CONTRIBUTIONS OP SUNLIGHT TO GREENHOUSE ROSES

by

Edward L. Chandler

A THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

DOCTOR OP PHILOSOPHY

Department of Horticulture
Year

1953

ProQuest Number: 10008277

All rights reserved
INFORMATION TO ALL USERS
The quality of this reproduction is dependent upon the quality of the copy submitted.
In the unlikely event that the author did not send a complete manuscript
and there are missing pages, these will be noted. Also, if material had to be removed,
a note will indicate the deletion.

uest,
ProQuest 10008277
Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author.
All rights reserved.
This work is protected against unauthorized copying under Title 17, United States Code
Microform Edition © ProQuest LLC.
ProQuest LLC.
789 East Eisenhower Parkway
P.O. Box 1346
Ann Arbor, Ml 48106- 1346

ACKNOWLEDGEMENTS
The author expresses his appreciation for help and
encouragement he has received from Dr. H. B. Tukey, Paul
R. Krone, Dr. Erwin J. Benne, Martha Gruber Davidson, and
Elizabeth Clum.
Financial assistance from Roses Incorporated and the
American Society of Florists made possible the development
and completion of this project.

Ferro Enamel Company and

Jackson and Perkins Company liberally donated materials#
A great amount of sincere advisement and encourage­
ment has come from Dr. Donald p. Watson#

CONTRIBUTIONS OF SUNLIGHT TO GREENHOUSE ROSES

By-

Edward L. Chandler

AN ABSTRACT
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Horticulture
Year

Q
Approved

^p
d \

1953

,:- ~ .

^

^

______

Edward L. Chandler

Three plantings of roses were made to study quantitative
and qualitative effects of light intensity on the growth of
Better Times roses.

Growth measured by elongation and

fresh weights of all plant material produced was correlated
to light intensity by means of recording light intensity
over plants growing in shade houses constructed of cloth
and designed to allow 20, 35, and 58 percent incident
radiation to be available.

Total radiation as well as the

reduced radiations was measured by means of a Speedomax
recorder.

Soil surface was covered with a highly reflective

’’frit”, with a less reflective nfritn, and with soil.
Carbohydrate analyses were made of tissue subjected to
three levels of radiation.

Sections of leaves were collected

for an anatomical study of rose leaf development resulting
from various quantities of light.
Total growth of the rose plants was reduced by decreases
in light intensity.

Reduction to 20 percent total solar

radiation reduced growth to an extreme degree, and appeared
to be near the minimum light intensity for growth.

Light

of the magnitude of 58 percent of full radiation allowed
growth to be only slightly reduced.

Judging from growth

produced it appeared as if plants growing in 58 percent
radiation had been supplied with almost as much light as
was ideal for maximum growth.

Any reduction of light below

58 percent of the total radiation resulted in rather sharp
decrease in total growth.

Edward L, Chandler

Surface covers which increase the amount of reflected
light seldom increased plant growth.

Plant growth response

from such indirect light was noted when radiation was
extremely high and then only if plants were very small.
This finding was thought to be related directly to the
amount of shading of surfaces by plant foliage.
Carbohydrate analysis revealed a great increase in
total sugars in leaf and stem tissue during periods of
intense heat and extremely high radiation.

Translocation,

respiration or utilization of carbohydrates were found to
occur in great quantities after periods of dark or cloudy
weather.
Leaf structure was greatly modified by the intensity
of light available to various plants.

Heavy shading

resulted in the development of very thin leaves with
palisade cells of much less depth than those of leaves
subjected to high radiation; total chlorophyll content
appeared to be much greater in leaves obtained from these
plants#
This paper is supplemented by eleven tables and nine
figures#

TABLE OP CONTENTS
Page
INTRODUCTION .........................................

1

LITERATURE REVIEW. .

3

...............................

Light Recording. • • • • * . . • • . • • • • • • • •

3

photoperiod and Quality of L i g h t ..........• • • • •

i|-

Photo synthetic Efficiency. • • • • ..........• • • •

6

Modification of Leaf Structure • • . • • • • • • • •

9

EXPERIMENTAL PROCEDURE ..............................

11

First Experiment

..........

• • • • »

11

Experimental Design ........ . . . . . . . . . .
Collection of Data. • • .......... • • • • • • •

11
13

Second Experiment.

• • • • • • • •

16

Experimental Design • • • • • • • • • • • • • « •
Collection of Data. . • • • • • • • • • • • • • •

16
16

Third Experiment • • • • ............ . . • • • • • •

13

Experimental Design ............................
Collection of Data.
••••

18
18

EXPERIMENTAL R E S U L T S ................

.

20

Experiment One • • • • • • « • • • • • • • . • • • •

20

Experiment Two

22

Experiment Three • • • • • • •

............

....

25

DISCUSSION . . . . . . . . . . . . . . . . . . . . . .

Lj.0

S U M M A R Y . .............................................

i*-6

REFERENCES C I T E D .....................................

l\B

LIST OF TABLES
Table

Page

1

Number of flowers per treatment...............

21

2

Final weight of plants. • • • • • • • • • • • •

23

3

Total weight of plant material, . . • • • • • •

2ij.

ij.

Linear growth as influenced by light
intensity and surface cover . . . • • • • . •

26

5

Quantity and quality of flowers • • • • • • • •

27

6

Growth as influenced by light intensity
and surface cover

30

7

Weight of plant material produced • • • • • • •

31

8

Yield of flowers as influenced by light
intensity and surface cover . • • • • • • • •

32

Light records in foot-candle hours • • • • . .

3k-

10

Measurements of leaf sections • • • • • • . • •

35

11

percentage total sugars and ash in
relation to light intensity o . . . . . . . «

38

9

LIST OP FIGURES
Figure
I

Page
Greenhouse bench with surface covers • • • • •

12

II

Rose plants and soil insulation. • • • • • . .

II4.

Ill

Newly planted rose plants. . • • • • • . . . »

11+

Equipment for weighing and measuring plants. •

lj?

Experimental design. • • • • • • • • • • • • •

17

IV
V
VI
VII

Increment of linear plant g r o w t h ..............
Light intensity graph. • • • • • • • • »

28

...

33

VIII

Cross-sections of rose leaves. . . • • • • o .

37

IX

Variation in total sugars. » • • • • • « • • •

39

INTRODUCTION
Severe reduction in growth of greenhouse roses during
periods of low SDlar radiation has been a perennial problem
in the state of Michigan.

Growers greatly concerned about

this problem have given little thought to light needs in
summer.

The effects on the growth of greenhouse roses from

radiation during the summer, especially during periods of
high temperature, has not been investigated, but during
periods of extremely high radiation it has been the commercial
practice to apply external shade to glass in the greenhouse.
This shading has reduced the impinging light and the
temperatures within the greenhouse.

The quantitative effect

of this reduction of light on the total growth of roses has
not been thoroughly studied.

Data involving only number of

flowers or shoots, as well as records of sunlight hours,
are of limited value.

Quantitative measurements of the

solar radiation have rarely been accompanied by suitable
quantitative growth measurements.
Modification of rose leaves and their carbohydrate
status as a result of varying light intensities have not
been thoroughly investigated and especially is this true
for the high temperature period during the summer months.
The effects of leaf shading and of diffused light on the
growth of rose plants have received little study.

2

This investigation, therefore, was designed to permit:
(1 ) the quantitative correlation of light intensity and
growth, (2 ) the evaluation of varying amounts of diffused
light on the growth of young and old rose plants, (3 ) the
determination of thickness of leaves produced under various
quantities of light, and (I4.) the analyses of the carbohy­
drate status of tissue from rose plants subjected to various
quantities of solar radiation*

LITERATURE REVIEW
Investigations involving plant growth and light have
been directed toward: light quality (Went, 19l|3.)> light
intensity (Davis and Hoagland, 1928), and light duration
(Hamner and Bonner, 1939)»

Many studies have been made on

the effects of light on specific physiological processes*
Some of the more significant results have been published
by Blackmann and Matthaei, 190^5 Sayre, 1928; Shull, 1936;
and Emerson and Lewis, 1939*

Much research has demonstrated

the effect of light on plant growth (Shirley, 1929; Porter,
1936; Went, 1914.1 ).

^

Light Recording
Continuous attempts have been made to increase the
accuracy of light recordings.

Gourley and Nightingale (1921)

employed photographic paper to indicate radiation values.
Using a Macheth Illuminometer, Steinbauer in 1932 period­
ically adjusted intensities of artificial light.

