THE EFFECT OF 50“. TEMPERATURE UPON THE
GROWTH OF CARNATION {DIANTHUS CARYOPHYLLUS. L)

EASTER LILY (“HUM LONGIFLORUM, THUNB} AND
GERANIUM {PEARGONNM HORTORUM, BAILEY]

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Michigan State

University

ABSTRACT

THE EFFECT OF SOIL TEMPERATURE UPON THE GROWTH OF
CARNATION (DIATHUS CARYOPHYLLUS, L.)

EASTER LILY (LILIUM LONGIFLORUS, THUNB) AND GERANIUM
(PELARGONIUM HORTORUM BAILEY)

By Changhu Peng

Body of Abstract
Submitted to
the School for Advanced Graduate Studies of
Michigan State University

in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Horticulture

1963

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Changhu Pengo

This study was undertaken to study the effect of
soil temperatures of M0°, 60°, and 80° F, on growth of car-

nation (Dianthus caryophyllus, L.), Easter lily (Lilium

 

longiflorum, Thumb), and Geranium (Pelargonium hortorum,

 

 

Bailey) in Plant Science Greenhouse, Michigan State University.
Growth was measured as dry weight, number of leaves,

and days to flowering. In addition, measurements were made

on size of flower, number and total growth of side shoots

in carnation; days to emergence, size of flower, number of

flower in Easter lily; leaf area, number of leaves, number

of flower clusters, number of floret per flower in Geranium.
Results show that in carnation plants, no significant

differences were found among treatments involving flowering

data and root dry weight. The only difference was that HOP F

treated plants were inferior to others in number and total

,growth of side shoots and stem length.

In Easter lily, uo0 F soil temperature delayed emer-

_gence of shoots, the plants were unable to bloom by the end

of the experiment. No significant difference was found
between 60° and 80° soil temperature treatment as regard to
days to emergence, but plants in 80° treatment flowered 6.6
days earlier than 60° treatment.

In Geranium, besides flowering date, plants in 40° F

treatment were inferior to those in 80° and 60° treatments in

Changhu Peng

every reSpect. 60° F soil temperature was considered as

the best for growing geranium.

THE EFFECT OF SOIL TEMPERATURE UPON THE GROWTH OF
CARNATION (DIANTHUS CARYOPHYLLUS, L.)

EASTER LILY (LILIUM LONGIFLORUM, THUNB) AND GERANIUM
(PELARGONIUM HORTORUM BAILEY)

By
Changhu Peng

A THESIS
Submitted to
the School for Advanced Graduate Studies of
Michigan State University

in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Horticulture

1963

ACKNOWLEDGMENTS

The author extends grateful appreciation to Dr. Richard
F. Stinson for his suggestions and criticisms throughout the
duration of this investigation and for his constant encour-
agement during the program.

Further acknowledgment is extended to Dr. Richard
Lindstrom and Dr. Henry D. Foth for their invaluable criti-
cism in the preparation of the thesis. Special thanks are
extended to Dr. Donald Henry Dewey for lending thermometers
to record the air temperature of the greenhouse; Dr. Arthur
Edwin Mitchell for teaching methods of measuring leaf area,
and Dr. Hubert McClure Brown for solving problems of data
analysis.

The author also wishes to acknowledge the devotion
and sympathetic understanding of his wife, without which the

present investigation would not have been undertaken.

ii

TABLE OF CONTENTS

ACKNOWLEDGMENTS. . . . . . . . . . . . . . . . .
LIST OF TABLES O O O 0 O O O O O O 0 O O O O O 0

INTRODUCTION 0 O O O O O O O O O O O O O O O O 0

LITERATURE REVIEW. . . . . . . . . . . . . . . .

Air Temperature and Soil Temperature and

Plant Growth . . . . . . . . . . . . .
Factors Influencing Soil Temperature. . .
Soil Temperature and Plant Growth . . . .
Soil Temperature and Water. . . . . . . .
Soil Temperature and Nutrients. . . . . . . .
Optimum Soil and Air Temperature for Economic

Plants (Table) 0 O O O O O O O O O O O O 0

MATERIALS AND METHODS . . . . . . . . . . . . .
RESULTS . . . . . . . . . . . . . . . . . . . .
DISCUSSION . . . . . . . . . . . . . . . . . . .
SUMMARY. . . . . . . . . . . . . . . . . . . . .
BIBLIOGRAPHY . . . . . . . . . . . . . . . . . .

APPENDIX 0 O O O O O O O O O O O O O O O O O O 0

iii

Page
ii

iv

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LIST OF TABLES

Table Page

I. Growth of Carnation as Related to Soil
Temperatureooooooo0.00.0000. 38

II. Growth of Easter Lily as Related to Soil
Temperature 0 O O O O O O O O O O O O O O O 0 ”0

III. Growth of Geranium as Related to Soil
Temperature . . . . . . . . . . . . . . . . . 42

iv

INTRODUCTION

Among many environmental factors influencing plant
growth, soil temperature is an important one. In natural
conditions, the seasonal changes in soil temperature deter-
mine to a certain extent the germination of seeds, emergence
and growth of plants. Some cultural practices such as time
of seeding, mulching, shading, use of compost in hot bed are
all related to soil temperature.

Soil temperature is also important in greenhouse
plant growing, for a proPer soil temperature may have a
favorable influence on the growth, time of harvesting, pro-
duction and quality of plants as well as fuel consumption.
In the case of Michigan, because of a short growing season,
commercial flower production is mainly confined to green-
house culture. So it is important to study the effects of
soil temperature on flowering plants.

The present work was designed to study the effects
of different soil temperatures upon the growth of several
flowering plants under greenhouse conditions, in order to
establish the limits of appropriate soil temperature range
for flowering plants. It is hOped that this work may have

some help to Michigan flower growers.

LITERATURE REVIEW

Air temperature and soil temperature and plant growth

 

Only limited researches have been done on the effect
of both air and soil temperature upon plant growth.

For forage crops, under conditions of equal soil and
air temperatures, Brown (13) found that the optimum tempera-
ture for root and rhizome production in Canada bluegrass was
10° c, Kentucky bluegrass, 15.6° c; and orchard grass, 21° c.
For Bermuda grass, growth increased with rising temperature
up to 37.8° c, the highest temperature employed. Using
plants in growth chambers with controlled temperature altera-
tions, Sprague (7%), found at the end of a 6-week period that
the best root growth in Ladino clover was at n.u° c to 12.8° c;
in Kentucky bluegrass, orchard grass, meadow fescue, brome
grass, colonial bluegrass, and timothy, 12.8° to 21° c; and
Sudan grass, 21° to 29.u° c.

Bushnell (16) studied potato growth in a controlled
temperature chamber in which the air temperature and soil
temperature were maintained the same. He found the average
weight of tubers per plant 6 weeks after emergence was 20.9
’gram at 20° c, 5.0 gram at 23° c, and 1.6gram at 26° c,
while no tubers appeared at 29° c. The root growth was not

appreciably reduced at 23° c or 26° c, but somewhat nudified

at 29° c.
Calvert A. (17) grew tomato plants in greenhouses
in 1953 and 195a. The air temperature and soil temperature

used were as follows:

Year Air Temperature Soil Temperature

Day Night
1953 60° F 52° F 61.u° F

60° F 52° F 56.8° F
1953 65° F 57° F 6H.u° F

65° F 57° F 60.9° F
195% 63° F 58° F 65.7° F

63° F 58° F 58.7° F
195a 60° F 52° F 65.6° F

60° F 52° F 56.5° F

Concluded that "when the control soil temperature was 56°-
57° F at planting out time, increases of from 5° F to 9° F
produced no significant increases in yields of ripe fruit,
either for early or for total crop,” and "reduction in air
temperature produced marked decreases in early yield, but had
no clear effect on the total crop."

