 replicates.

Movement of plants required approximately 15 minutes. An opaque curtain
was pulled over the pl ants after they were moved at 1700 hr and was retracted
prior to 0800 hr to provide a 15 hr scotoperiod (9 hr photoperiod) paralleling

144

'the NT treatment. ~

Date of anthesis, flower number, and p lloclade number were collected at
anthesis on each pot. Data were statistica ly analyzed as a 4 x 4 factorial
model with OT and NT as the main factors.

The time from induction (start of $0) to anthesis decreased nonlinearly from

100 to 52 days as the average dail temferature increased from 12°C to 20°C
(figure 1). Increasing ADT above 20 di not hasten floweriﬁng;

F owerinitiation did

not occur when both OT and NT

 

 

  

 

 

 

n
-were warmer than 25°C. These g 110
'results contrast research by 5 ,
Ranger and Fuhrer 1981) 5 100. Y - 5317.57 . .(--3595"') + «.3
which showed that ower o . r‘ - .97
initiation occurred at 30°C v- 90-
with an 8-9 hr photoperiod. g ‘
Poole (1973) also showed that 2 30‘
flowering could occur at g 70: -
temperatures above 23°C. '2 .
Differences between this " 60-
experiment and that of Ranger g .
and Fuhrer (1981) and Poole L: 50* a Treatment Means
(1979) may be due to m 40i — Regression Function
differences in the g; ,2 ' 1'4 1‘3 ' (a ' 2'0 2'2 24

sensitivity of different
cultivars to temperature

Average 00in Temperature (°C)
and/or photoperiod.

 

 

 

Figure 1. The effect of average daily
"19m temperature (NT) temperature on the time from flower

affected the degree of flower induction t0 9311110318 on W
initiation. Day temperature mm ‘mdi‘t°'-

(DT) had no significant
effect on the degree of
flower initiation. The
optimal NT range for flower
initiation, based on the
ratio of flowers to
phyélloclades, was from 15 to
20 (Figure 2). As NT
increased above 20°C or
decreased below 15°C, flower
number decreased and/or
phyl l ocl ade number increased .
These data agree with
research of Yonemura (1979)
who suggested that the . , . ,
optimal temperature for 5 10 15 20 25 30 35
flower initiation was lS-ZO’C . T °C

when plants were grown with ”'9'“ emperoture( )

a 12 hr photoperiod; no
distinction between day and .
night temperature was made. Figure 2. The effect of night temperature on the
Similarly, Ranger and Fuhrer ratio of flowers to flowers plus phylloclades on '
(1981) suggested that the Wm ‘Hadisto'.

Optimal temperature for

 

 

1.0-
0.8d
0.6-

0.4-i

 

 

 

 

FiowerS/(Flowers + Phylloclades)

 

 

 

O

O

145

flower initiation was 153C during the first week then increased to 180C during
the second week of induction.
Total break and phyllocl ade number per pot increased as 0T increased (Tables
1 and 2). For instance, phylloclade number increased from 1.8 to 33.0
phylloclades per pot as DT increased from 10 to 30°C with a 10°C NT. Phyllocl ade
number per pot was also reater when the DT was greater than the NT with DT over
250C. For instance, phy loclade number was lower when plants were grown with a
30°C DT/ 30°C NT environment (19.4 phylloclades per pot) than when pl ants were
grown with a 30°C DT/10°C NT environment (33.0 phyllocl ades per pot). The effect
of’DT on phylloclade number is in agreement.with research by Runger (1979) which
determined that phyllocl ade number increased with temperature up to 30°C.

The authors appreciate the technical assistance of Joy Hind, Hendy Cole.
Mark Smith, and Martin Stockton. Plants were donated by Post Gardens of Battle
Creek, Battle Creek, Michigan.

5.414331111191131
Poole, R.T. 1973. Flowering of Christmas cactus during the summer.
HPLtSslense 8:186.

Roberts, R.H., and 8.E. Struckmeyer. 1939. Further studies of the effects of
temperature and other environmental factors upon photoperiodic responses
of plants. J. Agr, 3:5. 59:699-709.

Ranger, 1!. von. 1979. Vegetative growth of W, and 219.95.45.11:-
ﬁartsohamzmhaﬂ 44(6l:24l-246-

RDnger, 11. von., and H. Fuhrer. 1981. Daylength, temperature, and

flowering reaction of Sunbeam and 219mm. BMW
45(5):209-213.