Attempts

have been made to obtain a daily radiation value from a
limited number of periodic readings (Muncie, 1917; Heinicke
and Hoffman, 1933; Christopher, 1931}-; Gray, 193I4.),

The

necessity of having more accurate light readings has
stimulated the development of various types of solar radi­
ation recorders (Post and Nixon, 1939; Crabb, 1950; Hemphill
and Murneek, 1950).

k

Complete works dealing with light measurement are
available in English (Duggar, 1936; DeVore, 1938)*

Radiant

energy nomenclature had been considerably standard!zed by
Withrow (19i|-3) and in 19^0 a thorough compilation of the
literature dealing with recording of solar radiation was
made by Crabb*
The problems produced by the continuous variation of
intensity and quality of solar radiation were recognized
by Shirley in 1931•
Photoperiod and Quality of Lipjit
Light quality ]gas received much attention in recent
years (Popp, 1926a; Emerson and Lewis, 1939; Went, 19^1)*
Ultra-violet light has been found to have little effect on
plant growth in general (Popp, 1926a; Pfeiffer, 1928;
Funke, 1931; Laurens, 1933; Johnston, 1938).

The visible

spectrum was found to be necessary for normal growth, and
the absence of light below j?29 millimicrons reduced the
growth of many species of plants (Popp, 1926a).

Emerson

and Lewis (1939) studied quantum efficiency of photosynthesis
with segregated wave lengths of the visible spectrum.

The

quantity of chlorophyll developed in seedlings has been
shown to vary in plants grown under light of various wave
lengths (Sayre, 1928).
Information contributing to the effect of photoperiod
is voluminous (Garner and Allard, 1920; Deats, 1929; Poesch,
1931; Hamner and Bonner, 1939)*

In 1927 a classical paper

5

by Scarth demonstrated the influence of light on the opening
and closing of stomata in various plants*
Leaf temperature as influenced by light intensity has
received considerable attention.

Shull (1936) has made

measurements of the speed of thermal adjustment in direct
and diffused light.

Wallace and Clum (1938) found the

maximum heating above air temperature to be four, and the
maximum cooling below air temperature to be seven degrees
Centrigrade*
The relationship between light intensity and the
potential for nutrient absorptions was investigated by
Davis and Hoagland (1928).

Alteration of chemical compo­

sition of plants by light intensity has been studied by
Blackman and Matthaei (1905a), Kraybill (1923), Nightingale
(1933) t Street (193l^)» McCool (1935), Mitchell (1936),
and Porter (1936).
The growth response of plants to varying nutrient
levels in relation to different quantities of light has
been reported by Gast (1937) who used conifer seedlings
and found a direct correlation of growth response with
increasing nitrogen when light intensity also increased.
White (1905) using Lemna, found nitrate concentrations for
optimum growth needed to be increased with increasing light
intensity.

This finding has been substantiated by Stein-

bauer (1932), and Post and Howland (19lj.6),

6

Photosynthetic Efficiency
By measuring the increase in dry weight, the photo­
synthetic efficiency of Rosa sp. (Laurie and Witt, 19ip-)»
Lycopersicum esoulentum (porter, 1936), and Pianthus caryophyllus (Holley, 1914-2) has been correlated with various
light intensities.

Black and Matthaei (1905) have shown

that with low light intensity the rate of photosynthesis
is almost directly proportional to the light intensity.
Many workers have reported that increased light intensities
served to increase growth of higher plants (Rose, 1913;
Shantz, 1913; P°PP> 1926a; G a m e r and Allard, 1920),
Shirley (1929) divided a large number of species into ”shade”
and "sun” plants.

He found that at low light intensities

the dry weight was almost proportional to the light intensity
up to 20 percent of full summer radiation.

At higher light

intensities this correlation did not persist,

’’Shade”

plants showed more rapid decrease in growth than ”sun”
plants as a result of their less efficient use of light at
lower light intensities,

Lubimenko (1908), Harder (1921),

and Boysen-Jensen (1929) were in agreement with these results,
Lubimenko, however, found the dry weight of Helianthus sp *
to increase directly with the increase in light intensity
up to full sunlight.
Combes (1910) found the optimum light intensity for the
production of dry matter in plants to increase with increasing
age of the plant.

It is interesting to note that Heinicke

7

and Hoffman (1933) stressed the shading effect of leaves
with increasing age of plants.

The importance of diffused

light as related to shaded leaves was observed by Gray (1934)*
Fifty foot-candles of continuous light were found to
be minimum for growth of Fraxlnus p enn sylvan!ca (Steinbauer,
1932).

Shirley (1929) considered forty foot-candles of

light as the minimum for existence with all species involved
except Helianthus.

Fragaria was found to produce flowers at

500 foot-candles of light but required 1500 foot-candles to
produce fruit (Hedricks and Harvey, 1923)*
Many observations have been recorded involving light
intensities under varying conditions.

Christopher (1934)

used an Illuminometer to take periodic readings of light
striking leaves in various locations on trees.

No leaf on

the north side of the tree was reported to receive over
four percent of the total light of the day.

Readings

recorded during the summer months have been found to exceed
10,000 foot-candles (Boysen-Jensen, 1929)*

Light was

suggested as a factor influencing the number of new lateral
shoots produced by rose plants in varying locations in the
greenhouse (Fischer and Kofranek, 1949).

Light intensity

controlled by position in the greenhouse bench was found to
influence the yield and quality of roses (Rosa sp.) and
Dianthus caryophyllus (Weinard and Decker, 1930).

In a

forest of deciduous trees light readings as low as 0.16
percent of total radiation have been recorded by Salisbury
(1918).

8

Artificial reduction of light has been employed by many
workers in an attempt to measure growth response of plants
to varying light intensities (Shantz, 1913; Kraybill, 1923;
Shirley, 1929; Clements and Long, 1934; G,1*a7> 1934; Mitchell,
1936).
Maximum growth of many species was obtained with 35
and 58 percent transmission of light during June and July,
but during August and September maximum growth was obtained
with full radiation (Arthur and Stewart, 1931)*

Shading of

plants was reported to have no effect on the number of non­
flowering shoots produced by rose plants (Kamp, 1948)*
Hubbell (193^4-) found a decrease in both flowering and non­
flowering shoot production of the rose with decreases in
illumination.

Lower flower production was obtained by

shading Dahlia pinnata but no significant difference was
obtained with shading of Callistephus (Batson, 1933).
Analysis of tissue collected from plants grown under
different light intensities has been made for various con­
stituents.

Carbohydrate, nitrogen, and base element relation­

ships of Pisum grown under various light exposures has been
reported by Street (1934)*

Deats (1925) analyzed Capsicum

frutescens and Solanum esculentum for starch content after
different quantities of light had been supplied to the plants.
Total nitrogen, sucrose, starch and dry matter were deter­
mined for peach and apple trees which had been shaded with
cheesecloth (Kraybill, 1923).

Total sugars were found to

9

decrease in rose tissue when shading was applied (Kamp, 1948) •
The effect of light intensity on quality of growth of
stems and leaves of various plants is of interest*

Deats

(1925) found the height and diameter of the stems of Lycopersicum esoulentum and Capsicum frutescens plants to be
directly proportional to the quantity of light*

Shirley

(1929) working with numerous species of plants correlated
type of growth habit with quantities of light available*
Fresh weight of tomato tissue has been shown to have a
direct correlation with light intensity (Porter, 1938)*
Gray (193U-) related fruit set of sour cherry to light
intensity.

Maximum flowering and fruit set was found to be

considerably delayed by reduced light*

Many species failed

to set fruit with 8 percent total radiation (Shirley, 1929)*
The number of roses produced were in direct relation to the
number of sunlight hours (Muncie, 1917)*
Modification of Leaf Structure
Variations in leaf structure caused by varying environ­
mental factors have been reported by Clements (1904), Hanson
(1917)» Penfound (1932) and Pickett (19i+2)*
Early work by Hanson (1917) showed difference in leaf
structure of Acer and Q.uercus caused by different light
intensities*

Structural modifications throughout the plant

in contrasting light intensities was observed by Penfound
(1932)*

Pickett (1934) concluded that several factors enter

10

into and govern the rate of photosynthesis in green leaves
and that probably one of them is the area of the surfaces
of the exposed cell walls bordering the intercellular spaces#
In 1938» Pickett published results of experiments designed
to determine the amount of chlorophyll in Wealthy and York
Imperial varieties of apples as well as the influence of
the chlorophyll content and the extent of intercellular
space on the amount of photosynthetic activity#

Pickett

and Kenworthy (1939) found that the depth of palisade
mesophyll maintained a definite relationship to the ratio
of the external and internal exposed cell surfaces*

EXPERIMENTAL PROCEDURE
First Experiment
Experimental Design
On May 5, 19^0, four hundred "own-rooted" rose plants
of the variety Better Times were planted in ground benches
in the plant science greenhouse at Michigan State College*
A six-inch depth of Brookston sandy loam, relatively low
in organic matter, was placed in the bench and to this soil
was added one-quarter well-rotted manure and four pounds
of superphosphate.
replicated twice.

Nine plots of 21+ plants per plot were
Most buds had begun to expand on the

plants since they had been cut back.

Bouyoucos plaster

blocks to be used as a guide for moisture content were
placed in each plot.
Three types of surface cover were provided: inert
white "Agricultural Frit""* which in bright sunlight re­
flected approximately 1100 foot-candles of light eight
inches above its surface; black "Agricultural Frit" which
reflected approximately 300 foot-candles; and a thin layer
of Brookston sandy loam which reflected approximately 200
foot-candles of light (Figure I).

