Crop Growth under Extreme Environments
High and Low Temperatures
Plant Responses to Extreme Environments
High Temperature Injury
K. Raja Reddy
Mississippi State University
Mississippi State, MS
It’s very
hot
It’s too
cold
Plant Responses to Extreme Temperatures
I need some
water
• Few plant species can survive a steady high
temperatures above 45 °C
9Actively growing tissues can rarely survive over
45°C
9However, non-growing cells or organs (Pollen and
seed) can survive much higher temperatures.
- some pollen up to 70 °C
-some seed up to 120 °C.
• Heat stress is also a major problem in greenhouses,
where low air speed and high humidity decreases leaf
cooling and thus affecting leaf/canopy temperatures.
Plant Responses to High Temperatures
• Plants do adapt to high temperature:
9 Reflective leaf hairs and waxes
9 Leaf rolling, and vertical leaf orientation
9 Small leaves and dissected (okra) leaf morphology
9 Synthesis of heat-shock proteins (HSPs)
Ö Help cells withstand heat stress
Ö However, the functions of all HSPs are not yet fully
known, but many act as molecular chaperons, help
stabilize and fold proteins, assist in polypeptide
transport across membranes, protect enzymes, etc.
Plant Critical Processes at High Temperatures
• Photosynthesis and respiration, and conductivity will be
affected by high temperatures.
• However, photosynthesis declines faster than
respiration and conductivity at high temperatures.
• The point when the amount of CO2 fixed equals to the
amount of CO2 released by respiration is called
temperature compensation point. At this point and
beyond, the carbon is not replaced, and carbohydrate
reserves will be used for cellular functions.
• Therefore, the imbalance between photosynthesis and
respiration causes deleterious effects at high
temperatures.
1
Climatic Zones and Temperature Conditions
Plant Critical Processes at High Temperatures
• The question is how do plant groups respond to high
temperatures?
• Enhanced temperatures are more detrimental in C3
plants than in C4 or CAM plants because of rates of
both dark and photorespiration are increased more in C3
plants.
• What happens to C3 plants under elevated CO2
conditions?
Long-term Average Temperatures
for Four US Cotton Producing Areas
40
40
35
30
Phoenix, AZ
Phoenix, Arizona
Corpus Christi, Texas
20
25
Temperature, ° C
30
Maros, Indonesia
20
15
10
0
Days above Optimum = 111
Days above Optimum = 85
-10
40
Bakersfield, California
Stoneville, Mississippi
30
20
10
Stoneville, MS
10
5
0
0
0
50
100
150
200
250
300
350
Days above Optimum = 0
Days above Optimum = 36
-10
0
50 100 150 200 250 300 350 0
Day of the Year
50 100 150 200 250 300 350
Day of the Year
Temperature Conditions - Diurnal Trends
Mississippi State, MS - 1995
Hourly Temperatures for July 1995
Mississippi State, MS
40
40
35
Temperature, °C
35
Temperature, °C
Temperature, °C
Long-Term Average Temperatures
30
25
20
30
19 Aug. 1995
25
20
15
2 May, 1995
10
23 Sep. 1995
5
0
15
0
5
10
15
Days
20
25
30
0
2
4
6
8
10 12 14 16 18 20 22 24
Hours (CST)
2
Diurnal temperature data recorded in June 1989 at Fatehpur,
Rajasthan, India, (Latitude 27°C 37'N).
5 cm depth of soil (▲)
0.5 cm depth of soil (●)
150 cm above the soil surface (■)
Climate Change and Crop Production
• Past changes in greenhouse gases has resulted about
0.6 °C increase in global average temperature
during the last century.
• If current and future rates of changes in greenhouse
gases and other land-use changes continue, then,
these changes will exacerbate the natural climate
changes and may result in:
- 2 to 6 °C warmer temperatures
- More frequent episodes of extreme events (heat,
cold, drought, excessive rainfall resulting in floods,
severe hurricanes, etc.).