Yonemura, K. 1979. Studies on the control of flowering in Christmas cactus.
, Aichi, Japan.

146'

Table 1. The effect of d and night temperature on total break
number per pot of Szglgmhgrggna_tnnn§atg cv ‘Hadisto'

 

e I 1"—
Day Temperature" (°C) ' q _'
Night --------------------------------------~: .......
Temperature (°C) 10 15 20 25 ' 30
10 2.4 ’ 11.0 18 6 19.4 33 0
15 6.6 8.8 11 s l3e2 '
20 10.2 11.8 13.4 12.4 -
25 9.8 9.6 10 8 19.6 -
30 4.6 - - - 19.4
Significance

Day Temperature
Linear *** V
_Quadratic n.s.

Night Temperature
Linear n.s.
Quadratic ‘ n.s.

' Numerals represent treatment means.
’ Significant at P . 0.001 (***): not significant (n.s.).

Table 2. The effect of day and night temperature on phylloclade
number per pot of S;h1gmhgrgg:3_lzgnggli cv ‘Nadisto'.

Day Temperature (°C)
Night ...............................................

Temperature (°C) 10 15 20 25 30

Significance
Day Temperature
Linear *** V
Quadratic n.s.

Night Temperature
Linear n.s.
Quadratic n.s

' Numerals represent treatment means.
’ Significant at P - 0.001 (***); not significant (n.s.).

I. "

147

Appendix B

Thermomorphogenesis And Photoperiodic

Responses Of nephrglepi§_gxalt§ta ‘Dallas Jewel'

148

Thermomorphogenic And Photoperiodic Responses
of WW ‘Dallas Jml'

John Erwin, Royal Heins, Robert Berghage, and Brian Kovanda - --
Department of Horticulture

Michigan State University

East Lansing, Ml 48824 U.S.A.

Must

- W ‘Dallas Jewel' plants were grown under 2 photoperiods
for 92 days under 16 different day/night temperature environments with
temperatures ranging from 15 to 30°C. Plant morphology was influenced by both
temperature and photoperiod. Frond length increased from 9.8 to 17.8 cm on
pl aqts grown under short days (SD) and 9.3 to 21.9 cm on plants grown under long
days (L0) as average daily temperature (ADT) increased from 15 to 30°C. Leaflet
number per frond increased from 25 to 37 on plants grown under $0 and 23 to 42
on plants grown under L0 as ADT increased from 15 to 30°C. Stolon number was
greatest on plants grown under SD and was greater when day temperature was less
than the night temperature.

Plant development rate was also influenced by temperature and photoperiod.-
Frond unfolding rate increased from 0.14 to 0.38 fronds per day on plants grown
under 50 and 0.07 to 0.26 fronds per day on plants grown under L0 as ADT
increased from 15 to 30°C.

Therefore, SD grown plants had more fronds which were shorter in length
and had fewer leaflets per frond than LD grown plants. Total leaf area per
plant, calculated from leaflet area, leaflet number per frond, and frond number,
was not significantly different between $0 and LD grown plants.

r u

Plant morphology is influenced by day temperature, night temperature, and/or
the relationship between day and night temperature, i.e. plant growth is
thermomorphogenic (Erwin et. al., 1989). For instance, stem elongation is
primarily dependent on the relationship between the day and night temperature
(Erwin et. al., 1989; Karlsson et. al., 1989). In contrast, leaf area and
shape are typically a function of absolute day and/or night teamerature (Njoka,
1957: Erwin et. al., 1989).

Pl ant development rate is often a function of average daily temperature in
a limited temperature range (Karlsson et. al., 1989; Alm et. al., 1988). The
rate of leaf unfolding typically increases to a maximum rate then decreases as
average daily temperature increases. For instance, poinsettia (Berghage et. al .,
1989) and fuchsia (Erwin et. al ., 1989) leaf unfolding rate increases to a maxima
at an average daily temperature of approximately 25°C, then decreases as
temperature increases above 25°C.

Little is known on the effect of temperature and photoperiod on fern
develOpment. The objective of this research was to determine how temperature
and photoperiod influence 11.211111111111115 morphology and development rate.