A two-inch layer of

glass wool was placed beneath each surface cover to minimize
^Agricultural Frit is the trade name of a fused silica
product manufactured by the Ferro Enamel Company, Cleveland
Ohio.
9

13
©

-P

§
iH
Q*
m
©

03

O
U
bO

C
•H

JB
03
<Ih
13 O
C
3 u
o ©
?■» !>
bO O
33 O

U
O©
<P| o

erf

a «h

•H ?H
.

2

.C l 03

o

Pi erf
©
rQ &
-P

-p
•H
Ih
«h

© *H

s

0 H

©
-p
•rl
£

© £

1 O
©

©

In
C>
H
©

U

•H
ft

03

,

—.
erf

•P
•H
Ih
<iH

x

H
•H
O
©

o
erf
H
,Q

-Q

O

13

soil temperature variations (Figure II)*
A shrimp netting and a camouflage netting were placed
upon light wooden frames to form shade houses for reducing
the amount of direct radiation.

Light was reduced approxi­

mately 75 percent by the camouflage netting and approxi­
mately 55 percent by the shrimp netting*
The plants were grown in the usual commercial green­
house manner (Figure III)*

Periodic applications of ferti­

lizers were made to adjust the nitrate level of the soil
to approximately 25 ppm, phosphate 5 ppm, and potassium
30 ppm, as measured by the Spurway method.

Water was

supplied by sub-irrigation when the level was found to'
be below £0 percent available moisture,
was maintained at 68° F*

Night temperature

Roses were cut at the commercially

recommended cutting stage (petals beginning to unfold),
weighed and measured immediately (Figure IV),
Collection of Data
Flowers and attached stems were cut to the length
required to leave two five-leaflet leaves on the branch*.
Length and weight of stems were recorded immediately after
cutting*

A measurement was made to total monthly increment

of growth by each plant.

After three and one-half months

of growth, existing weights and lengths of the plants were
obtained.
separately.

Roots were washed free of soil and weighed
Light Intensities, obtained by means of a

Figure III.

Figure II.

Rose plants recently planted in
ground bench with surface cover
of soil.

Rose plants recently planted in
soil in ground bench showing
a) planting soil
b) layer of glass wool
c) white "frit” cover

Ill-

i>
H
®

W

•H

3B

1$

16

Weston light meter, were variable and supplied only relative
values of direct and reflected light.

Consequently, they

were used merely as a guide for selecting suitable fabrics
for shading the plants in the second experiment*
Second Experiment
Experimental Design
On September 16, 1950, four hundred dormant roses,
which had been propagated by budding, were planted as In
the previous experiment except that the soil cover of black
frit was omitted.

Six plots of 2lj. plants per plot were

replicated twice with two rows of border plants between
each plot.

The plot arrangement was made as shown in the

experimental design (Figure V),
Cheesecloth replaced camouflage netting used in the
previous experiment to allow more light to reach the plants*
Growth and production records were made for all treatments
as before.
Collection of Data
In order to obtain growth measurements from older
plants, this experiment was continued for two years.

The

plants were pruned severely in May, 195lj and all flower
buds removed until September 1, 1951*

Five and one-half

months later all plants were removed for a comparison of
weight produced over a period of 17 months.

17

EXPERIMENTAL

DESIGN

SOIL

7/HITE FRIT

7

1

w
CO

SOIL

WHITE FRII

8

2

7/HITE FRIT

SOIL

9

3

SOIL

WHITE FRI

4

10

S3
O
M
H
<a!
M
P?
►5
h5

SOIL

WHITE FRIT

11

5
g

SOIL

WHITE FRIT

6

12
Figure V

CO

H
C5

18

Third Experiment
Experimental Design
On March 15, 1952, two hundred roses of the variety
Better Times, propagated by budding, were planted as before*
This provided six plots with 32 plants per plot*

A pre­

viously calibrated and tested Speedomax recorder was
installed using photovoltiac cells as receiving bodies for
the solar radiation.

In addition precision drop coils were

used to allow calibration of the recorder*

One cell was

mounted in a horizontal upright position to measure the
intensity of visible Incident radiation in each of the three
light intensities*

Two additional cells were mounted in

an inverted horizontal position to measure reflected light
in full sunlight 12 inches above the soil covers*
Collection of Data
Leaf and stem tissues were collected before sunrise
and after sunset on June 13, 1
of total sugars*

and 15, 1952, for analyses

All tissue was removed from flowering

branches in the same stage of development.

After having

been dried in an oven at 100° F for three days the material
was ground in a Wiley mill and stored in a desiccator*
After re-drying the tissue, analyses were made by a modified
Munson-Walker gravimetric method.

The remaining tissue

from the samples was dried and ashed by heating at 550° C
for 12 hours*

19

During November one huncred mature five-leaflet leaves
were collected from the top, middle, and base of plants in
each of the six treatments*

Tissues thus obtained were

killed with P.A.A* (5 cc formalin, 5 cc acetic acid, 90 cc
95$ alcohol) and embedded in paraffin.

Cross-sections,

10 micro in thickness, were stained with Conant'3 quadruple
stain.

Leaf thickness and palisade depth of one hundred

leaves collected from each treatment were measured by means
of an ocular micrometer.
The terminal leaflets from mature leaves in the upper
regions of the plant were found to be representative of
the leaflets on the plants in a given treatment.
Fifty free-hand transverse sections were made from
leaves collected during the month of May, 1952, from four
treatments: full sun and heavy shade with frit and soil
covers on each.

Measurements were obtained as before.

On October l5> 1952, all plants were removed and final
weight and elongation records were obtained as in the pre­
vious experiments.

EXPERIMENTAL RESULTS
Experiment One
Greenhouse temperatures higher than 100° F were recorded
often during the summer months when light intensities
within the unshaded greenhouse exceeded 10,000 foot-candles,
the limits of a Weston light meter.

All of the rose plants

continued to grow and produce flowers in spite of these
extreme conditions.

Leaves of plants in 20 percent solar

radiation were extremely thin and pale green.

Many of

the branches were weak and not held erect; flowers were
small and pale in color.

In comparison, plants which were

grown in the 70 percent solar radiation were of better
quality than those grown in the 20 percent, but not as good
as those grown in the full radiation.

Substantially more

flowers were produced on plants growing in full radiation
than on plants subjected to reduced light.

No obvious

differences were found between number of flowers produced
on plants in the 20 percent and the 70 percent radiation
(Table 1)»
Surface cover appeared to have little influence on
flower production in either of the reduced solar radiation
treatments (Table 1),

The number of flowers produced by

young plants under full radiation was greater when the soil
was covered by white "frit” .

No other apparent trends were

21

TABLE 1
NUMBER OP PLOVERS PER TREATMENT
(J4.8 Better Times rose plants grown 10£ days)
Treatment

percent radiation
100
70

20

Soil cover

20£

126

123

Black "Frit" cover

203

125

lilt

White "Frit" cover

290

130

112

22

established in relation to types of soil cover as an
influence on plant weight*
Combined weight of flowers cut, final root weight,
and final top weight (Table 2) substantiate observations
of flower quality and total number of flowers produced*
All weights were much higher for plants grown in full
rather than in 20 percent solar radiation*

No obvious

differences in weight were attributed to the type of soil
cover except a substantial increase in flower weight from
plants grown in full radiation with a surface cover of
white "frit"*
Experiment Two
The plants of this experiment were removed from the
beds for final weights and measurements on April l5, 1952,
17 months after planting*

Weight of plants indicated a

direct relationship to intensity of light*

This was

consistent for root weight, wood removed in cut back, top
weight, flower weight, and consequently, total plant
material produced (Table 3)*
The influence of direct solar radiation was much more
pronounced than that of reflected light*

Reductions in

weight of roots, flowers, and top were greater as a result
of reduced radiation than as a result of type of surface
cover where reflected light was altered*

Those increases

in weight brought about by reflected light were greater in
the full radiation plots than in the shaded plots (Table 3),

23

p

d
©
S
p
ctf
©
d

a
-p
o
E-t

O

IS
OJ
00

P

O
o

ft
Eh

vO

05

CM
co
O'

C\1
o
co
S-

-d CM
if t
-d -

-d o ft
cq
_=f

CO
1ft
vO
CM

o
CM
O'
CM

OJ
rH
rOJ

CO
1ft
vO
ft

o

CM

-d-

eft
rH
O'
OJ

-d■
OrH
OJ

1ft O' CO
0- vO O
Oft -d- vO
i
—i H
rH

vO
1ft

O'

vO

H

o

eft

_d-

O'
OJ

H
CT1
If

1ft vO
f t ' co
CM CO

P
ft
d

ft

tsO
OJ

cm

O'
o
m

CO
O'
1ft
rH

P

d
©

ft

o

01

CM

PINAL

WEIGHT

OP

PLANTS

-P

ft
ft
©

M
0
d

01
©
e

d
©
g
£

EH

d
©
p
p

©
m

3d
o

ft

©
d

&0

d
©

t>
o
o
©
o
cj
rJ
3
m

P

P

ft

ft

d
ft

d

X

©
P

o

£*

ctf

ft

rH

XJ

CQ

rH
*H
O
CO

m

o

rH

XI

PQ

P

XI
bO

©
P

p
xi

bO

•H

d

o

ft

cj

P

tJ

ft

d

oj

■H

cii

tA
a

©

P

cj

d

ft

d
ft

ft

ft

d
o

P

0)