Howarth, 1991
Cotton
Second green revolution
to overcome
environmental stresses
5 bolls per plant with 6 g per boll
will yield 1.98 bales per acre
High Temperature Effects on Cotton Fruit
Production and Retention
Optimum Temperature
No Injury to Reproductive Parts
Pima Cotton Responses to Temperatures
The next 3 video clips show cotton responses to optimum (30/22°C, day/night),
higher (35/27°C) and super-optimum (40/32°C) temperatures.
Notice that the plants grown in optimum temperatures are producing both
vegetative and reproductive structures continuously and there is no abscission
of squares or fruiting structures. Plants grown in 35/27°C are producing
luxuriant vegetative growth, but some of the squares are being abscised due to
excessive heat. If plants are grown in 40/32°C, the vegetative growth is
reduced to certain extent compared to plants grown in other temperatures, but
there is a complete reproductive failure (no flower-bud initiation and even
fruiting branch production) due to excessive heat.
3
Higher Temperature Injury
Partial Injury to Reproductive Parts
Super High Temperature Injury
Total Reproductive Failure, Including
Fruiting Branch Production
High Temperature Effects on Cotton – Upland Cotton
High Temperature Effects on Cotton – Pima Cotton
100
70
Produced
60
Retained
Bolls and Squares, no. plant-1
Bolls and Squares, no. plant-1
80
50
40
30
20
10
0
15
20
25
30
CO2 µl l-1
75
700
350
50
25
0
15
35
20
25
30
35
Temperature, °C
Temperature, °C
Environment - Crop Growth – High Temperature
Injury to Reproductive Parts
Environment - Crop Growth – High Temperatures
Injury to Reproductive Parts
Table 1. Effect of temperature on cotton growth, cv. Stoneville 825,
harvested 49 days after initiation of temperature treatments.
350
tretments are imposed at first flower. Standard error of the
mean values are shown.
300
20/12
25/15
Total Wt.
242
320
% of Optimum
73
97
30/20
35/25
40/30
Grams per Plant
330
100
293
225
88
68
Bolls Produced
250
Bolls, no. m-2
Day/Night Temperature, °C
200
150
100
CO2, µl l-1
Bolls
17
63
143
17
0.8
% of Optimum
12
44
100
12
0.6
Bolls Retained
350
50
0
25
700
26
27
28
29
30
31
32
33
34
35
Temperature, °C
4
High Temperature Injury
Temperature and CO2 Interactions
Projected Temperatures and Cotton Development
Vegetative Biomass
Days to the Event
Square
Flower
500
Open Boll
1995 minus 2°C
33
65
144
1995 plus 0°C
26
51
101
1995 plus 2°C
24
48
94
1995 plus 5°C
21
42
77
1995 plus 7°C
19
39
No Fruit
Vegetative Weight, g plant-1
Treatment
-1
360 CO2 µL L
-1
720 CO2 µL L
450
400
350
300
250
200
150
100
50
0
1995-2
No significant differences were observed between CO2 levels
1995
1995+2
1995+5
1995+7
Temperature Deviation from 1995, °C
High Temperature Injury
Temperature and CO2 Interactions – Cotton
Fruiting Sites
360 CO2 µl l
250
720 CO2 µl l
Retained Bolls
80
-1
Retained Bolls, no plant-1
-1
300
Bolls and Squares, no plant
High Temperature Injury
Temperature and CO2 Interactions – Cotton
-1
200
150
100
50
70
360 CO2 µl l
60
720 CO2 µl l
-1
50
40
30
20
10
0
0
1995-2
1995
1995+2
1995+5
1995-2
1995+7
High Temperature Injury
Temperature and CO2 Interactions – Cotton
Boll weight
1995+5
1995+7
Fruit Production Efficiency
400
-1
360 CO2 µL L
-1
720 CO2 µL L
Fruit Production Efficiency
(g kg-1 Dry Weight)
300
1995+2
High Temperature Injury
Temperature and CO2 Interactions – Cotton
400
350
1995
Temperature Deviation from 1995, °C
Temperature Deviation from 1995, °C
Boll Weight, g plant-1
-1
250
200
150
100
300
200
100
700 µL L-1
350 µL L-1
50
0
1995-2
1995
1995+2
1995+5
1995+7
Temperature Deviation from 1995, °C
0
24
26
28
30
32
34
Temperature, °C
5
High Temperature Injury
Using Simulation Models – Cotton Lint Yield
Cotton Lint Yield and Climate Scenarios
High Temperature Effects on Cotton
Heat-blasted Squares – San Joaquin Valley, California, USA
2200
Lint Yield (kg ha-1)
2000
1800
C urrent + A m bient C O 2
C urrent + E levated C O 2
F uture + E levated C O 2
1992
1993
1989
1600
1984
1400
1200
1980
1000
800
H ot D ry
H ot W et C old D ry C old W et N orm al
C lim ate C hange S cenario
Reddy et al. 2002
High Temperature Effects on Cotton
Heat-blasted Flowers – San Joaquin Valley, California, USA
High Temperature Effects on Cotton
The high temperature injury in cotton to reproductive
growth and development is not fully understood so for.