112W; ‘Dallas Jewel' plants were planted in 10.2 cm plastic
pots on 8 October, 1988, in a medium consisting of equal parts of sphagnum peat,
perlite, and vermiculite. Plants were growth for 2 weeks in a glasshouse ' '
maintained at a 20°C + 2°C air temperature. Plants were then selected for

O

149

uniformity based on frond number and size and moved to glasshouses with
temperature setpoints of 15, 20, 25, and 30°C. Half of the plants within each
glasshouse, 16 plants, received a long day treatment which consisted of night
interruption lighting from 2200 t3 0200 hr delivered with incandescent lamps at
an. intensity of 2 micromol s' ' m" .

Plants were moved among glasshouses at 0800 and 1700 hr each day to yield
a total of 16 day/night temperature combinations within each photoperiod. Each
treatment had 4 replicates. Movement of pl ants required 15 minutes. An opaque
curtain was pulled over the plants after they were moved at 1700 hr and was
retracted prior to 0800 to provide a 9 hour photoperiod paralleling the day
temperature treatment. Light pollution between long and short days pl ants within
a glasshouse was eliminated by pulling an opaque black curtain between the pl ants
at 1700 and retracting the curtain at 0800 hr.

Frond number, frond length, leaflet number per frond, leaflet length and
width, and stolon number were collected after 92 days on each plant. Frond
length and leaflet number were collected on a fully expanded representative
frond from each plant. Leaflet length and width were collected from a single
leaflet on the representative frond from each plant.

Data were statistically analyzed as a‘4 x 4 x 2 factorial model with day
temperature, night temperature, and photoperiod as main factors. Significance
of environmental parameters was determined using analysis of variance and
multilinear regression analysis.

e n icus n

3,], Morphology;

Frond length and leaflet number per frond were a function of average daily
temperature (ADT) and photoperiod (Table l). Frond length increased as ADT
increased from 15 to 30 C regardless of photoperiod. In addition, frond length
was longer when pl ants were grown under'long days (LD) compared to pl ants grown
under short days (SD). The increase in frond length due to 'L0 may be a response
to light quality or light duration. Further experimentation will address this
question.

Leaflet number per frond increased as ADT increased from 15 to 30°C (Table
1). In addition, leaflet number per frond was greater when plants were grown
under LD than when pl ants were grown under 50.

The minimum recommended night temperature (NT) for growth of MM
is 16°C (Joiner, 1981). One means to evaluate growth of foliage plants is by
comparison of leaf area among pl ants. Research presented in this paper suggested
that the optimal ADT for Wt; ‘Dallas Jewel' leaf area was 25°C
(Table 1). Stolon number was influenced by OT and NT (Table 2). Stolon number
decreased in a curvilinear fashion with significant linear and quadratic terms.
In contrast, stolon number increased as NT increased. Photoperiod had no
significant effect on stolon number.

Frond unfolding rate increased as ADT increased from 15 to 25°C, then
decreased as ADT increased above 25°C (Figure 1). A maximum frond unfolding rate
at 25°C is similar to the response of leaf unfolding rate to temperature observed

in JWWM (Berghage et al, 1989), £93 (Friend et al, 1962), and

 

 

fuchsia mm (Erwin, unpublished data) where leaf unfolding rate increased

to 25 C then decreased as temperature increased above 25°C.
Frond unfolding rate was greater when pl ants were grown under 50 than under

LD at a comon ADT. There was no significant difference between the leaf area .

of LD and SD grown plants (Table 1).

O

O

150

 

 

 

 

 

 

5‘ 0.6
O, a Short Day 0
h -—- SD Regresﬂon Funcﬁon
‘1’ 0'5- o Lon Da
0_ g ys O
0 -- LD Regresﬁon Funcﬁon
.u 0.4-
o
m 4
0‘ 0.3-
.E
32
o -
. E 0.2 -
:3 ‘ I
U 0.1 _ ,' so Rate:(.066579tX)—(.000033-X’)-0.76
/ _
g .31 LD Rate:(.087286tX)—(.OOOO46PX’)-l.ll
L: 0.0 Q I ' l ' T ' I ' l '-T f I ' 1 '
l4 16 18 20 22 24 26 28 30 32
Average Daily Temperature (°C)

 

 

 

Figure 1. The effect of average daily temperature and photoperiod on frond
unfolding rate of ngh;glgpi§_exglt§tg ‘Dallas Jewel’.