XJ
d

VI.
O
CM

H

ft
O

m

2k

CM
•
rH
GO
■Pf

©
O g
aj s
rD 3
©
-P
H H
O *H

OJ
UN
-p O'
3 rH
O

i—»i

rO
•
cO
cO
CO

1A
o
1A
O
cO

•LA

-d r

CO
•
O'
pdCO

U\
«
O'
XA

vO
•
GO
lA

SO
o
OJ
1A

*
sO
P±

O'
*
OJ
Pi-

O
•
1A
CO

O'
O
•
XA
O'

co
•
O'
O'

o

CO
cO
«
vO

i—1
CO
•
OJ
VO

C'o
«
1A
vO

O'
O'
•
r—
p±

O' ~do- *
O' GO
CO vO

CO
•
00
to

I"
•
OJ
vO

CO
•

O'
•

P
0
o
«

c—
•
rH
O'

Cl

O' Pd•- •

d
p

o

GO
OJ

o

1A
OJ

u

H
K
w
EH

<A
W
t-q
9
E
h

s
s
aPH
o
Eh

S
0
»

Eh
O
Eh

tJ
yj
»H
Fh
©
P,

dd
-p
H
M
o
S
i
oH
cd
Fh
©
>

Fh
©
S
O i—1
H 1A
lit 0s
rH

1A
•
C—
vO

rH

rH

3-

cO

O'
•■ •
0- 1A
tr\ 1A

co

J"
*
rH
XA

O'
*
OJ
H

p±

•
O
rH

O
rH
•■ •
co pdo GO
rH

P
•H
Fh

rH
•H
O
E/3

P
•rH
Fh

rH

•
CM
■LA

p

o

+3
cj
3
rH

O
Eh

P.
U
©
Pj

TO
s
2
u
o

--

3 i—!

CO

-P

rH
•H
O
W

rH

rH

H

Fh

©
i>
O
o
©

o

Oj
<PI
Fh
3

iH
Fh
Ph

TO

-P
©

g
-P
aS
©
u

EH

sd
o
•H
-P
oj

•H
TJ
aJ
Fh
rH
rH
3
£

©
'd
aJ

jd
©

©
d

ccj
dd
OJ

p

>>

bO
•H

ai
©

hd

Dd

>

rH

•H
O
CO

25

The total elongation of the plants during a comparable
five-month period for 1951 and 1952 is contrasted in Table
Data obtained for 1951 are for three-year-old plants starting
from dormancy, whereas data for 1952 are for the same plants
which had been cut back and flower buds had been removed
for approximately two months.

Total growth as estimated

by total terminal elongation for 1952 indicated three times
the amount of growth obtained in 1951 •

Type of surface

cover did not apparently greatly alter the total amount
of elongation during this period.

Values obtained for

direct radiation and total elongation, however, indicate
a direct correlation of growth with quantity of light*
Table 5 demonstrates the number of flowers produced,
weight per flower, and the total flower weight produced on
all of the plants in each treatment for a five-month period*
Weight per flower and number of flowers were much greater
in the second year and were substantially in the full
radiation than when radiation was reduced.

Differences as

a result of soil cover were not consistently similar*
Experiment Three
As in experiment two, surface cover did not apparently
influence total elongation but total weight of plant material
produced was increased with increased light intensity (Figure
VI).

Reduction of light by

2 percent shading did not

appreciably alter the total elongation or weight of material

01
XI
P
a

o

s

OJ
u\
O'
rH

LA
O'
OJ
OJ

O
X
CO
OJ
CM

c— LA
CM OJ
O0
p O'
CM P

•LA
P
O0'
P

rH
LA
O'
rH

(A
O
CM
CO

CO
x
c—

■—1
vO
O'
vO

O'
0
p
t>-

X X
O' aO
CO O'
vO X

© X OJ
> P LA
P £ O'
P O rH
O £1
? f
at
X
O Ph
SH OS
P, © rH
© C LA
p=;p O'
H H

rLA
OJ
rH
rH

sO
vO
P
rH

0- CM
0“ 'O
O' X
co co

E— c—
CA co
rX
O' vO

1
—1

3 -

C—
fA
CO

O'
CO
CO
CO

O'
0CM
CO

vO
0—
X
CM

CO
O'
1—(

aO
co
vO
1—1
rH

X
C—
p
p
p

la
0

O

CO
vO
CM
P
P

CO
1
—1
OJ
O
P

sD
CO
vO
O'

vO
X
O
X

c^r—
0
X

CM O
0- cO
1A CO
co co

CO cO
P •LA
O' O
co cO

P
•H
Pi
&

P
P
Pi

•3
p
0
&H

GROWTH

AS INFLUENCED

BY LIGHT

INTENSITY

AND

SURFACE

COVER

>
P

CO
C—
co
sD
1—1

o
X
O
■H
U
©
&
oS
U
©
>

o
-p
£h
©

l>LA

nO

p

S

p
cd
©
U

P

©
a
in

p
£
oi
<-l
a
©
ra

x CM

p la
© ^ O'
> 0 rH
p £1
P hi

CM
P

cd

P Pi
© aj

bO © rH
© a LA
<p O'

rH rH

O
U

m
©
g
P
Eh
©

P
P

©
PQ
cm

LINEAR

X

co

Pi
©
>
O
O

©

O

cd

U
Pi
tn

r
P
P

Pt
I*h
&
©

P

P

XI

p
p

0
m

©
P
P
X
£

P
P
O
CQ

©
P
P
X
13

Ph

0
<P
M
£4
©

c

0
p

p

cd

P

©
s
*H
P

p

©

X

O

■6
*H

P
X
©
Ph
1—1
d£>
£h

©
X
cd
XM
P
X
fad
P
X

©
X
©
Xm
>

cd
©
m

P
P
O
CO

27

'— '
M
nCl
-P
d
o
F?
©
t>
•H
CH
*4-1
o

-p
OJ
XA
d
o
O'
H
-p ra
X! S
tsfito
•H d
© bO
5
d
rH «rt
cd
(—1
-p
XA
0
(A
Eh
»-4

u

©
&
O
rH

OJ
■LA
CA
rH

-dvD
XA
-d

vO
vO
C—

vD
GO
rH
CA

■LA
H
O
<A

fA
OJ
rH
(A

-d*
o
CA
OJ

-d- o
Xa
vO
CD -drH H

-d" GO
(A O
CA (A
rH
H

CA
CA

rH
CA
O

OJ
OJ
•
AH

vD
-d9
rH

CA
(A
*
XA
rH

CD
CA
•
XA
H

CA
CA
•
XA
H

-d•
XA
H

OJ
rH
•
vO
rH

CO
—«j
•
XA
rH

-d CA
CA CO
■
•
cA -d"
i
—1 H

-dH

-d-

•
_d

E—
•
OJ

H

rH

XA
vO
OJ

<A
OJ

r-

o
OJ

vO
CA
H

(A
O
OJ

CA
-d■—i

XA
i
—1
rH

J-

vO
CA

CO
CO

-d- -dsO XA

o

O

QUANTITY

AND

QUALITY

OF FLOWERS

m

O
•H
d
©
Pi
cd

d g
© TO
P< d
fciO
-P
—1
£l d i
oO»H XA
CA
•H

d

12

i
—1

O
<4—1

-P
d
©
e
+3
cd
©
d
-p
d
©
p.
m
-P
d
cd
i—I
P.
©
in
O
d
©
©
£
•H
Eh
d
©
-P
-P

©

CM

d XA
© O'
£ |—
O
rH
•h
U

O
d
©
pU

JT*

xa

O'

r

p
©
K
c
c.
©
o
aJ
p.4
GO

cd
OJ
GA

fi
*H
•

ca

t
-P
•rH
d
pH
©
-P
*H

Xi

!s

d
o
•H
-P
aj
■H
■d
cd
d
H
rH
y
EX

c
-p
*H
d
IX
j;

s
-P
•H
d
Ph
rH
*H
O
CO

<D
*P
d

©

Ti
©
,d
©
-p
Xi
&0
•H

rH
*H
O
CO

©
43
•rH
A
3

©
cd

si
m
cd
©
K

i-H
•rH
O
CO

28

INCREMENT OF GROWTH
500

—

400NO
SHADE

GROWTH

IN DECIMETERS

300-

200 I00_
400

—

300

-

42%
SHADE

200

-

100

—

200

—

10 0

65 %
SHADE

—

TIME IN DAYS
Figure VI#

29

produced but reduction by 65 percent greatly .reduced total,
elongation (Figure VI, Table 6),

Weights of roots, tops,

and flowers were greatly reduced by the low level radiation
(65 percent shade), whereas, very little reduction resulted
from ij.2 percent shade (Table 7)»

Number of flowers pro­

duced increased with increased radiation (Table 8)*

Some

of the highest light intensities during this summer period
of growth occurred during June (Figure VII).