Hellmers, Henry (#0) using redwood seedlings of 6
weeks and 20 weeks old maintained soil temperatures of 8° c,
18° c, 28° c and two sets of air temperatures of 30° c day
temperature (8 hours) and 2u° c night (16 hours), and 17° c
day temperature and 11° c night temperature. A 16 hour‘
photoperiod was obtained through supplemental lighting in
the morning and evening. He found the growth response of

redwood seedlings to air and soil temperature depends to some

extent upon their age or size. High air temperature stimu-
lated top growth with each of the three soil temperatures.
Low air temperature combined with warm soils stimulated root
growth. A high air temperature effect tended to counter-
balance a cool soil effect and vice versa. Roots grown in
18° c soil temperature appeared to be the healthiest, but

in case of 20 week seedlings, the dry weights of the roots
were not significantly different among treatments.

Nelson (56) studied the growth of hemp (cannabis
satious), using seedlings transplanted to gravel cultures 11
days after germination, having tOps at 15° c with roots at
15° c and 30° c, and teps at 30° c with roots at 15° c and
30° c. Differences in growth began to appear after u weeks
and became marked after 7 weeks. At an air temperature of
15° c, the plants grown in the 30° soil produced a large
number of leaves, thicker stems, and greater total dry weight
of t0ps than those in 15° soil. There was little difference,
however, in the size of the leaves or the height of plants
grown at these two soil temperatures. The higher air temper-
ature of 30° c was less favorable for the deve10pment of the
hemp, and the growth differences caused by soil temperature,
though smaller, reflected the same trend.

Went, F. W. (83) found that at variations in root
temperatures between 32.5° c and 15.5° c the growth rate of
tomatoes was determined entirely by the temperature at which
the t0ps were kept.

In summary, it is obvious that both air temperature

and soil temperature affect the growth of plants, and these

varied with kinds, varieties and age of plants.

Factors influencing soil temperature. According to
S. J. Richard's review (62), among many factors influencing
soil temperatures, radiation from the sun is the primary
heat source. The rate at which radiant energy reaches the
earths atmOSphere from the sun (solar constant) has the value
1.90 calories per minute per square centimeter normal to the
direction of the radiation, absorption by the earth's atmos-
phere, however, causes large variations in the rate at which
radiant energy reaches the soil. Another factor influencing
soil temperature is the loss that heat energy from the soil.
The net rate of heat gain or loss determines whether the
soil temperature is being raised or lowered. Radiation
from the soil surface is an effective way of losing heat to
the atmosPhere. The surface characteristics of soils vary
greatly. Brooks (12) lists data to show that the soils for
Which data are available limit long-wave radiations at rates
varying between 0.” and 0.5 of a black body surface. Al-
though the instaneous rate of long wave radiation is much
smaller than the peak value of solar radiation. Long-wave
radiation is still important, since it operates continuously
and not just during the daylight hours. Assuming a surface
emissivity of 0.5 and an average temperature of 30° c, the
amount of heat radiated from one square centimeter of soil
surface in 2a hours amounts to approximately 500 calories.
Water vapor, carbon dioxide, and Ozone in the atmosPhere
are good absorbers of radiation in the range of wave lengths

that comes from the soil surface. These absorbers in turn

become emitters of radiation as well. The intensity of solar
radiation per unit of surface area is proportional to the
cosine of the angle between the direction of radiation normal
to the surface. This relation accounts for the continual
decimal change in radiation intensity as the sun's position
changes, and is also one of the factors in the soil temperature
relations, since the angle indicated above depends on the
latitude and the lepe of the soil surface. Shade and insula-
tion are also important factors in influencing soil tempera-
tures, largely to the extent they affect the exchange of heat
at the soil surface by radiation. Evaporation of water from
a soil surface also effects soil temperature. For every

gram of water evaporating from the soil surface, a quantity
of heat energy equivalent to approximately 580 calories is
lost by the soil. When the soil surface is wet, evaporation
is dependent on vapor-pressure gradients and wind velocity

in the air just above the surface, as well as the amount of
radiant heat energy available. When the soil surface is

very dry, the rate at which water evaporates from the soil
surface depends on the rate at which water is transported

from the lower layers of the soil to the surface. Convection
is another process whereby heat is transferred to or away

from the soil surface. The direction and rate of heat trans-
fer by the air will depend on the relative temperature of the
soil surface and the air just above the soil. For a given
temperature gradient, this transfer rate will also be affected

by the wind velocity and turbulence. Guild (35) presented

the magnitude of this convective term as 20 to 40% of the net
radiation term on clear nights at Gila Bend in the Arizona
desert in April, 19u7. Cultural practices used to influence
soil temperature are shading, mulching and moisture control.

Soil temperature is also influenced by bed direction.
Shodbolt, C. A. (71) studied outdoor vegetable culture with
furrow irrigation in SW United States. On all beds except
those investigated in a NW-SE direction, with soil 1" deep,
one side was 5°-7° F warmer than the other. In all cases
the S or E exposures were warmer. Warmest bed by degrees
above 70° F was N-S. Coolest was NE-SW direction. These
findings are attributed to the combined effect of wind and
sun angle.

It appears that the wind has a greater influence on
soil temperature than the angle of the sun.

From the above, many factors are found to be influencing
soil temperature, the most important one is solar radiation.
What man can do concerning soil temperature is limited to
cultural methods, such as mulching, shading and adjusting

the direction of beds, etc.

Soil temperature and plant growth. Many researches
have been done on the effect of soil temperature or plant
growth. Many plants have been used, including grasses,
vegetables, ornamentals and trees.

Wort, D. S. (85) found that at day temperature 100° F
and night temperature 90° F. Greatest total dry weight of
Marquis wheat at harvest time were from plants grown at a
soil temperature of 71.6° F.

Ranay, etc. (61) and Kouds, etc. (#7) stated caloro
rice was found to yield the most rice at a constant root
temperature of 27° c. Japanese varieties of rice have been
shown to require root temperatures as high as 32° c for
Optimum germination and growth.

Hoagland, (#1) stated for barley, root growth at
20° c was about double that at either 10° or 30° c.

Bailey, J. S. and L. H. Jones, (u) growing blue-
berries with soil temperatures of 35° through 90° with 5°
increases found that plants with soil temperatures below
70° F were slower in starting growth than those above 70° F.
Total linear growth increased as soil temperature increased.
Plants grown at a soil temperature of 70° F or above tended
to be tall and upright, while those grown at 65° F soil
temperature or lower tended to be short and spreading.