High temperature causes some heat-sensitive
cultivars/species (Pima cotton) to be vegetative (total
reproductive failure and the reproductive induction process
is sensitive). Not much is known why plants stay
vegetative at those high temperature conditions.
Once the flower-buds (squares) are formed, exposure to
extremely high temperatures (35/27oC) will result in
abscission of squares.
High Temperature Effects on Cotton
High Temperature Effects on Cotton
• Nutrient starvation is not the factor that causes that
square abortion because plants grown in elevated or
twice ambient CO2 and under optimum nutrient
conditions also drop those squares, and the nutrient
demand for squares is minimal.
• Breeders need simple and quantitative methods to
screen genotypic variability and to find or breed a
genotype to a niche environment for optimum crop
production.
• The evidence suggest that the 2 weeks prior to and 1
week post flower is the most sensitive stage in cotton.
• Biotechnology may play a role in developing cultivars
that are more heat-tolerant.
• Systematic evaluation is needed to quantify the effects
of high temperature on both the male (anther, pollen
growth and development) and female (ovule growth
and development).
• Heat-tolerance will be beneficial even in today’s
environment, and will be needed more in a warmer
future climatic conditions.
6
High Temperature Injury
Temperature and CO2 – Rice Growth
High Temperature Injury
Temperature and CO2 – Rice
12
12
330 ppm
660 ppm
330 ppm
660 ppm
10
Rice yield, t ha-1
Biomass, g plant-1
10
8
6
4
8
6
4
2
2
20% more at 660 than at 330
0
20
22
24
26
28
30
Temperature, °C
32
34
0
20
36
Baker and Allen, 1993
22
24
26
28
30
Temperature, °C
32
34
36
38
Baker and Allen, 1993
High Temperature Effects on Rice Fertility
Rice
High Temperature Effects on Rice Fertility
Cooling degree
days are
calculated based
air temperatures
and with a base
temperature of 22
°C: 22 – mean
temperature
High Temperature Effects on Rice Yields
Rice Growing Areas – Weather Stations (67 locations)
-
14
Grain Yield, Mg ha
-1
12
Baker et al.,1993
CO2, µl l
-1
10
300
8
700
6
4
2
0
20
22
24
26
28
30
32
34
36
38
Temperature, °C
7
High Temperature Injury
Temperature and CO2 Interactions – Sorghum
Growing season temperatures from those locations listed in
the previous slide and with an additional 5°C added to those
temperatures relative to optimum and marginal conditions
Seed Weight and Seed-set
Seed weight, g plant-1
From the data presented in Slide 16, we can estimate
Ambient temperature: 25.36°C = 8.26 Mg/ha
Ambient plus 5°C: 30.36°C = 5.51 Mg/ha, 33%
Temperature, °C
35
30
25
20
-1
-1
700 µmol CO2 mol
700 µmol CO2 mol
-1
350 µmol CO2 mol
30
Seed-set, %
40
24
18
12
-1
350 µmol CO2 mol
100
75
50
25
6
0
0
32/22
36/26
40/30
44/34
32/22
Air temperature (°C)
36/26
40/30
44/34
Air temperature (°C)
15
Sites
High Temperature Injury
Temperature and CO2 Interactions – Dry Beans
50
25
0
100
700 µmol CO 2 mol
350 µmol CO 2 mol
-1
75
50
(a)
07
00
08
00
09
00
10
00
11
00
12
00
13
00
14
00
0
Time of the day (h)
• Elevated temperature decreased pollen longevity.