Actual per­

centages of reduction of light were found to vary from
month to month and from hour to.hour; therefore, the 65
and \±2 percent refer to the average reduction for the
entire period of the experiment.

Table 9 demonstrates

the quantities of light available to the plants in the
shade treatments as well as full radiation treatments„
Leaf thickness and the depth of the palisade layer
indicate no relation between leaf structure and soil
surface cover.

Positive correlation of leaf thickness

and light intensity was found to be highly significant for
both full radiation and heavy shade treatments (Table 10)•
Depth of the palisade layer of cells in the leaf was found
to vary positively with the light intensity to a significant
degree.

Average depth of upper palisade cells, lower

palisade cells, and whole leaf were found to vary directly
with light intensity.
Intercellular spaces, palisade cells, and spongy
mesophyll cells were much smaller in the leaves exposed to

1A

rH'LA
ft ft

A

BY LIGHT

INTENSITY

AND

SURFACE

COVER

£
©

P

Cd

®

©
GO

Fh

A

AcO

(AO

ft

Fh
-P

©

H

P O
A -p
P O

Ci.

ra

S3
cd
rH
ft—
CM
©A
r
aA
0 rH
Fh

•r

©A
© rH
1 Fh
©
A
Fh O
©p
A o

-P

©

CM C—

bO

A

o

CQ o
p
pK
CM A

AS INFLUENCED
GROWTH

g
xi Fh
f
p O
3
o

u

60
O
©

Fh
©

P
©
6
*H
P
S3
©
u

OO

CM _=jO A-

o
r—

t—

pf CM ft
CM p
cA
P P CM

O
(A
ph
<A
O

co ph

ftft

P
P

p fr— P
CACA AA A CO

<A

CO

A CO

A- P
CAOJ
'LAP
LAO

CO
LA
ft
LA

CMpJ- ft

LA

ALA

rH

CO O

ph
A
CM

hO <4

P

CAP A
AM y Pf

'ft j
—I

CM
LA

CM

A

A<A

O

p p

P o
A fA

CO

O M-

LAcO

O CO CO
Pf-CA A*
—
P ft C
ft A A
ft ft A

fA
LA
■ft

oo

CM

CM

CM(A
pJ*P

A-

CO A

P

Aph o
LALA p

S3

P

Td A
F3
©

rH

TJ

rH

O
•H
Fh
©
PM

l»

["— 0s

3
•"3

P P
A ft

©

pKO

A A CO
LA A LA
LALA P
COCO M-

ft
1
—
I

CO A
'■ft P co
pt A
aLA CM c—

LA

ftft

LAft
O A
A A

3 %

CO LA
CM p f*

p

A
CO
A

A

A

Aft

rp

CM

Apt

co

LA

O

ACM

CM

P

A

oo

H
O

H H

P
CM

O O
iH CM
O pj-

-p

ni

phA

CM
CO

CM A
O rH

P
O
O

ft

P CA

p

&

K

o

a ~a
CM CM

OO

O
A
O
r-

LA

fACA

OvO ft
ft

P la
O pt
A ft A
P CA A
CMCM p t

O
A
O
P

OO
r-r—

AO
CMA

ACM
O pf

3

X

A
H

o o

O A
LALA
O O
P P

rH

P

Fh
ft

Aft

CM

Pt*

O
CA
CM

ft A
O P

<4

ft

o
■H
P
cd

P
-ft

© ©
o o
d aJ
<H
Fh Fh
rj rj
m co

cd A rH
ft P P
Fh O
CO
P
Pm

©
©
XJ
©
A
X3

60

*ri
Pi

© ©
o o
a) d
<H "rH
Fh Fh

3 3
©

©

A H
•H *H
O
ft CO

©
o
d
Fh
Fh

©
tJ 3
d ra
xi
w A
P
tA Fh
> ft
d
©
W

©
o
cd
<1
h
Fh

2
w

p
P
O
CO

A
AA

rH

OJ

31
as
p
o

Sh
©
s
O
H
pH

-P

O
O
m

pl
o

E-!

LA
CM
cA

1
—1
CA
CM
CA

CA
CM
AJ

CA
O
vO

Pt

3

CM C"CO vO
CM ALA (A

CM
GO

pt

CO

CM
LA tA
CA LA
rH rA

ALA
vO
rH

CA sD
rH A-

H O
rH co
O
ACA LA

CA
CA

M3

CO

O
r—

CM vO
I—! LA
■LA CA

lA
O

CM

la

CM
LA

H

rH

rH

3
a-

ca

LA

i—I

0s
vD
aCM

tuC
J
•fH
•H
hO
®
CQ

U
©
>

O
o
©
o
C3
PH
Sh
2
CO

o
LA
3 r—I
A- L A

ca CA
CA pt
A- H
CO \D
rH

©
N
•H
H
*H
P
•H
fp

CM

A-

CO

rH

aO
LA
LA
NO

i
—1 OO

P t

CA
CA

CM

3

O
AJ
O

CO
cA
AJ

■LA

rH

rH

CM
CM

CO

A-

la

CM

LA
LA

P t

rH

3
rH

CA
CM

AO

AJ
CM
LA

CM
CA
LA

P t
LA

cA
CA

CM

U

H
•H
O

O
cA
CA

rH

Pt

©
N
*H
rH
P
«H

U

A-

CM
cA

M3

rH

WEIGHT

-P

Si
bO

aj
•H
IP
aS

©

'G
ai
si
m
P

3
fi-i

&0
•H
Pi

rH

u

•H

P
-r|

to

fc

rH

O

&

o
-P

rH

©
N
•H

IN

GRAMS

OF PLANT MATERIAL PRODUCED BY 2l± BETTER
GROWN MARCH l£ - OCTOBER l£, 19^2

TIMES

ROSE

PLANTS

EH

pt

©

TJ
aS
£GO!
fc*
ai

©

•H

O
C/3

CO

rH

O

CA

32

TABLE 8
YIELD OF FLOWERS AS INFLUENCED BY LIGHT INTENSITY
AND SURFACE COVER
(24 Better Times rose plants per treatment
over a seven-month, period)

Treatment

Percent radiation
100
65

42

Soil cover

356

33 6

191

White HFritM cover

379

328

176

33
Figure VII*

80

LIGHT

INTENSITY

"

60
(Full-radiation)
50

THOUSANDS

OF

FOOT

CANDLES

70

*+o
(Light Shade)
30

20
(Heavy Shade)

10

00
June
TIME

IN

MONTHS

3k
XA

!f\

rH

rH

-P O P
a-p o
<D o
02

XA

U\

rH

rH

• o

•

b£lp P

P

"LA

o.

o
o
o
•k

o
o
o
*k

o
o
o
*k

AJ

XA

O
O
O
•k

O
O
O
•k
o1
—1

o
o
o
•k
AA-p-

FOOT-CANDLE
RECORDS

CO

CA
CA
OJ

© O !»

INTENSITY

AXA

rH
vO
XA

XA "LA

LIGHT

A-

CO
00

hO *
P

CA

o
o
o
CA

CO

©

H P bO

K)

O
O
o

CO

IN

HONRS

<aj

o
o
o
•k
AJ
CA

P

<}

H

P H

vO
CA

o

co

O
O
O

O
O
O

'A
O'

CA

C-

XA

•i
1A

O
O
O
•k
vO
<A

1B-3

hj

O
O
O

O
O
O

O
O

XA

XA
r—t

cd

p

CA
ArH

AJ
XA
CO

rH
AJ
O

o
o
o
•k
rH
i
—I

O
O
O
•»
o
O

■—1
O ©
^-P Cj

•k

•k

•k

o
•k

AJ

"LA

rH

rH

XA
rH

•H O hi
fn -P Cd

&
<!