Nelson, S. H. and Tukey, H. B. (56) studied the
effects of controlled root temperature on the growth of East
Malling Rootstock, used uu0, 55°, 66°, 77° F root temperature,

but at the same air temperature. The onset of new growth in

10

shoot and root was accelerated by a rise in temperature from
“0° to 77° P. All rootstocks showed very slight root growth
at uu° F, greatest root growth of MI, M II, M IX was at 55° F,
M II, M IX were killed at temperature above 55° F. Others
continued root growth with increasing temperature to 77° F.
At uu° F, the roots were thick, pearly white and non-branched,
while at 77° F they were slender, much branched, more or less
discoloured. Raising the root temperature increases root
cell maturation. As illustrated by differentiation of primary
tissue, vascular cambial activity and subsequent deposition
of secondary tissue. Shoot growth were proportional to
root growth.
Halms, F. F. (38) grew Eureke lemon, Marsh grapefruit,
and valencia orange with soil temperature ranges of 61° -
81°, 5u° - 72° F and 37° - 68° F at the Citrus Experiment
station in southern California. Plants, from rooted cuttings,
‘were grown one year outdoors. Based on total linear growth,
dry weight and fresh weight, he found lemon was the most
adaptable, grapefruit second, and the orange least adaptable.
Frances (32) Studied the effect of soil temperature
ton the growth of coffee-tree t0ps and roots. Air and soil
'temperatures of 26° c during the day and 20° c during the
lxight were found optimum for both top and root deve10pment.
1* 5° c increase or decrease of soil temperature caused a
marked retardation of top growth, and at constant soil
temperatures of 38° c or 13° c, top growth practically ceased,

although the air was maintained at optimum temperature.

ll

Benedict (7) found that the maximum weight of guayule-
shrub t0ps and the maximum rubber yield occurred at a soil
temperature of 27° - 29° c. The maximum weight of roots were
obtained at 18° c soil temperature while temperatures of
8° to 7° c inhibited growth. An air temperature of 28° c
was maintained during the experiment.

According to Nightingale (57), root and t0p growth
of peach and apple trees, was best at 18° c soil temperature.
At 7° c soil temperature, root primordia were present but
did not emerge, and at 35° c soil temperature the old roots
died and no new roots formed. The uncontrolled air tempera-
ture varied between 21° c and 15.5° c during the study.

Stone and Schubert (76) worked with ponderosa pine
seedlings transplanted into the greenhouse. They obtained
maximum increase in root length with a 25° c soil temperature
during the winter months. Little or no root elongation
occurred during summer, when inside greenhouse temperatures
reached a peak of 35° c or higher. Practically no root growth
took place at 10° c soil temperature at any time of year.

Darrow, R. A. (23) grew bluegrass (Egg pratensis) at
15°, 2u°, and 35° 0 root temperature. At 35°, he found erect
short top growth, small brown roots,densely tufted. At 15°,
tap growth was tall, and succulent, with many leaves, while
roots were large, white, succulent, and coarsely branched.

Stuckey, I. H. (77) used tanks with uniform temperature
of 50°, 60° and 80° F, air temperature 60° F to grow colonial
bentgrass. Those grown with a soil temperature of 60° gave

besthrowth and most extensive root system, those at 50° F

12

almost as good, but those at 80° F had very poor growth,
the roots matured early and finally died.

According to Arndt (3), in cotton plants, the mini-
mum temperatures for growth of primary roots was clearly
below 18° c; the maximum for any growth was above 39° and
visible injury soon appeared at the latter temperature. A
temperature range from 33° to 36° c was optimum for elonga-
tion of the primary roots during the first few days of growth
and produced the earliest emergence of secondary roots.

After 7 days of culture, the roots had the greatest total
length at 30° c and were most numerous at 27° c.

Johnson and Hartman (HZ) studied root growth of
tobacco in relation to soil temperature, found the best root
development in White Burley tobacco at 23° to 2u° c, with a
marked decrease at higher temperatures, and in the Connecticut
Havana variety, the best root development was at 26° to 29°
with a decided falling off at 31° to 32° c.

With soybean, soil temperature below 18° c retard
root growth whereas those between 18° c and 26° c showed
little difference. (Jones, F. R. 8 Tisdale) (us). These
results were re-examined by Barley and Cartter (28), who
found root temperatures from about 22° to 27° c appeared to
be most favorable for maximum dry-weight production of roots
and t0ps under a great variety of aerial environmental condi-
tions in the greenhouse.

F. R. Jones and Tisdale (H3) stated that Canadian

field peas did not flourish at a soil temperature of 30° c

13

and were intolerant to higher temperatures.

Burkholder (15) found no noticeable influence in
root growth of beans in soils at 18° and 26° c, suggested
the optimum soil temperature for beans lies between 22°
and 26° c.

Emsweller, S. L. and Tavernetti, J. R. (30) grew
gladiolus in cable heated soil, the average soil temperature
77° F (av. max. 80° F, av. min. 73° f), compared to unheated
soil average soil temperature 60° F (av. max. 63° F, av.
min. 58° F), the plants in heated soil flowered two weeks
ahead of the unheated soil plants, quality was the same,
and the former gave larger corms and more cormels.

According to Jones, Linus H. (nu), Gardenia veitchii

 

developed chlorosis at a soil temperature of 18° c or less,
and more intense chlorosis as soil temperature was lowered.

At soil temperature of 20° c and 22° c there were traces of
chlorosis, but it did not increase in intensity with time.
Davidson (2%) found when gardenia plants grown at high root
temperatures (82° F, 7u° F) produce more buds and larger
flowers but also highest amount of bud drop with result that
highest total production was less than those grown in relatively
cool soil (58° F, 66° F). The length of internodes, total
linear growth and flower size was reduced by low root tempera-
ture (58° F) with 70° - 7u° F air temperature, or by low air
temperature (65° - 68°) in Spite of warm 7u° root temperature.
The percentage of dry matter in young stems increased with

lower temperature. Gardenia veitchii is more temperature

 

1n

sensitive than Gardenia grandiflora.

 

Kopanek, Suton M. (#6) grew Poinsettia (Euphorbia

 

pulchirrima) plants in a greenhouse in which the air tempera-

 

tures were automatically maintained at 60° F during the night,
and 70° F on cloudy days and 75° F on sunny days. In a six-
day trial, the plants were grown with their roots exposed
to “0°, 50°, 60° and 80° F temperatures continuously. Plants
in the “0° plot wilted severely, and lost leaves. Plants at
other soil temperatures did not show wilting.

Allen (1) studied the effect of soil temperature on
flowers, used 52°, 60° and 72° F soil temperature with an
air temperature of 50° F. Column stocks flowered earliest
at soil temperature of 52° F, stem length unaffected.
Calendulas produced nearly twice as many flowers from plots
with 60° and 72° compared to 52° F also slightly longer stems
and stems having slightly less diameter. Snapdragon, Cheviot
Maid Supreme, at 60° and 72° soil temperature had more florets
per Spike but took 10 days longer to bloom and had shorter
flower clusters, although stem length remained the same com-
pared with those grown at 52° F soil temperature. Freesia at
soil temperature of 60° gave more blooms than at 52° F and
over twice as many blooms as those at a soil temperature of
72° F, but stem length was same in all treatments. Soil
temperature of 70° F resulted in earlier flowering by 2 weeks
in Freesias.

In a temperature study with roses, Kohl et a1 (#8),

used Peter's Briarcliff, Better Times and Pink Delight, and

15

soil temperatures of 80° F, 70° F and unheated check plots
which averaged 60° - 65° F. Night temperatures were 58° F,
day temperature 68° F, dull day 73° - 78° F bright day.
The highest soil temperature resulted in lowest flower produc-
tion. Shanks and Laurie (70) grew Better Times roses at root
temperatures varied by 0° F interval between 56° F to 72° F,
maintained 60° F at night, 65° - 70° F during the day, found
optimum temperature for growth of top was 5u° F. Progressive
decrease in the amount of roots was found as temperatures
increased from 56° to 72° F. Soil temperature influenced
the root diameter and number of root hairs, with the largest
diameter at 62° F, and root hairs few or absent at 72° F,
while the highest root numbers were found at lower tempera-
tures. Laurie and Stillings (52) studied rooting of rose
cutting. Their data showed that a rooting medium temperature
of about 21° c is generally better than 16° to 19° or 27° c.