• Elevated CO2 had no effect.
Total Weight and Seed Weight
• Elevated temperatures
decreased total dry weights
and seed yields.
30
20
10
20
(b)
• Elevated CO2 increased seed
yields but to a lesser extent at
high temperatures.
15
10
5
0
28/18 31/21 34/24 37/27 40/30
Air temperature (day/night, °C)
Prasad et al. 2005
High Temperature Injury
Temperature and CO2 – Groundnut
Prasad et al. 2005
High Temperature Injury
Temperature and CO2 – Rangeland C4 Grass – Big Bluestem
Total Weight and Seed Weight
Vegetative Weight and Seed Weight
-2
400
2
2
2
2
y = -3995 +224x -2.62x ; r = 0.96
y = -3600 +209x -2.62x ; r = 0.96
200
700 µmol CO2 mol
-1
350 µmol CO2 mol
-1
0
32/22
(d
ti
36/26
40/30
44/34
Air temperature (°C)
i
/ i htti
i i
2
2
2
300
200
100
360 ppm
720 ppm
y = -774 +78.9x -1.38x ; r = 0.98
400
700 µ mol CO2 mol
-1
350 µ mol CO2 mol
-1
0
32/22
36/26
5
2
y = -591 +75.6x -1.38x ; r = 0.99
40/30
44/34
Air temperature (°C)
Harvest, index, seed size, shelling percentage, seed-set, pollen
viability and seed number did not change between CO2 levels,
but drastically reduced with increase in temperatures.
Prasad et al. 2005
Vegaetative biomass, g plant
600
500
-1
-2
800
Seed yield (g m )
50
Vegaetative
40
-1
1.5% °C
4
-1
Vegetative dry weight (g m )
-1
350 µmol CO 2 mol
-1
700 µmol CO 2 mol
0
25
Time of the day (h)
40
30
3
20
2
10
0
15
Reproductive
-1
8.4% °C
20
25
30
Temperature, °C
35
Seed weight, g plant
75
(b) 36/26°C
-1
350 µmol CO2 mol
-1
-1
Seed yield (g plant )
100
700 µmol CO2 mol
In-vitro pollen germination
(%)
(a) 32/22°C
-1
07
00
08
00
09
00
10
00
11
00
12
00
13
00
14
00
In-vitro pollen germination
(%)
-1
Pollen Germination
Total dry weight (plant )
High Temperature Injury
Temperature and CO2 Interactions – Sorghum
1
0
40
Kakani and Reddy, 2006
8
Temperature Effects on Crop Yield
High Temperature
Several Major Crops
Effects on Growth Stages of Major Crops
Crop
Topt,
°C
Tmax,
°C
Yield
at Topt,
t/ha
Yield Yield at % decrease
32°C (28 to 32 °C)
at 28
°C, t/ha
t/ha
Rice
25
36
7.55
6.31
2.93
54
Soybean
28
39
3.41
3.41
3.06
10
Dry bean
22
32
2.87
1.39
0.00
100
Peanut
25
40
3.38
3.22
2.58
20
Grain
sorghum
26
35
12.24
11.75
6.95
41
4-week old cotton seedlings
Allen et al., 2000
High Temperature Injury
Conclusions – Temperature and CO2 Interactions
• There are no beneficial effects of elevated CO2 on
reproductive processes.