The authors appreciate the technical assistance of Joy Mind, Mendy Cole,
Mark Smith, and Martin Stockton. Plants were donated by Green Circle Growers
Inc. of Oberlin, Ohio.

W

Berghage, R.D., R.D. Heins, and J.E. Erwin. 1989. Quantifying leaf unfolding
“03h. poinsettia. 89.11.119.111... in ‘Symposium On Bedding And Pot Plant
Pr uction’.

Elvin, J.E., R..U Heins, and M.G. Karlsson. 1989. Thermomorphogenesis in
LﬂJmJgngjﬂgum Thunb. ‘Nellie Nhite’. M 76(1):47-52.

Friend, O.J.C., V.A. Nelson, and J.E. Fisher. 1962. Leaf growth in marquis
wheat, as regulated by temperature, light intensity, and daylength. Can.
J. Bot. 40:1299-1311.

Karlsson, M.G., R.D. Heins, and J.E. Erwin. 1988. Quantifying temperature
T

controlled leaf unfolding rates in r hunb. ‘Nellie '

White’. ,1. Amer, 59;. um. 5:1. 113(1):70-74.

151

'Karlsson, M.G., R.D. Mains, J.E. Erwin, and R.D. Bergha e. 1989., Development
rate during four stages of chrysanthemum growth as etermined by preceding

and prevai ing temperatures. W31. 114(2):234-240.

Kreebla, T, M. Clay, 0. Crater, and G. Smith. 1975. Growing ferns. University
Of Georgia Extension Bulletin, Bull. "37.

Moe, R., R.D. Heins, and J.E. Erwin. 1989. The response ”W
to day and night temperature, light quality, and growth regulators.
W

‘ NJoka, E. 1957. The effect of mineral nutrition and temperature on leaf
2 _ shape in W. New Phytologist 56:154-171.

Table 1. W13!!! ‘Dallaa Jawal' rm tenth, leaflet radar par
frond and leaf area. naylnth was 9 hall-a. The long day traatmant consisted
of nlﬂnt interruption liditlm fr? 3” to 02” hr delivered with 1mm
leaps at an intensity of 2 mol a m . frond length ard leaflet radar data
were collected on a representative frond on each plant.

 

Average Daily Tamarature (’0)

Frond L-Igth (cl)
Short pm 9.13 ' 11.6 16.
Long Days 9.3 .

Temperature
Linear '“ y
Quadratic n. a .
Photoperiod '"

Leaflet Wider Per Fr“
Short Days
Long Days

0101
‘6‘
3

42

Tmratwa
Linear 9"
Matte n.s.
Photoperiod m

Leaf er- ear rune teal: '
M Om 3,629 4,”! 10,845 12,147
I." Days 1,720 9,121 14,648 _ 13,091

Twaratu'e
linear

‘ Minerals rapraamt treatment means.

V Significance at ”.001 (m), not ainifieant (n.s.)

' Leaf area was calculated by mltiplyiro leaflet area by leaflet
W par frond by frond radar.

 

152

Table 2. The effect of day tqaratu-e, niﬁt tdaratu-a mi
photoperiod an W inallaa Jawal' atelan radar.

m Tumor-m r'ci 7'
"*' 33‘ -- :--- c- -- -- ___:__

 

"denture (.8) 19 an 8 30
15 .
am om ' 0.3 1.0 5.3 n.s
Long Days 0.0 0.5 0.2 0.3
20
Short Days 9.0 7.3 3.0 0.0
Lang Days 3.0 2.0 2.0 1.0
25
Short bays 15.0 14.0 10.3 0.0
Lang Days 4.0 0.0 7.9 1.3
30
Short Days 10.0 10.0 13.0 3.0
Lou Days 9.0 11.0 15.0 9.!
Day Tdaretwe
Linear 9
MI": "
Midst Tqaratura
Linear ”9
Matic .. n.s.
Photoparied n.s.

 

Short days were based on a 9 hour wotoparied. Long days were
delivered as a 9 hour photoperiod plu a 4 hr nidlt interruption.
Y Significant at P-OJSC'): home"); P-0.001(”'): not
significant (n.s.).