Roberts, A. N. and A. L. Kenworthy (6M) grew straw-
berries in “5°, 55°, 65° and 75° F root temperature, main-
tained night temperature 50° - 60° F the first month, 60° -
65° F, the second month. Day temperature 70° F the first
month, 80° F the second month, found that on dry weight
accumulation basis, maximum growth of all parts during the
vegetative phase of development occurred at the root tempera-
ture of 65° and 75° F, with no significant difference in dry
weight of roots among all root temperatures.

Guyot, L. (37) grew 18 kinds of plants in clay pots
and plastic pots. The plants used were wheat, maize, flax,

potato, beet, radish, A ave, Pelargonium, tulips, Be onia,

 

16

Coleus, Calendula, sweet pea, Zinnia, Petunia, Nasturtium,

 

Marigold. In plastic pots, growth was found to be faster
and most vigorous, while flowering was often better (especially
with tulip) and yields high (eSpecially with potatoes). One
of the reasons given for this improved growth was that the
soil temperature is 1° - u° c higher in plastic pots than in
clay pots.

To summarize, under a certain air temperature condi-
tion, the growth of plants were found to be influenced by
soil or root temperatures. These soil temperature influences

varied with kinds, varieties of plants.

17

Soil temperature and water. Soil temperature has
been found to influence absorption and respiration in plants.

Kramer (H9, 50) stated: "the principal cause of
decreased water absorption by plants at low temperatures
appears to be the combined effects of decreasing permeability
of the root membranes and increased viscosity of water, re-
sulting in increased resistance to water movement across the
living cells of the roots." "Reduction in water absorption
caused by cold soil is of considerable ecological and practical
importance because it often produces winter injury and even
affects the growth of plants in greenhouses." If a tempera-
ture of 25° c and the water absorption rate of 100 is used
as the base, watermelon and cotton absorbed only 20% as much
water at 10° c; Georgia Collards absorbed 75%; Loblolly
and slash pine, 40%; and yellow and white pine, 60%. Ab-
sorption was reduced in all species, but more in species
which normally grow in warm soil than in species which
normally grow at least part of the year in cold soil. "The
difference between species presumably result chiefly from
differences with respect to the changes in viscosity and
permuability of the protoplasm of the roots caused by low
temperature."

Bohning, K. H. et a1 (10) grew tomato, sunflower,
red kidney bean in eight root temperature regimes: (a)
gradual change from 25° c to 5° c (b) abrupt changes from
25° to 20° (c) gradual change 20° to 5° c, (d) abrupt change

25° to 15° (e) gradual change 15° to 5°, (f) abrupt change

18

25° to 10°, (g) gradual 10° to 5°, and (h) abrupt 25° to 5°.
They found gradual reduction in temperature resulted in gradual
reduction in absorption rate, while abrupt reduction resulted
in abrupt changes to a value slightly below that of gradual
change. In red kidney bean sharp reduction in absorption
within 10° to 17° c range, indicating a change in viscosity
of protoplasm is probably the controlling factor. Absorption
rate in tomato and sunflower showed greatest reduction below
10° c with reported changes in water viscosity, indicates
that certain protoplasmic changes may have occurred which
reduced the viscosity changes in protoplasm as a limiting
factor in water absorption. With respect to sudden drops

to 25° to 5°, tomato and beans wilted severely but recovered.
Beans wilted and severely desiccated at 25 to 10 drop, and
uninjured portions recover very slowly.

Schroeder, R. A. (67) found that low soil or culture
solution temperature caused water deficiencies in cucumbers
and concluded that 70° F or slightly higher was the most
practical soil temperature for the crop.

Arndt, C. H. (3) using 9 week cotton plants found
intense sunlight and low soil temperature act in conjunction
to produce wilting. Wilting occurred in unshaded plants when
air temperature was 36° c and relative humidity 35% and soil
temperature 18° c. If shaded, no wilting happened under such
conditions. If the soil temperature was raised to 60° c under
similar conditions wilting occurred and whitish areas appeared

in the leaves. Cold root wilting was attributed to inadequacy

19

of the root system to take up sufficient water to compensate
for that lost through transpiration. High temperature
resulted in death of root tissues, which probably lost
ability to absorb water.

Vinokar, R. L. (78) studied lemons and soil tempera-
tures of 33° and 12-l“° c. He used plants at a state of
shoot rest, (no actively growing young shoots) and found
transpiration increases with increases in soil temperature.
He concluded that increased soil temperature is not the cause
of growth acceleration.

Bialoglowski, J. (9) studied the transpiration of
rooted lemon cuttings, using an air temperature of 25° c.
Transpiration during the period of darkness was unaffected
by root temperature changes of 0° to “0° c. When air tempera-
ture is 25° c in light, the plants transpire most rapidly
when the root temperature is over 35° c or below 25° c.

Cameron, 8. H. (18) used Valencia orange trees and
soil temperatures of “3° F, and 50 through 90 in 10 incriments.
Plants showed evidence of moisture stress when soil tempera-
ture was “8° P or lower. Lowering the soil temperature
from 90° to “5° F resulted in marked decrease in water loss.
Under usual environmental conditions transpiration during day
may be 10 times as great as at night.

Gray, G. F. (3“) found that at soil temperature of
100° F, strawberry roots are severely injured and leaf scorch
is due to inability to absorb water as rapidly as it is transpired,

at soil temperature of 85° F, root development was normal.

20

Indications are that strawberry varieties susceptible to
drouth and high temperature injury have a higher transpira-
tion rate than resistant varieties. He concluded that the
evaporative power of the air has a more direct effect upon
transpiration rate than has the root temperature.

Clements, F. E. and Martin E. V. (21) studied tran-

spiration of sunflowers (Helianthus annuus), using soil

 

temperatures ranging from 3“° F to 100° F. They found
transpiration varies little with soil temperature between

55° and 100° F, drops rapidly below 55° F, is reduced by half
at 38° F and approaches zero at 32° F. Stomata do not begin
closing until the soil temperature is about “0° F, but are
usually completely closed at 37° F. Plants recover rapidly
from wilting when soil temperature is raised. The experi-
ments were performed outdoors in summer in Santa Barbara,
California.

Drobnik (27) studied respiration curves of samples
of meadow soil and of compost at temperatures between 8° and
“8° c. Within the range of 8° to 28° c, increased tempera-
ture is reflected only in an acceleration of the processes
characterized by a Q10 = 1.6 - 2.0. Beginning at 38° c some
anomalies occur, partial inhibition of respiration can be
observed and maxima appear which resemble maxima found on
adding substrata. These maxima are attributed to reactive
oxidation of a part of the organic material of the soil
released by higher temperature.

From the above statements, we knew that both low and

21

high soil temperatures are unfavorable for plant growth as
concerning with water absorption and transpiration. In the
case of low soil temperature, water absorption is lowered

due to the high viscosity of water, decreased permeability of
cell wall, lowered protoplasm streaming; transpiration is
lowered due to the closing of stomata. In the case of high
soil temperatures, water absorption is lowered due to root
damages, but transpiration has not been lowered, so wilting

often occurs.

22

Soil temperature and nutrients. Many researches on
soil temperature and nutrients have been done, but only those
most pertinent to this study are reviewed here.