• There are no beneficial interaction of CO2 on
temperature effects on reproductive processes and
yield.
Plant Responses to Extreme Environments
Chilling and Freezing Temperature Injury
• Negative effects of elevated temperature on seed set,
seed yield and harvest index were greater at elevated
CO2 (grain sorghum, dry bean and big blue stem).
Climate Change and Crop Productivity
Conclusions – Temperature and CO2 Interactions
• There are no beneficial effects of elevated CO2
on reproductive processes in the crops investigated
(cotton, soybean, rice, sorghum and beans).
• There are no beneficial interaction of temperature on
UV-B effects on reproductive processes.
• High temperatures and higher UV-B aggravated the
damaging effect on many reproductive processes.
• Elevated CO2 did not ameliorate the damaging effects of
either higher temperatures or elevated UV-B levels.
Low Temperature Injury
Chilling and Freezing stress
• Sensitive plant species are injured by chilling at
temperatures (10 to15°C) that are too low for normal
growth but not low enough for ice to form.
• Typically, tropical or subtropical species (crops such as
maize, beans, rice, tomato, cucumber, sweet potato,
cotton, and ornamental such as Coleus, Pasiflora etc.)
are susceptible to chilling injury.
• Typical symptoms include:
- Growth is slowed
- Discoloration on foliage
- Leaves appear as if they are soaked in water
- If roots are chilled, then plants may wilt.
9
Low Temperature Injury
Chilling and Freezing stress
Low Temperature Injury
Chilling and Freezing stress
• Physiological changes: Membrane properties change in
response to chilling injury:
- Inhibition of photosynthesis
- Inhibition of carbohydrate translocation
- Slower respiration rates
- Inhibition protein synthesis
- Increased degradation of existing proteins
- Solutes leak
• Plants will synthesize more unsaturated fatty acids
(more double bonds), at least, in the chill-resistant
plants. Also, more of the simple sugars such as sucrose
will be formed under chilling.
Low Temperature Injury
Freezing stress
Percent weight of total fatty acid content
Palmitic (16:0)
Chill-resistant
species Cauliflower
21.3
28.3
Steric (18:0)
1.9
1.6
Major fatty acid
Oleic (18:0)
7.0
4.6
Linoleic (18:2)
16.4
54.6
Linolenic (18:3)
49.4
6.8
Ratio of unsaturated to 3.2
saturated fatty acids
2.1
Multiple Abiotic Factors and Crop Productivity
• Freezing (<0°C) kills plants by forming intracellular
ice crystals or by dehydrating the protoplast.
• The ability of plants to tolerate freezing temperatures
under natural conditions varies greatly among chillresistant plants.
• Continued exposure to freezing temperatures may lead
to death of the plants.
• Some freeze-resistant plants may synthesize antifreeze
proteins, which will bind to the surfaces of ice crystals
and prevent or slow down further crystal growth.