-P

■S
p

S

O
O
O
•t
c—
tA
rH•k

A-

AJ

C
O
■H
P
cd
•H
T«
cd
H
rH
P

fo

T)
cd
xi

m

p
Xi
w
•H
P

©
P

cd

xl
w

>
cd

©

K

35
TO
TO

<D
n
M
o
•H at
Xl Ft
P o
•<H
at

o
O
•
o
tr\
rH

OvO
•
CO
co
rH

E>rH
•
_dOJ
rH

O'
CO

o

£
O

co
co•

OJ

Pi

OJ

CO

vO

rH

rH

CO
o
o
rH
CO

CO
t—
•

n

©

at
-P

O

SECTIONS

Eh

a

OP LEAP

iH
Fh

©

U
<D

•

D—
•

at

MEASUREMENTS

©

Xi
at

ra

iH
rH
aj

ft Ft
©
*Pi ft
O ft

Xl

P

O
CO
•
1XN

cO

co
OJ

-p

ft

©

Q

O

•rH

P
cd

P
XI

tiO
P)

•H

•H
n
at
Fh
rH

3

ft

©

xf

at

xl
to

-p

■6

©
xf
CS
XJ
in
>

d

©
ra

36

the reduced solar radiation than in leaves exposed to full
radiation (Figure VIII)*

The difference in structure of

leaves grown in full radiation and low solar radiation
is illustrated in a camera lucida drawing (Figure VIII)*
Chlorophyll content was much more intense in the thicker
leaves produced in the highest light intensity#
Total sugars were found to be higher in tissues
obtained from plants grown in full radiation than from
plants grown in light shade.

The heavy shade further

reduced the total sugars (Table 11).

Sugars increased

greatly on June 13 and during the following night rapidly
decreased in leaf and stem tissues.

During each daylight

period total sugars continued to increase and to decrease
during the dark period (Figure XX)#

At the end of the

three-day period of high radiation, however, the tissues
contained a much larger percentage of total sugars than
at the beginning of the three-day period#

The increments

of increase of total sugars were nearly equal in the
three light treatments*

The percentage of ash on a dry

weight basis decreased during the daylight and increased
during the dark period#

37

Figure VIII,

Camera lucida drawings of crcss-sections
of leaves from plants grown in full sunlight
(upper drawing) and 65 percent reduction of
sunlight (lower drawing).

38
*

XA

'— '
(D
d
w
to
•H
-P

€
P
ha

s

l-i
erf
©
.H
1-i
O
co
®
r“1
D-

§

to

o

SO
O
o

XA

to
C\J
*
rO

O
O
•
vD

m
S■
PL,

to
XA
•
tO

CO
vO
•
xa

O
O
OJ
•>
-d
0-

o
o

rH
»
-d

c—
0s
o
to

CO
GO
o
XA

rH
C—
•
vO

OJ

en
rH
CD
§
3
ha

•
S•

o

00
r-

<1

O
O'
•
OJ

GO
•
vO

CO
to
•
OJ

•
S«

rH -do
3•
•

pm

-d- vO

to
CO
•
to

*
E•
<rf

co
OJ
•
OJ

XA
vO
•
yD

o
o

-vO
•k
i-H
n0

OJ

OJ
i—1

O

€
pj
3
ha

vO
■k
CO
-d-

SH
&o
1
c
©
Eh

U
©
>
S3
H

(J

£3
O
•H
43
erf
•/—i
d
erf
Sh
H
rH
y
[il

4d
ta
<

•
oi
SH
a
*
d
o
i
•
43
Ph

o
o

OJ
rH
•
to

o
0•
XA

-d
vO
•
OJ

XA
-d*
«
nO

.d'
cO
•
OJ

to
Ad
XA

r—

CA
•
OJ

OJ
-d
•
vO

o

o

OJ
CO
o
XA

_d*

XA
•

(O
•
vO

co
vO
•
vO

o

o
o

-d*
•k
to
OJ

OJ
«
to

CO
v£>
•
rH

<o
-d
•
vO

o
o
XA
•

o

u
erf
bO
d
n

-P
a

o
oo

O
o
rH
•k
r—
OJ

vO
•k
c—
CVJ

ft

©
-P
to
d
S3
erf

XA
r•
-d-

•
a
m
<

_d
rH

PERCENTAGE

TOTAL

SUGARS

AND ASH

IN RELATION

TO LIGHT

INTENSITY-

rH
©
£3
P
*”3

•
Oi

•
to

43
u
©
>
S3
H

43
©
Aj

in
«
d
O
I
o
43

OJ
ft
rH
OJ

O
O
d
•k
OJ
OJ

tH
erf
bO
d
©
43
Sh
©
>
S3
H

ro

i»
I
dj

o
o

OJ
•k
0rH

®
d
<rf
43
M

©
d
ai
43
©

43
■4
bO
•H
id

>
erf
©
tn

*
01
SH
tn
•
d

o

43

ro

<*

©
•H

erf
42

O
O
to
o
OJ
H

O'
rH

u
erf
bO
d
to

o
o

i
•
43
tL

S3
©
!>
O
S3
O
d
©
n
©
©
SH
ex
M
©
d
£3
erf
U
erf
bO
d
©
43
Sh
©
>
S3
*H
01
©
d
©
43
erf
<d
d
o
H
erf
O

39
Figure IX.

VARIATION IN TOTAL SUGARS*

5.00

*+.75
^.50
^.25
W.oo

3.75
Full-Radia ti on

3.50

% TOTAL

SUGAR

3.25
3.00
2.75
eavv Shade

2.50
2.25

2.00
1.75
1.50
1.25

I

f

am

pm
June 13

I
am
June

i
pm
1^

1
am

pm
June 15

♦Calculated as invert sugar.

DISCUSSION
Reduction of total plant weight and number and quality
of flowers resulted from shading rose plants.

These results

are similar to the findings of Batson in 1933> who examined
numerous plants grown In reduced light conditions.

Shading

of plants with cloth during the summer months without
additional shading applied to greenhouse glass resulted
in high air temperatures and low available solar radiation.
An extreme reduction in light intensity combined with high
temperature might be expected to greatly reduce carbohydrate
synthesis and indirectly retard growth.

Pronounced reduction

in accumulated carbohydrates might occur in plants shaded
by cloth during early morning hours, evening hours, and
during cloudy periods.

Kamp (I9J4.8 ) has reported a reduction

in carbohydrate of plants as a result of shading and Weinard
and Decker (1930) found the quality and yield of greenhouse
roses to be reduced as a result of low light intensity
available to certain plants in a greenhouse bench.

A

reduction of carbohydrates and consequently a reduction
in growth might result during periods of high temperature
and it would become severe under conditions of extremely
low light intensity.
Surface covers which Increased the amount of reflected
light yielded increases in growth of small plants only when

ia

solar radiation was extremely high.

Intensity of reflected

light decreased rapidly as a result of decreased incident
light and decreased progressively as surface cover became
shaded by foliage of developing plants.

Such measureable

decreases in reflected light resulting from increase in
plant size were noted immediately after the plants began
to develop.

Reflected light continued to decrease until

the Intensity was low and of limited physiological Import­
ance,

Salisbury in 1918 recorded light intensity as low

as 0,16 percent under lower leaves of woody plants.

Combes

(1910) reported the optimum light intensity for the pro­
duction of dry matter in plants to increase with increasing
age and consequent size of plants.
Increases in total weight of plant material with
increased light intensity was consistent in all experiments.
As plants grew larger and the density of foliage was
greater, the magnitude of differences was increased by the
additional months of growth.

Increases as a result of

reflected light were variable and of less magnitude in the
shaded treatments than in those of full radiation.

Light

recordings revealed very low light intensities donated by
reflected light as a result of shade treatments combined
with the additional obstruction from heavier foliage,
Growth differences obtained as a result of different
light intensities greatly exceed those differences in size

kz

obtained as a result of alteration of surface cover*

Very

little light was available to be reflected, regardless of
surface cover and did not greatly influence total growth
over a long period of time*
The second year1s growth was much greater than that of
the first year as a result of removal of flower buds during
the summer*
hydrates*

Such removal was intended to conserve carbo­
Likewise the second year's growth was increased

by further root development and greater leaf area*

Number

and quality of flowers were increased during the second
year which suggested the difficulty of directly correlating
growth of perennial plants with data of a physical nature
unless age and previous treatment were well recorded and
interpreted*
Reflected light did not appear to be influential in
producing higher yields.

It was possible that with woody

plants or plants which greatly shade the soil surface,
reflected light could not become available in intensities
effective for Increasing growth.

Reduction of the total

direct solar radiation to 58 percent did not greatly reduce
growth or flower production.

Reduction to 35 percent

affected quality and quantity of plant material severely.
Reduction to 58 percent was not as significant in its effect
upon plant growth.

Consequently, efficiency of utilization

of solar radiation as indicated by bulk of growth during the

1+3

period of this experiment must have reached a critical
point between 35 and 58 percent of full solar radiation,
for the existing temperature.

It was probable that

radiation in excess of 58 percent of the total was bene­
ficial but with limited efficacy.

Reduction of light to

the extent of approaching the 65 percent level, regardless
of the greenhouse temperature, should result in sizeable
reduction in total growth of the rose plants.

Reduction

of light to the 20 percent level resulted in very little
growth of plants.
Light records were not compared with those available
from the local weather bureau because different types of
receiving bodies having variable linearity, range of
sensitivity, and fatigue factors were used In this investi­
gation,

Greenhouse glass received an application of

shading compound during the period of high radiation.
Percentage reduction of light was found to vary constantly
and, as reported by Gray (193l+)> various quantities of
diffused light altered the amount of reduction resulting
from shading.