1” to the leaves

Sekioka, Hakobu (69) applied Sucrose C
of sweet potato plants with varying air and soil temperature.
Regardless of temperature, the sucrose was translocated from
leaf to roots and growing stem during 12 hours of darkness.
Accumulation in the root increased with decreasing tempera-
ture, with a corresponding loss from leaves. When the root
systems divided into halves and exposed to different tempera-

1“ moved

ture in darkness for 12 or 15 hours, the sucrose C
more rapidly from the leaves to 30° c than to “0° c roots
more rapidly; to 30° c than 20° c roots, and more rapidly to
20° c than to 10° c roots.
Vinokur, R. L. (78) used soil temperature of 33° c
and 12° - l“° c with lemon plants at state of shoot rest.
He found the increased plant growth upon an increase in root
temperature is not related to the simultaneous increase in
intensity of nitrate nitrogen absorption. Increase in root
temperature does not affect amino acid composition qualitatively,
but it does affect it quantitatively, indicating that different
mutabolic activities are affected differently by temperature.
Gukova, M. M. (36) used pea, lupine and bean as ex-
perimental materials. The root zone of the control plants
was kept at a temperature of 20° c, while that of experiment
plants were kept at 32° c. He found the plants grew equally

well and assimilated nitrogen in the root zone at both

23

temperatures. The weight of green matter of the plant and
the total intake of nitrogen were somewhat greater at a
substrate temperature of 32° than 20°. However, the phos-
phorus content in the experimental plants was always much
lower at the high temperature, this reduction reached 20 -
25% of the quantity of phosphorus in the control plant.
Still greater differences were observed in the absorption of
phosphorus in later growth period of the plant. The process
of exosmosis of phosphorus increases when a high temperature
exists in the root zone and causes a decrease on phosphorus
in the whole plant.

Proebsting, E. L. (60) grew two varieties of straw-
berries in the greenhouse, tops exposed to greenhouse tempera-
tures during March through June 1. Medium temperatures were
“5°, 55°, 65°, 75°, 85°, and 90° F. He found growth sharply
reduced at extreme temperatures, greatest increase in dry
weight at 75° F, and fruiting only at lower temperatures.
Greatest runner production was at 75° F. There was limited
variation in nitrogen content due to treatments, but potassium
in the roots was found to dr0p sharply with increasing tempera-
ture (about 55° F) while phosphorus content of plants was
highest at 65° F.

Bange, G. G. J. et a1 (5) studied the time course
of NH“ absorption by cut discs of potato tuber tissue at 0° c
and 20° c. The results point to the existence of a difference
of NHu concentration inside the absorbing tissue during steady

absorption at 20° c.

21+

Batjer, L. C. et a1 (7) used York Imperial apple
trees and root temperatures of “2° and “5° F, found low root
temperature caused a decrease in transpiration and earlier
closing of stomata, it thus appears that reduced water was
at least partially responsible for reduced growth of treated
plants. Low root temperature (“0° F) resulted in little if
any root growth. A root temperature of “0° F also appeared
to interfere with translocation of nitrogen reserves.

Shtrausberg, D. V. (72) used tOmatoes, maize, cabbage,
oats, and found that phosphorus uptake in plants fertilized
through the roots decreased to much greater extent if the
temperature around the roots is decreased than if air tempera-
ture is lowered. (used temperatures of 21° c and 7° c).
At low soil temperatures, nutrition by foliar application
is more practical, because uptake occurs more readily by this
method of application than by root feeding. He concluded
"when the temperature dropped to 11° - 12° c, the assimilaa
tion of phOSphorus was impeded, whereas that of nitrogen was
not. A drop in temperature from 11° to 7° c noticeably re-
duced nitrogen uptake in the plants, but only slightly affected
the uptake of phosphorus. A further drop in temperature to
5° - 1° c most noticeably impeded the assimilation of nitrogen
and to a somewhat lesser extent the uptake of phosphorus and
least that of calcium and sulphur, at low soil temperatures
potassium was the most readily assimilated of these elements."
"A drOp in temperature to 11° c somewhat hampered nitrogen

uptake in tomato plants, but did not impede protein synthesis,

25

at the same time, the ratio of nitrogen protein to non-
protein nitrogen increased slightly."

Wallace, A. (81) used both ammonium and nitrate forms
of nitrogen on citrus cuttings, found sufficient nitrogen is
absorbed by citrus roots at a temperature of “8° F to increase
nitrogen in the plant. This temperature is considerably
below that for root elongation in citrus. Greatest absorption
coeficient were found with a root temperature of between
58° - 7“° F, above 7“° P it leveled off and dropped off above
90° F. Uniform air temperature were used for all treatments.

Smith, R. L. and A. Wallace (73) using citrus and other
plant Species to study the absorption of calcium and potassium,
found the uptake of cation changes only slightly with tempera-
ture while uptake of anions generally increases considerably
with increasing temperature.

Wilcox et a1 (8“) used tomato plants to study the
effect of root zone temperature and phosPhorus concentration
in the soil on tomato growth and phosphorus uptake, constant
root temperatures of 56°, 58° and 60° F were used. 60° F
and 58° F caused increased dry weight production as compared
to 56° F. Both temperature and phosphorus treatment signifi-
cantly influenced the uptake of phOSphorus at the zero phos-
phorus level the uptake of phOSphorus at the 3 temperatures
was similar. At 50 and 100 ppm phosphorus the uptake at 58°
and 60° F was several fold greater than that at 56° F. Data
showed no phOSphorus temperature interaction and the increased

application of phosphorus in the root zone of tomato did not

26

overcome the effect of low temperature.

Lingle, J. C. (5“) reported that growth of tomatoes
sharply reduced at soil temperature of 50° - 55° F contrasted
to 60° - 65° or 70° - 75° F. Greatest concentration of phos-
phorus in the plant occurred at soil temperature in the 60° -
65° F range, (85% over non-fertilized plant) contrasted to
59% in 50° - 55° region and “5% in the 70° - 75° range with
only 23% in the 80° - 88° F range. The increased absorption
of phosphorus and increased growth at higher soil tempera-
ture attributed to: (1) greater reSpiratory activity at
higher temperatures. (2) favorable effect of higher soil
temperature on rate of root growth, hence increased absorption
surface. (3) increased water absorption at higher soil
temperatures.

Lacascio, S. J. et a1 (51) reported that root tempera-
ture near 50° F reduce tomato growth Sharply, also reported
tomato response to phosphorus was greater at low soil tempera-
ture than at high soil temperature, and that the difference
in reSponse at low temperature was not a direct effect of phos-
phorus availability at low temperature. The soil temperatures
used were 55°, 70°, 85° F.

Apple, 8. B. Jr. et a1 (2) used pole beans in a green-
house study of the effect of soil temperature, and found
applied phosphorus more effective at 63° F than at 82° F.
63° F and 82° F were the soil temperatures used, air tempera-
ture were 55° - 60° F at night, 65° - 75° F during the day.

Robinson, R. R. (66) suggested the more rapid uptake

27

of phosPhorus in clover at higher temperatures is associated
with the coefficient of absorption rather than increased
phosphorus in the soil solution. As temperature increases,
plants are able to absorb more phosphorus from the soil solu-
tion. Since banding of phosphorus fertilizer increases the
concentration of the soil solution, temperature then becomes
less important to phosphorus uptake.
Robinson, R. R. (65) grew Ladino clover in Dekalb
soil, maintained optimum moisture content for 2 months, used
soil temperature 15°, 20°, 25°,35°, “0°, “5° c, and 3° c,
with phosphorus incubation or with no incubation treatment.
He found 15° - “5° c resulted in very poor plant growth,
compared to 3° c with incubation or with no incubation treat-
ment. He concluded poor growth resulting from incubation at
high temperature was due to a decrease in available phOSphorus.
From the review above it is clear that soil tempera-
ture has some effects on the absorption and translocation of
nutrients in plants. Generally speaking, a higher soil tempera-

ture is more favorable for absorption of nutrients by plants.