153

Appendix C

Temperature Effects Sex

Expression In Qusurbitaceae

154
Table 1. Effect of temperature and light fluctuations on
ggggmi§_§atlya cv Tay-Belle sex expression. Plants were
grown for 60 days. Temperature and/or photoperiod length
was 12 hours. Light intensity was 150 micro males 8'1
m'z. In the ‘constant light-fluctuating temperature'
treatment, temperatures fluctuated between 23 and 17W3.

Temperature was constant 20°C in the ‘constant

temperature-fluctuating light' treatment.

 

Flower Number
Environmental .........................
Treatments Female Male Ratio
Constant Light

Fluctuating Temperature 2.7 i 2.1 5.6 i 2.3 0.48 ‘

Constant Temperature

Fluctuating Light 1.7 i 0.5 1.3 i 0.8 1.31
17°C Day Temperature
23°C Night Temperature 2.0 i 0.7 2.0 i 1.4 1.00
23°C Day Temperature
17°C Night Temperature 0.4 1; 0.5 5.6 i 2.1 0.07

 

‘ Female Flower Number] Male Flower Number

155

Appendix D

Temperature And Photoperiod Effects

On Plant Chlorophyll Content

 

156
Table 1. The effect of daty temperature and night temperature
on chlorophyll a, chlorophyll b and p chlorophyll content
of £39h§1a_x_hybziga cv Dollar Princess grown under a 9

hour photoperiod.

 

Day Temperature (°C)
Night ......................................
Temperature (%3 12 16 20 24

‘chlorophyll a' ‘

12 .073 .065 .078 .076
16 .077 .080 .069 .080
20 .070 .066 .065 .064
24 .060 .055 .067 .064
‘chlorophyll b'
12 .021 .021 .026 .024
16 .023 .023 .021 .025
20 .018 .019 .020 .025
24 .015 .016 .019 .020
‘p chlorophyll‘
12 .008 .007 .009 .005
16 .008 .007 .007 .005
20 .004 .007 .006 .006
24 .005 .007 .006 .007

157

Table 1. - continued

chlorophyll a/b ratio'

12 3.41 3.18 3.04 3.13
16 3.40 3.47 3.29 3.24
20 3.96 3.38 3.22 2.60
24 3.90 3.35 3.57 3.26

 

‘ Chlorophyll content was expressed in ug ch

 

158
Table 2. The effect of daty temperature and night temperature
on chlorophyll a, chlorophyll b and p chlorophyll content
of £u§n§13_x_nybzig§ cv Dollar Princess grown under a 12

hour photoperiod.

 

Day Temperature (°C)
Night ......................................

Temperature ( °C) 12 16 2 O 24

‘chlorophyll a' z

12 .075 .067 .069 .071
16 .066 .058 .069 .060
20 .060 .059 .064 .055
24 .045 .046 .056 .054
‘chlorophyll b'
12 .024 .021 .023 .024
16 .019 .019 .020 .020
20 .016 .018 .022 .019
24 .012 .013 .017 .017
‘p chlorophyll'
12 .010 .007 .009 .007
16 .006 .006 .004 .006
20 .005 .006 .007 .006
24 .006 .004 .006 .005

159

Table 2. - continued

chlorophyll a/b ratio'

12 3.14 3.22 2.95 2.94
16 3.52 3.09 3.37 3.04
20 3.71 3.20 2.99 2.96
24 3.59 3.61 3.25 3.15

 

‘ Chlorophyll content was expressed in ug cm'2

160
Table 3. The effect of daty temperature and night temperature
on chlorophyll a, chlorophyll b and p chlorophyll content
of Qendranthema grandiflgrg cv Bright Golden Anne grown

under a 9 hour photoperiod.