Cords and threads of textiles have depth

and width which make possible great difference of amount
of light passing through the openings depending on angles
of incidence.

Ends of greenhouses caused additional shading

on some plants in early morning and in late evening.

All of

these factors allow for only relatively accurate solar
radiation recordings In greenhouses regardless of the

kk

quality of available equipment.

Only averages of percentage

reductions and totals of radiation were presented.
Studies of leaf anatomy verify findings of Pickett
(1938)5 Hanson (1917)5 and Penfound (1931) in regard to
modifications of leaves by varying light intensities#

It

is felt that increased vigor and rate of growth as a result
of sufficient light produced leaves which were substantially
thicker, layers of palisade cells which were deeper, and
spongy mesophyll which was much more compact.

Leaf

structure, therefore appeared to offer some indication of
the proximity of light intensity to the cardinal points.
High radiation, in addition to facilitating the production
of the greatest amount of plant material, facilitated the
development of much thicker leaves than did a reduction to
35 percent of total radiation.

Results obtained with less

than 20 percent full solar radiation in which plants
showed little suitable growth, indicated a light intensity
near the minimum.

It was often below this level that

greenhouse rose plants during the winter months under
heavy shading exhibited growth difficulties during cloudy
days.
percentage of total sugar Increased measureably in
leaves and stems of rose plants at high light intensities
and temperatures.

Maximum light intensity for photosynthesis

and accumulation of carbohydrates were apparently not exceeded

for any length of time during periods of highest radiation
during this investigation.

Efficient utilization of light

apparently decreased at extremely high light intensities
but not to an extreme degree.

Translocation, utilization

in growth, or respiration of sugars appeared to take place
rapidly after one daylight period of low solar radiation
was followed by one of high solar radiation.

Such vari­

ations in sugar content were not as obvious after one or
two days of high radiation.

On a percentage dry weight

basis the ash content decreased as sugars content increased*
Such analyses of tissue for invert sugar served as a useful
technique for the study of growth and carbohydrate accumu­
lation in plants*

SUMMARY”

Three plantings of roses were made to study quanti­
tative and qualitative effects of light intensity on the
growth of Better Times roses.

Growth measured by elongation

and fresh weights of all plant material produced was
correlated to light intensity by means of recording light
intensity over plants growing in shade houses constructed
of cloth and designed to allow 20, 3£> and 5>8 percent
incident radiation to be available.

Total radiation as

well as the reduced radiations was measured by means of a
Speedomax recorder.

Soil surface was covered with a highly

reflective 11frit", with a less reflective "frit", and with
soil.
Carbohydrate analyses were made of tissue subjected
to three levels of radiation.

Sections of leaves were

collected for an anatomical study of rose leaf development
resulting from various quantities of light.
Total growth of the rose plants was reduced by
decreases in light intensity.

Reduction to 20 percent

total solar radiation reduced growth to an extreme degree,
and appeared to be near the minimum light intensity for
growth.

Light of the magnitude of f>8 percent of full

radiation allowed growth to be only slightly reduced.

k-7

Judging from growth produced it appeared as if plants
growing in £8 percent radiation had been supplied with
almost as much light as was ideal for maximum growth*
Any reduction of light below

percent of the total

radiation resulted in rather sharp decrease in total growth*
Surface covers which increase the amount of reflected
light seldom increased plant growth.

Plant growth response

from such indirect light was noted when radiation was
extremely high and then only if plants were very small*
This finding was thought to be related directly to the
amount of shading of surfaces by plant foliage.
Carbohydrate analysis revealed a great increase in
total sugars in leaf and stem tissue during periods of
intense heat and extremely high radiation*

Translocation,

respiration or utilization of carbohydrates were found to
occur in great quantities after periods of dark or cloudy
weather.
Leaf structure was greatly modified by the intensity
of light available to various plants.

Heavy shading

resulted in the development of very thin leaves with
palisade cells of much less depth than those of leaves
subjected to high radiation; total chlorophyll content
appeared to be much greater in leaves obtained from these
plants.

REFERENCES CITED
Adams, J. 1925* Some further experiments on the relation
of light to growth. Amer. J. Bot, 12:398-1*12.
Aldrich, L. G. 1919* The reflecting power of clouds.
Smithsonian Misc. Coll. #2530, Vol. 69.
Arthur, J. M. and Stewart, W. D. 1931* Plant growth under
shading cloth. Amer. J. Bot. 18:897.
Baird, K. W. 1923* The measurement of light for ecological
purposes. J. Ecol. 11:1*9-63.
Bates, C. S. and Roeser, J. 1928. Light intensity required
for growth of conifer seedlings. Amer. J . Bot. l5:l85-19l**
Batson, F. S. 1933* Studies of the effect of cheesecloth
enclosures on the flower production, underground develop­
ment, and rate of transpiration of flower crops. Proc.
Amer. Soc. Hort. Sci. 30:580-582.
Blackman, F. F. 1905.
Bot. 19:281-295*

Optima and limiting factors.

Ann.

and Matthaei, G. L. C. 1905. On vegetative
assimilation and respiration. Proc. Roy. Soc. London
B76:1*02-1*60.
Blackman, G, E. and Templeman, W. G. 19l*0. The interaction
of light intensity and nitrogen supply in the growth
and metabolism of grasses and clover (Trifolium repens)
IV. The relation of light Intensity and nitrogen supply
to the protein metabolism on the leaves of grasses.
Ann. Bot. n.s. l*:533-587*
Bouyoucos, G. J. 1950. A practical soil moisture meter as
a scientific guide to irrigation practices. Agron. J.

!*2:10!*-107 •
Boysen-Jensep, P. and Muller, D. 1929. ^ie maximale Ausbeute
und der Tagliche Verlauf der Kohlensaure assimilation.
Jahrb. f. wiss. Bot. 70:1*93-502.
Broyer, T. C. and Hoagland, D, R. 19l*3* Metabolic activities
of roots and their bearing on the relationship of upward
movement of salts and water In plants. Amer. J. Bot. 30:
261-273*

k-9

Burkholder, p. r, 1938. The role of light in the life of
plants. Bot. Rev. 2:1-52, 97-168.
Burns, G. R, 1933* Photosynthesis in various portions of
the spectrum* Plant Physiol. 8:21+7-262.
Burns, S. p. 1923* Measurements of solar radiation energy
in plant habitats. Ecology 1+:189-195*
Christopher, E. P. 1931+* The intensity of light striking
leaves of apple trees at different times of day. Proc,
Amer. Soc. Eort. Sci. 32:86-92.
Clements, E. S* 1901+* The relation of leaf structures to
physical factors. Trans. Amer. Micro. Soc. 26:19-102.
Clements, P. E. and Long, P. L. 193^* Factors in elongation
and expansion under reduced light intensity. Plant
Physiol. 9:165-172.
Clum, H. H. 1926. The effect of transpiration and environ­
mental factors on leaf temperatures. I. Transoiration.
Amer. J. Bot. 13:191^230.
Combes, R. 1910. Determination des intensites lumineuses
optima, Ann. Sci. Nat. Bot. 11 (IX):75*
Cormack, R. G. H. 1950.
Agron. J. 1+2 (7):

A study of leaf thickness in wheat.

Crabb, G. A., Jr. 1950. Solar radiation investigations in
Michigan. Mich. State Coll. Tech. Bull. 222*
Darwin, P. 1911+. The effects of light on the transpiration
of leaves. Proc. Roy. Soc. London B87:281-299.
Davis, A. R. and Hoagland, D. R. 1928. Further experiments
of plants in controlled environment. I. Relation of light
intensity and exposure time to yield. II. The interrelationshio of temperature and light. Amer. J. Bot. 15:

621+.
Deats, M. E. 1925* The effect on plants of the increase and
decrease of the period of illumination over that of the
normal day period. Amer. J. Bot. 12:381+-393«
DeVore, L. 1938. Methods of measuring radiation for bio­
logical purposes. Pa. State Coll. Bull. 359*
Dinger, J. E. 191+1* Ttle absorption of radiant energy in
plants. Iowa State Coll. J. Sci. l6;l|i+-i+5*

50

Duggar, B. M. 1936# Biological effects of radiation.
York: McGraw-Hill Book Company*

New

Emerson, R, 1929* Photosynthesis as a function of light
intensity and of temperature with different concentra­
tions of chlorophyll. J. Gen. physiol. 12:623-639*
^ and Lewis, C. M. 1939* Factors influencing
the efficiency of photosynthesis* Amer. J. Bot. 26:
608-822.
~ --Fischer, C. W. and Kofranek, A. M« 1949* Bottom break
production of rose plants as influenced by plot location
in the greenhouse. Proc. Amer. Soc. Hort* Sci. 53:501-502.
Funke, G* E. 1931* On the influence of light of different
wavelengths on the growth of plants. Rec. Trav. Bot*
Neerl. 28:431-485.
Garner, W. W. and Allard, H. A. 1920* Effect of the
relative length of day and night and other factors of
the environment on growth and reproduction in plants#
J. Agr. Res. 18:553-606.
Gast, P. R. 1937* Studies of the development of conifers
in raw humus III: The growth of scots pine (pinus
sylvestris) seedlings in pot cultures of different soils
under varied radiation intensities. Medd. Skogsoforsokanst Stockh. 29:582-587.
Gourley, J. H. and nightingale, G, T. 1921. The effects
of shading some horticultural plants. N. H. Tech. Bull. 18.
Gray, G, F. 1934* Relation of light intensity to fruit
setting in the sour cherry, Mich. State Coll. Tech.
Bull. 136.
Hamner, K. C. and Bonner, J. F. 1939* photoperiodism in
relation to hormones as factors in floral initiation
and development. Bot. Gaz* 100:388-431.
Hanson, H. C. 1917. Leaf structure as related to environ­
ment. Amer. J. Bot. 4:533-560,
Harder, R* 1921. Eritische versuche zu Blackmans Theory
der "begrenzenden Factoren" bei der Kohlensaureassimilation. Jahrb. f. wiss. Bot. 60:531-571.
Harvey, R, B. 1922. Growth of plants in artificial light.
Bot, Gaz. 74:447-451.