OPTIMUM SOIL AND AIR TEMPERATURE FOR ECONOMIC PLANTS

PLANT

Apple
Barley
Beans

Bermuda
grass

Blueberry

Blueberry
cutting

Bluegrass
Calendula

Canada
bluegrass

Colonial
bentgrass

Coffee
tree

Coniferous

hardwood
cutting

Corn
East
Malling

rootstock

Eureka
lemon

ORIGIN

Temperate
Temperate
Temperate

Sub-
trOpical

Temperate

Temperate

Temperate
Temperate

Temperate

Temperate

Tropical

Temperate

Temperate

Temperate

Sub-
tropical

28

KIND

Tree
Biennial
Annual

Perennial

Shrub
Shrub

Perennial
Annual

Perennial

Perennial

Shrub

Tree

Annual

Tree

Tree

OPTIMUM
SOIL
TEMPER-
ATURE
6“.“°F
68.0°F
71-78.8°F

100.2“°F

70°-90°F

69.8°-71°F

59°F
60°-72°F
50°F

60°F

78.8°F
day
68°F
night

50°-55.“°F

7"}. 6°-
81.6°F

55°F

61°-81°F

OPTIMUM
AIR
TEMPER-
ATURE

100.2“°F

50°F

50°F

78.8°F
day
68°F
night

REFERENCE

“1
15

7“

68

13

13

77

32

53

26

55

78

PLANT

Field pea
Canadian

Freesia

Gardenia
Veitchii

Gladiolus

Guayule
plant

Grapefruit
Grapefruit
(Marsh)
Hemp

Holly
cutting

Mesquite
(prospis
verotina)

Ocotillo

ORIGIN

Temperate

warm

Warm

Warm
Tropical
Sub-
tr0pical

Sub-
tropical

Warm

Temperate

Temperate
dry

Temperate

(Fouguieria dry

Splendens)

Kentucky
bluegrass

Temperate

Onion, Red Warm

Globe

Onion,
Yellow
Bermudki

Warm

29

KIND

Annual

Corm

Shrub

Corm

Tree

Tree

Tree

Annual
Shrub

Succu-
lents

Succu-
lents

Perennial

bulb

bulb

OPTIMUM
SOIL
TEMPER-
ATURE

OPTIMUM
AIR
TEMPER-
ATURE

below
80°F

60°F

(most
flowers)

70°F
(early
growth)

66°F

77°F

'79.8°-

83.6°F
78.8°F

61°-81°F

80°F 59°F

5“.“0-
7“.6°F

95°F

95°F

50°F 50°F

below 68°F
(root)

68°F and
above (top)

68°F (root)
77°F (top)

REFERENCE

“3

2“

3O

38

38

56

53

20

20

1“

79

79

PLANT

Onion,
White
Portugal
Onion,
Crystal
wax
Bermuda

Orchard
grass

Pea
Peach
Pine,
loblolly

Pine,
white

Pine,
ponderosa

Pineapple

Poa

praetensis

Poinsettia

Potato

Prickly
pear
(opuntia

versicolor)

Redwood
seedling

Rose

ORIGIN

Warm

Warm

Temperate

Temperate

Temperate
Temperate
Temperate
Temperate
Sub-
tropical

Temperate

Tropical

Warm

Temperate
dry

Temperate

Temperate

30

KIND

Bulb

Bulb

Perennial

Annual
Tree

Tree

Tree

Tree

Perennial

Perennial

Shrub

Tuber

Succulent

Tree

Shrub

OPTIMUM
SOIL
TEMPER-
ATURE

OPTIMUM
AIR
TEMPER-
ATURE
68°F (root)

71.6°F

(bulbing)
68°F(root)

71.6°F
(bulbing)

69.8°F 69.8°F

71.6°F

6“.“°F 69.8°-

60.8°F
68°-77°F
81.8°F
77°F
83.6°F
59°F

50°-80°F 60°F

65°F
68°F

68°F

95°F

6“.“°F 7“.6°F

60°-65°F

REFERENCE

80

80

13

11
57

76

82

23

“6

16

20

no

58°F (night) 31

PLANT

Rose
cutting

Rice,
caloro

Rice,
Japanese

Strawberry

Snapdragon

Sugarbeet

Soybean

Stock,
column

Tobacco,
white
burley

Tobacco

Connecticut

Havana

Tomato

Tomato

Wheat,
Spring

Wheat,
winter

ORIGIN

Temperate

Temperate

Temperate

Temperate

Temperate

Temperate

Temperate

Temperate

Warm

Warm

Warm

Warm

Temperate

Temperate

KIND

Shrub

Annual

Annual

Perennial

Annual

Biennial

Annual

Annual

Annual

Annual

Annual

Annual

Annual

Biennial

OPTIMUM
SOIL
TEMPER-
ATURE

OPTIMUM
AIR
TEMPER-
ATURE

69.8°F

79.8°F

83.6°F

50°-60°F
60°-65°F

65°-75°F

60°-72°F 50°F

above
69.8°F

710-790 8°P

60°-72°F 50°F

72. 8°-
7“.6°F

78.80‘
83.“°F

52°-58°F
(night)

56°-57°F

7.4060"
81.8°F
(shoot)
85.0°F
(Stem and
Fruit)

60.8°-
68.8°F

53060-
60.8°F

REFERENCE

52

29

29

60

58

28

“2

“2

17

63

85

85

MATERIALS AND METHODS

Three kinds of flowering plants were used in this

experiment, namely, carnation (Dianthus caryophyllus), Easter

 

lily (Lilium longiflorum) and Geranium (Pelargonium hortorum).

 

 

Well rooted cuttings of uniform size of carnation,
cv. Improved White Sim were selected and potted into 5 inch
pots on April 9, 1963 in steam sterilized greenhouse potting
soil. There were 8 replications within each soil temperature
treatments.

Easter lily cv. King were used. Seven cm. diameter
bulbs were chosen and potted into 6 inch pots on March 28,
1963, with steam sterilized potting soil, with 5 replications
within each treatment. The bulbs had been in “0° F cold
storage November 1, 1962 to the potting date.

Geranium cv. Pink Cloud, uniform well-rooted cuttings
having three leaves, were potted into 5 inch pots in steamed
potting soil on April 2, 1963. There were 8 replications
within each treatment.

Three soil temperatures were used in this experiment;
80° F, 60° F and “0° F. These soil temperatures were constantly
maintained by placing pots in cans in separate water tanks at
the appropriate temperature.

These water tanks loaned by Soil Science Department,
and have been used successfully since 1957. They were milk

32

33

cooling tanks of dimensions of 3“ inches in width, 52.5

inches in length, and 28 inches in depth, with 3.5 inch wall
and bottom which were insulated inside. Equipments were added
such as:

(1) Suspension float board for placing plant pots in cans,

 

and can be adjusted to any desired depth.

(2) Over flow drainage, by which a constant water level can

 

be maintained.

(3) Circulation pump, made the water circulated in the tank

 

constantly to maintain an even water temperature over the
entire tank.

Additional equipment was regulating the water tempera-
ture. In the 80° degree tank, an electrical thermostat and
a heater bathed in the water tank were used. The heater
warmed the water, and thermostat controlled the temperature.
In both 60° degree and “0° degree tanks, thermostat and
refrigeration compressor were used to maintain the desired
temperature.