 

Day Temperature ( °C)
Night --------------------------------------
Temperature (%3 12 16 20 24

‘chlorophyll a' z

12 .081 .084 .082 .073
16 .071 .089 .088 .074
20 .057 .064 .064 .097
24 .086 .081 .079 .074
‘chlorophyll b'
12 .026 .028 .025 .018
16 .021 .026 .024 .024
20 .013 .017 .017 .025
24 .027 .023 .024 .022
‘p chlorophyll'
12 .003 .005 .002 .002
16 .002 .003 .002 .002
20 .001 .002 .002 .002
24 .002 .002 .002 .002

161

Table 3. - continued

chlorophyll a/b ratio'

12 3.13 3.04 3.23 4.05
16 3.45 3.42 3.67 3.11
20 4.39 3.74 3.75 3.83
24 3.24 3.56 3.31 3.27

 

l

Chlorophyll content was expressed in ug cm'

162
Table 4. The effect of daty temperature and night temperature

on chlorophyll a, chlorophyll b and p chlorophyll content

of Eelargonlm hortorm cv Red Elite grown under a 9 hour

 

photoperiod.
Day Temperature (°C)
Night --------------------------------------
Temperature (°C) 12 16 2 O 24

‘chlorophyll a' ‘

 

12 .047 .052 .043 .045
16 .045 .047 .047 .046
20 .050 .042 .049 .045
24 .038 .027 .036 .036
‘chlorophyll b'
12 .014 .017 .013 .015
16 .013 .014 .015 .015
20 .014 .013 .017 .014
24 .009 .009 .012 .012
‘p chlorophyll'
12 .003 .003 .002 .003
16 .003 .003 .002 .003
20 .002 .003 .003 .002
24 .002 .003 .002 .003

Table 4.

12

16

20

24

163

- continued
chlorophyll a/b ratio'
3.42 3.14 3.21 3.12
3.41 3.22 3.04 3.05
3.62 3.25 2.95 3.22
4.13 2.91 3.04 2.86

 

Chlorophyll content was expressed in ug cm‘

2

164

Appendix E

The Effect Of Day And Night Temperature

On Stem Elongation Of Micellaneous Species

165

Table 1. The effect of day temperature, night temperature,

and photoperiod on Xantnigm_§tzgmgzigm internode length

(cm). Photoperiod was 9 hours long (short day) or 9
hours plus a 4 hour night interruption with incandescent

lamps (long day).

 

Day Temperature ( °C)

Night """""""""""""""""""""""""

Temperature (°C) 1 6 2 0 2 4

16

20

24

16

20

24

‘Short Day'
0.9 i 0.1 1.4 i 0.2 1.4 i 0.1
0.6 3; 0.1 0.9 1 0.1 1.0 i 0.2
0.5 i 0.1 0.7 i 0.1 0.9 i 0.1
‘Long Day'
1.3 i 0.2 1.9 i 0.1 2.2 i 0.1
1.2 i 0.1 1.8 i 0.2 1.9 1 0.1
0.9 i 0.1 1.6 i 0.1 1.7 i 0.2

 

166
Table 2. The effect of day temperature, night temperature,
and photoperiod on Qucumls satim internode length (cm) .
Photoperiod was 9 hours long (short day) or 9 hours plus

a 4 hour night interruption with incandescent lamps (long

 

day).
Day Temperature (°C)
Night ------------------+ -------------------
Temperature (°C) 16 2 0 2 4
‘Short Day'
16 0.8 i 0.2 4.1 + 0.6 6.8 i 1.3
20 1.6 i 0.5 3.6 i 0.6 5.0 i 0.9
24 1.1 i 0.1 2.0 i 1.2 3.8 i 0.2
‘Long Day'
16 1.4 i 0.4 4.4 i 1.0 9.3 i 1.4
20 2.2 i 0.5 5.0 i 0.8 5.8 i 1.0

24 1.5 i 0.1 2.8 i 0.1 5.2 i 0.6

 

167
Table 3. The effect of day temperature, night temperature,
and photoperiod on W internode length
(cm). Photoperiod was 9 hours long (short day) or 9 hours
plus a 4 hour night interruption with incandescent lamps

(long day).

 

Day Temperature ( °C)

Night --------------------------------------
Temperature (°C) 16 20 24
‘Short Day'
16 3.1 2“. 0.4 5.7 i 0.8 7.1 i 0.6
20 3.4 i 0.4 5.9 i 0.1 7.0 i 0.7
24 3.1 i 0.3 4.6 i 0.4 6.4 i 0.5
‘Long Day‘
16 3.3 i 0.6 4.5 i 0.4 5.1 i 0.7
20 3.6 i 0.2 5.7 i 0.4 5.6 i 0.8
24 3.0 i 0.2 4.0 i 0.2 5.5 i 0.3

 

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