51

Harvey, R, B. and Hedricks, E. 1923* Growth of plants in
artificial light. Bot. Gaz, 77:330-334*
Heinicke, A. J. and Hoffman, M. B, 1933# The rate of photo­
synthesis of apple leaves under natural conditions, Part I.
Cornell Univ. Agr. Exp. Sta. Bull. £77,
Hemphill, D. D. and Mumeek, A. E. 1950. Light and tomato
yields. Proc. Amer. Soc. Hort. Sci. 55:346-350.
Holley, W. D. 1942. The effect of light intensity on the
photosynthetic efficiency of carnation varieties. Proc,
Amer. Soc. Hort. Sci. 4°:569-572.
Howland, J. E. 1946* The rate of photosynthesis of green­
house roses. Proc. Amer. Soc. Hort. Sci. 47:473-481*
Huhbell, D. S. 1934* Causes of blind wood in roses.
Physiol. 9:261-282.

Plant

Johnston, E. S. 1938, Plant growth in relation to wave
length balance. Smithsonian Inst. Misc. Coll. 97*
Publ. #3446.
Kamp, J. R. 194$• The incidence of blindness in the Better
Times rose. Proc. Amer. Soc. Hort. Sci. 52:490-500.
Kiplinger, D. C. 1939.
I nc. Bull. 18*3-6.

Photosynthesis of roses,

Roses

Kohl, H. C., Fosler, G, M. and Weinard, P. F. 1949. The
effect of several soil temperatures on flower production
in roses. Proc. Amer. Soc. Hort. Sci. 54:491-494*
Kraybill, H. R. 1923. Effects of shading and ringing upon
the chemical composition of apple and peach trees.
N. H. Agr. Exp. Sta* Tech. Bull. 23.
Kvapil, K. and Nemec, A. 1928. Uber den Einfluss des
Lichtes auf e’inige physikalische und chemische Bftdeneigenschaften in reinen Nadel - und Laubholzbestanden
sowie in gemischten Bestanden. Abstract in Bot. Centralbl. 153:473*
Laurens, H. 1933. The physiological effects of radiant
energy. New YorFT"Chemical Catalogue Company.
Laurie, A. and Witt, D. J. 1941* Effect of some spray
materials on the apparent photosynthetic rate of
greenhouse roses. Proc. Amer. Soc. Hort♦ Sci. 38:655-657.

52

Lubimenko, W* 1908. Production de la substance s4che et
de la chlorophylls chez les v4g&taux supferieurs aux
diff&rentes intensit^s lumineuses. Ann- Sci. Nat. Bot*
IX, 7:321-415.---------------------- --- --- --- --McCool, M. M. 1935* Effect of light intensity on the
manganese content of plants. Contrib. Boyce Thompson
Inst. 7:4-27-437*
------- ------------ ---Mitchell, H. L* 1936. The effect of varied solar radiation
upon the growth, development, and nutrient content of
white pine seedlings grown under nursery conditions*
Black Forest Papers 1:16-22*
Muncie, F, W. 1917. The use of commercial fertilizers in
growing roses. 111. Agr. Exp. Sta. Bull. 196*
Nightingale, G. T« 1933* Light in relation to growth and
chemical composition of some horticultural plants. Proc*
Amer. Soc. Hort. Sci. 19:18-29*
penfound, W. T« 1932. Plant anatomy as conditioned by
light intensity and soil moisture. Amer. J. Bot. 19:
530-546.
~
Pfeiffer, N. E. 1928. Anatomical study of plants grown
under glass transmitting light of various ranges of
wave lengths. Bot. Gaz. 85:427-436*
Pickett, W. F. 1934* Photosynthetic activity and internal
structure of apple leaves are correlated. Proc. Amer*
Soc. Hort. Sci. 32:81-85*
» 1938. The relationship between the internal
structure and photosynthetic behavior of apple leaves.
Kansas Agr. Exp. Sta. Tech. Bull. 42*
* and Kenworthy, A. L. 1939. The relationship
between structure, chlorophyll content, and photosynthesis
in apple leaves. Proc. Amer. Soc. Hort. Sci. 37:371-373*
• 1942. The Influence of some spray materials
on the internal structure of apple leaves. Kansas Agr.
Exp. Sta. Tech. Bull. 53*
poesch, G. H. 1931. Studies of photoperiodism of the
chrysanthemum. Proc. Amer. Soc. Hort. Sci. 28:309-392*
Popp, H.
W. 1926a. A physiological study of the effect of
light
of various ranges of wave length on the growth of
plants. Amer. J. Bot. 13:706-736*

53

Popp* H. W. 1926 b. Effect of light intensity on growth of
soy beans and its relation to the autocatalyst theory
of growth. Bot. Gaz. 82:306-319*
Porter, A. E. 1938* Effect of light intensity on the photo­
synthetic efficiency of tomato plants. Th e sTs, Mi chi g an
State College,
Post, K, and Nixon, M. W. 1939. An apparatus for the
continuous recording of light intensity in foot candles
(Graphic Light Meter), proc. Amer. Soc. Hort. Sci. 37:278.
and Howland, J, E. 1946* The influence of nitrate
level and light intensity on the growth and production
of greenhouse roses. Proc. Amer. Soc. Hort. Sci. 47:

446-450.

:

Ratsek, J. C. 1944* The effect of temperature on bloom
color of roses. Proc. Amer. Soc. Hort. Sci. 44:549-551.
E. 1913* Energie assimilatrice chez les plantes
cultiv6es sans diffirents &clairement* Ann. Sci. Nat,
Bot. IX, 17:1-110.

R o s 4,

Salisbury, E. J. 1918. The oak-hornbean woods of Hertford­
shire. J. Ecol. 4:83-117*
Sayre, J. D. 1928, The development of chlorophyll in
seedlings in different ranges of wave lengths of light.
Plant Physiol. 3:71-77*
Scarth, G. W. 1927,
regulatory role.

Stomatal movement: its regulation and
Protoplasm 2:498-511.

Shull, C. H. 1936*
Rate of adjustment of leaf temperature
to incident energy. Plant Physiol. Il:l8l-l88.
Shanks, J. B. and Laurie, A. 1949. Rose root studies: Some
effects of soil temperature. Proc. Amer. Soc. Hort. Sci.
54:495-499*
Shantz, H. L. 1913*
Effects of artificial shading on plant
growth in Louisiana, U. S^. Dept. Agr., Bur. Plant Ind.
Bull. 279*
Shirley, H. L. 1929. The Influence of light Intensity and
light quality upon the growth of plants. Amer. J. Bot.
16:354-390.
_____________ , 1931* Light sources and light measurements.
Plant Physiol. 6:447-466*

54

Shirley, H. L. 1935® Light as an ecological factor and its
measurement, Bot. Rev, 1:355-381®
Steinbauer, G. p, 1932. Growth of tree seedlings in
relation to light intensity and concentration of nutrient
solution. Plant Physiol. 7:74-2-744®
Street, 0. E. 1934® Carbohydrate-nitrogen and base element
relationships of peas grown in water culture under
various light exposures. Plant Physiol. 9i301-322,
Wallace, R. H. and Clum, H. H. 1938.
Amer. J. Bot. 25:83-97,

Leaf temperatures,

Weinard, F. F. and Decker, S. W. 1930* Yield and quality
of roses and carnations as affected by position on bench.
Proc. Amer. Soc. Hort. Sci. 27:454-456.
Went, F. W. 1941* Effects of light on stem and leaf growth.
Amer. J. Bot. 28:83-95®
White, H. L, 1905® The interaction of factors in the growth
of Lemna. Ann. Bot. XI, 1:623-647•
Withrow, R. B. 1943® Radiant energy nomenclature.
Physiol. l8:476-i|87®

Plant