In operation the first step was putting the cans on
the board and adjusting the depth of board so each was two-
thirds submerged. In order to maintain the same water level
throughout the entire experimental period, water was added
now and then to compensate for the loss from evaporation.
The thermostats were adjusted to maintain the appr0priate
temperatures. Usually the temperatures became stabilized
within “8 hours.

The air temperature was maintained at about 68°F at

3“

night through the entire experimental period except for a few
nights. During the day time, air temperature was between

70° F and 100° F, and above 100° F sometimes on hot days.

The soil temperature remained constant and did not Show any
change through the entire experimental period. Previous work
with this equipment had revealed variations of 2° F. Plants
were watered as required, and fertilized with half strength
Plant Marvel (12 - 31 - 1“, one-half teaspoon per two gallons
of water) once every fourteen days. Weekly records were taken
on the growth of plants, height of carnation and lily, number
of leaves of geranium.

In case of carnation, the experiment terminated as
the flower fully bloomed, measurements were taken on (1) days
to bloom, (2) length of stem (in cm.), (3) flower size, (“)
number and length of side shoots, (5) dry weight of the t0p
(in gm.), and, (6) dry weight of the roots (in gm.).

In case of Easter lily, the experiment terminated
when the first flower fully opened, growth was measured as
(1) days to emergence, (2) days to bloom, (3) length of stem
(in cm), (“) number of leaves, (5) number of flowers, (6)
flower length (in cm).

For geranium, growth was measured as (1) days to first
bloom, (2) number of leaves, (3) leaf areas, (“) number of
flowers, (5) number of florets, (6) length of flower stem,

(7) dry weight of the top and roots. The experiment was
terminated on July 7, 1963.
As the plants were healthy through the entire period,

no pest control had been used.

RESULTS

GENERAL OBSERVATION

Generally speaking, lily plants in this experiment
appeared normal except one lily plant in 80° F treatment
produced one flower of “ petals and “ anthers, this might
be the result of long storage period which causing decline
of vitality (75). Geranium plants in “0° F treatments
had plain leaves in contrast to those in 60° F and 80° F
treatment with crinkled leaves. The leaf color was the
same. No marked differences in appearance were observed in
carnation plants.

The underground portions of the plants appeared to
be more influenced by soil temperature than the tops of the
plants.

The roots of carnation Showed marked differences due
to treatment. Those in “0° F pots were short, slender,
numerous and filled the upper half of the pot, those in
60° F and 80° F pots were longer, tougher, fewer in number
and were distributed throughout the soil.

Because the lilies in “0° F treatment had not
flowered by the end of this experiment, only plants of 60°
and 80° soil temperatures were observed. The roots in 60° F
pot were numerous, longer, both in stem roots and basal roots;

those in 80° F pots were shorter and fewer.

35

36

The root system of Geranium Showed great difference
among soil temperature treatments. Those in “0° pots were
slender, short, white in color, numerous, not differentiated
into branch and side roots, and only filled the upper part
of the pot. Those in 60° F pots were several large half-
suberized branched roots, brown in color, each bore many
Side roots. Those in 80° pots had several suberized branched
roots brown in color, and bore a few or no side roots. Roots
at both 60° and 80° filled all the pots. This phenomena was
found to be identical with those of Lovell peach seedlings,
within a soil temperature range of 7.2 - 35° c, "the tendency
towards thicker fleshy roots at low temperature and towards
fibrous suberized roots at the higher temperature was
apparent." (Proebsting 19“3) (59).

Similar situation occurred in rose, (Shanks and
Laurie 70), the roots with the largest diameter at 62° F,
and root hairs few or absent at 72° F. In case of cotton,
(Arndt 3) the roots had the greatest total length at 30° c and
were most numerous at 27° c. Nelson, S. H. and Tukey, H. B.
(56) worked with East Malling rootstock, found the roots
were thick, pearly white and nonbranched at ““° F, while at
77° F, they were slender, much branched, more or less dis-
colored, concluded that raising the root temperature increases

root cell maturation.

37
CARNATION

Table I indicated that there were no significant
differences in growth characters which may be attributed
to the effect of soil temperature, such as days to bloom,
number of nodes, height of flower and root dry weight.

The significant differences found were (1) the number
of side shoots was lower in plants grown in “0° F soil treat-
ment than those in 60° F treatment; (2) the total growth
and average length of Side Shoots of plants in “0° F treat-
ment was inferior to those grown in 80° F and 60° F treat-
ment; (3) the flower diameter of “0° F treated plants was
also inferior to those in both 80° F and 60° F treatment;

(“) the stem length of plants in “0° F treatments was shorter
than those in 60° and 80° F treatments; (5) the total dry
weight of plants in “0° F treatments was smaller than that

in 60° F treatment; (6) the top dry weight of plants in

“0° F treatment was smaller than those in 60° F and 80° F

treatments.

TABLE I

GROWTH OF CARNATION AS RELATED TO SOIL TEMPERATURE

 

 

 

MEASUREMENT SOIL TEMPERATURE °F SIGNIFICANCE OF
(Mean of 8 , DIFFERENCE BETWEEN
Plants) 80 60 “0 Temp 80 80 60" D
60 “U '“0
Days to bloom 53.75 51.75 53.75 NS
Stem length 55.06 55.13 “5.31 1% NS . 5% 5% 1.535
(cm)
No. of nodes 11.00 11.12 10.38 NS
No. of side 3.50 5.00 1.88 1% NS NS 5% 2.05“
shoots
Mean length of 15.61 13.90 6.71 1% NS 5% 5% “.28“
side shoots
(cm)
Total growth 55.17 68.92 1“.06 1% NS 5% 5% 23.366
of side shoots
(cm)
Diameter of 6.68 6.“3 5.87 1% NS 5% 5% 0.“533
flower (cm)
Height of 5.12 “.68 “.75 NS
flower (cm)
Total dry 5.950 7.212 “.637 5% NS NS 5% 1.8921
weight (gm)
Top dry 5.33 6.32 3.81 1% NS 5% 5% 0.9539
weight (gm)
Root dry 0.638 0.912 0.700 NS

weight (gm)

 

NS - Non significant

D:

QS = (See Snedecor, F. W.:

Statistical Methods, 1957 P. 251)

39
EASTER LILY

Table II indicated obviously that “0° F soil tempera—
ture is not favorable to Easter lily growth as shown by the
significant difference in the days to emergence. As they did
not bloom when this experiment ended, it was impossible to
have more data. So only two soil temperatures were used for
comparing other items.

The data showed that there was no significant differ-
ence between 80° and 60° at the 1% level in the items such
as days to emergence, stem length, number of leaves, number
of flowers, top dry weight, root dry weight and flower length.
The only differences were (1) significance of difference in
days to bloom occurred at 1% level, and (2) significant
difference in total dry weight at 5% level. The former favored
plants in 80° F treatment, flowered 6.6 days earlier than

60° F plants, the latter favored plants in 60° F treatment.

“0

TABLE II

GROWTH OF EASTER LILY AS RELATED TO SOIL TEMPERATURE

 

 

 

MEASUREMENT SOIL TEMPERATURE °F SIGNIFICANCE OF
(Mean of 5 DIFFERENCE BETWEEN
plants) 80 60 “0 Temp 80 80 60 23
60 “0 ‘F0
Days to 21.4 21.8 65.2 1% N82 5% 5% 1.uu7
emergence
Days to bloom 76.0 82.6 - 1%
Stem length (cm) 28.9 31.0 - NS
Number of leaves 62.2 6“.2 - NS
Number of 1.2 1.“ - NS
flowers
flower (cm)
Total dry 5.“6 9.56 - 5%
weight (g)
TOp dry “.06 6.52 - NS
weight (g)
Root dry 1.0“ 3.0“ - NS
weight (g)

 

1) As plants in “0° F were remained vegetative when this
experiment terminated, no more data could be taken.

2) NS - non significant

3) D = OS X (see Snedecor, G. W.:

1957, p. 251)

Statistical Methods

“1

GERANIUM

Table III showed that there were no Significance of
difference in days to first bloom concerning these soil
temperatures. As for other items, there were significant
differences. Plants in “0° F treatment were inferior to
those in 80°, and 60° treatment in number of leaves, leaf
areas and total dry weight; were inferior to plants in 80°
treatment in t0p dry weight, were inferior to those in 60°
in number of flower clusters. As for the leaf area, plants
in 80° treatment had the largest, plants in 60° F the second,
and those in “0° F the third. As far as root dry weight was
concerned, plants in 60° F ranked the first, those in 80° F

the second, and those in “0° F the third.

GROWTH OF GERANIUM AS RELATED TO SOIL TEMPERATURE

“2

TABLE III

 

 

 

 

MEASUREMENT SOIL TEMPERATURE °F SIGNIFICANCE OF

(Mean of 8 DIFFERENCE BETWEEN

plants) 80 60 no Temp 80 30 60 D

60 EU F0

Days to first 53.50 “9.50 55.37 NS
bloom

No. of leaves 30.25 31.50 20.62 1% NS 5% 5% “.85

Leaf area (cm)2893.12 583.75 3“8.75 1% 5% 5% 5% 151.263

Flower stem 15.16 l“.50 11.62 1% NS 5% 5% 2.316
length (cm)

No. of flower 3.5 “.0 2.9 5% NS NS 5% 1.006
clusters

Florets per “3.26 “3.3“ 3“.75 5% NS 5% 5% 2.786
cluster

Top dry 22.35 19.68 l“.72 5% NS 5% NS 6.29
weight (gm)

Root dry 3.96 5.26 2.38 1% 5% 5% 5% 1.03“
weight (gm)

Total dry 26.“3 25.07 17.10 1% NS 5% 5% 6.“7
weight (gm)

NS 3 Non significant

D: QS x (see Snedecor, F. W.: Statistical Methods, 1957, p. 251)

DISCUSSION

By observing the above mentioned facts, it was clear
that soil temperature played an active role upon plant growth.

In case of carnation, a perennial from temperate
region, no significant difference occurred among the flower-
ing date of three soil temperature treatments. In other
words, plants in “0° F could bloom at about the same time as
those in 60° F and 80° F treatments, though the flower diameter
was smaller and stem length shorter. Significant differences
were found that the number, total growth and average length
of side shoots was smaller; total and top dry weight was
smaller, too. This meant plants in “0° F treatment were un-
able to produce more branches for further flowering beyond the
first bloom. As the plants were all well rooted at the beginning
and no significant differences were found among the root dry
weight afterwards, then it could be assumed that it was the
activity of roots which caused the difference. Forty degree
soil apparently lowered the activity of roots with regard to
absorption of water and nutrients, but sufficient growth was
attained to support the first flower. The cause of low activity
of roots under low soil temperatures has been explained as
due to high viscosity of water, decreased permeability of cell

wall, and lowered protoplasm streaming by Kramer (“9).

“3

an

In case of strawberry plants, Robert, S. N. and
Kenworthy, A. L. (6“) found also that no significant differ-
ence in dry weight of roots among all root temperatures (“5° F,
55° F, 65° F, 75° F).

No significant difference was found between 60° and
80° treatment. As it was easier to maintain a soil tempera-
ture of 60° than 80°, so 60° F could be considered as the
ideal soil temperature for carnation.

As there was great variation in the measurement of
characters, the original data are listed as Appendix I.

The same Situation existed in geranium, a perennial
from sub-tropics. No differences were found among different
soil temperature treatments with regard to days to first bloom.
Plants in “0° F bloomed in about the same number of days as
those in 60° and 80°, but the number of flower clusters,
number of florets per flower, and length of flower stem were
smaller as also was the vegetative growth such as number of
leaves, leaf area and dry weight. These may be explained as
the result of low activity of roots caused by low soil tempera-
ture.

The only significant difference between 60° and 80°
treatments was in leaf area and root dry weight. Plants in
60° F had the larger root dry weight and plants in 80° F had
the larger leaf area. AS the flowering characteristics were
almost the same between plants in 60° and 80°, and from aes-
thetic point of view it would be better to have less foliage
for the same amount of flowers, so it was more reasonable to

think 60° was more suitable to culture of geraniums. Another

“5

consideration is the cost of fuel, it is less for 60° soil
temperature than 80° F. As there was great variation in the
measurement of character, the original data are listed as
Appendix II.

As for Easter lily, a bulbous plant from a warm region,
among these soil temperatures, “0° F delayed their emergence
and growth. No significant differences were found between
60° F and 80° F in days to emergence. However, significant
differences existed between plants in 60° F and 80° F in days
to bloom, plants in 80° F soil bloomed 6.6 days prior to those
in 60° F. The total dry weight, however, was greater in the
plants grown in 60° F soil. AS the lily plants were not well
rooted when they were planted, it may be assumed that “0° F
was not favorable for emergence and root formation of lilies,
but 60° F and 80° F were both favorable. As the roots were
formed, the root activity appeared greater in 80° plants than
60° plants because the plants in 80° bloomed 6.6 days earlier.
This could be explained by Q10 = 1.2 - 1.3, the physiological
process increases 1.2 - 1.3 fold by each increase of 10° c
(18° F), and this could be brought into practical use by raising
soil temperature to hasten lily flowers.

As there was great variation in the measurement of

characters, the original data are listed as Appendix III.

SUMMARY

The effect of soil temperature upon the growth of carna-

tion (Dianthus caryOphyllus, L. ), Easter lily (Lilium longi-

 

 

florus, Thumb) and Geranium (Pelargonium hortorum, Bailey)
was studied. These plants were grown on pots in greenhouse
potting soil, put into separate water tanks maintaining soil
temperatures of 80°, 60° and “0° F. Air temperature main-
tained 68° F at night in the greenhouse.

Growth was measured as dry weight, days to bloom,
and number of leaves for all plants. Additional measurement
was made of number and total growth of side shoots, and size
of flower in carnation; days to emergence, size of flower,
number of flower in Easter lily; and leaf area, number of
flower cluster, number of floret per flower in Geranium.

Significant differences were found in carnation plants
concerning the number and total growth of side Shoots, and
total and tOp dry weight. Plants in “0° F pots were inferior
to those in 60° and 80° treatments. No significant difference
existed between 60° and 80° F treatments. As for other items,
no Significant differences existed among the treatments.

In Easter lilies, plants in “0° F treatment were de-
layed in emergence, and had not flowered when this experiment

terminated. No significant difference was found between 60°

“6

47

and 80° treatment in days to emergence, but plants in 80° F
treatment were flowered 6.6 days earlier than 60° F treatment.
No significant differences were found among other items.

In Geranium, plants in “0° F treatment were inferior
to those in other treatments in reSpect to leaf area, number
of flowers, florets pawflower and dry weight. No significant

difference existed between 60° and 80° treatments.

3.

10.

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APPENDIX I

CARNATION ROOT TEMPERATURE STUDY

55

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APPENDIX II

GERANIUM ROOT TEMPERATURE STUDY

57

58

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APPENDIX III

EASTER LILY ROOT TEMPERATURE STUDY

59

60

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HICHIGQN STQTE UNIV. LIBRQRIES

 

31293011097817