UV-B Radiation and Temperature
Cotton Reproductive Growth and Development
Effects of Multiple
Abiotic Factors
UV-B Radiation and Temperature
Cotton Reproductive Growth and Development
24/16 °C
30/22 °C
36/28 °C
120
30/22
36/28
40
30/22
30
20
36/28
10
Bolls and squares, no. plant-1
-2
Photosynthesis, µmol m s
-1
60
50
Chill-sensitive
species - maize
100
Bolls and Squares
24/16 °C
30/22 °C
36/28 °C
80
60
40
20
0
0
7
14
UV-B Radiation, kJ m-2 d-1
0
0
7
14
UV-B Radiation, kJ m-2 d-1
10
UV-B Radiation and Temperature
Cotton Reproductive Growth and Development
UV-B Radiation and Temperature
Cotton Reproductive Growth and Development
Bolls Produced
Retained Bolls
36/28
40
24/16 °C
30/22 °C
36/28 °C
30/22
30
Retained bolls, no. plant-1
30/22
Bolls produced, no. plant-1
40
20
36/28
10
0
0
7
24/16 °C
30/22 °C
36/28 °C
30
20
10
0
14
0
UV-B Radiation, kJ m-2 d-1
7
14
UV-B Radiation, kJ m-2 d-1
UV-B Radiation and Temperature
Cotton Reproductive Growth and Development
UV-B Radiation and Soybean Genotypes
Reproductive Growth and Development
Treatments
Pollen
30/22
Pollen germination
no. anther-1
%
180-210
192
70
Growing Conditions and Treatments:
Temperature (°C)
30/22
36/28
50-80
70
CO2 (ppm)
UV-B (kJ m-2 d-1)
360
0
5
1
38/30
720
10
15
UV-B and Temperature
Soybean Reproductive Development – Sensitive Cultivar
Control
+UV-B
Crop Traits and Genetic Variability to Abiotc Stresses
+T
+T+UV-B
Genotypic Variability to
Abiotic Stresses
11
Crop Traits and Genetic Variability to Abiotc Stresses
• Morphological parameters:
9 Leaf shape and lobation
9 Leaf angle
9 Root growth – length and density
Crop Traits and Genetic Variability to Abiotc Stresses
• Physiological parameters:
9
9
9
9
9
9
• Biophysical parameters:
9 Canopy temperatures, canopy temperature
depression, canopy and air temperature differential,
crop water stress index, etc.
•
• Seed-based parameters:
Remote sensing parameters:
9 Seed germination percentage and germination rate
9 Cardinal temperatures – seed germination and seed
germination rate
9 Looking at biophysical parameters (temperature) and
crop chemistry and physiology (Water, pigment and
chemical signals)
Crop Traits and Genetic Variability to Abiotc Stresses
• Reproductive parameters:
Stomata conductance
Photosynthesis, respiration, and fluorescence
Specific leaf area/weight
Cell membrane thermostability (CMT)
Chlorophyll stability index (CSI)
Carbon isotope discrimination (13C:12C ratio)
Traits and Abiotic Stress Tolerance
Physiological Parameters - Stomata Conductance and Yield
9 Pollen viability, pollen germination, pollen tube
length responses to abiotic factors.
9 Cardinal temperatures – pollen germination and
pollen tube length responses.
9 Fruit and seed set
9 Yield
• Molecular tools:
9 Currently whole host of molecular tools are
available for breeding purposes, QTL’s and marked
assisted breeding strategies.
0.0
70
-0.5
60
50
40
30
20
10
0
Bla
c
ea
kP
rl
C
t
d
h
w
ili
ta
er
sa
ile
ria
Ho
Re
llo
la s
ga
Ch
du
ng
mb
iss
ai
Ye
rie
eF
Sa
res
Me
illy
eE
Th
dM
Va
rpl
su
lsa
Ch
siv
Re
ea
Pu
Sa
plo
Tr
Ex
co
ali
Th
ai
Ho
t
Tr
ea
su
re
s
R
Va
ed
rie
ga
ta
Ye
llo
w
Sa
ng
ria
Sa
ls
a
is
si
le
M
R
ed
Pu
rp
le
Ch
ill
y
Pe
ar
l
80
C
al
ic
o
B
la
ck
90
Canopy temperature depression, °C
Cell membrane thermostability, %
100
Fl
as
h
Traits and Abiotic Stress Tolerance
Physiological Parameters – Canopy Temperature Depression
Genotypic Variability - Ornamental Pepper Cultivars
C
hi
li
Ex
pl
os
iv
e
Em
M
ed
be
us
r
a
Traits and Abiotic Stress Tolerance
Physiological Parameters – Cell Membrane Thermostability
Genotypic Variability - Ornamental Pepper Cultivars
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
-4.5
-5.0
Cultivar
Cultivars
12
Traits and Abiotic Stress Tolerance
Traits and Abiotic Stress Tolerance
Seed-based Parameters – Genotypic Variability
Ornamental Peppers
Physiological Parameters – Chlorophyll Stability Index
Genotypic Variability - Ornamental Pepper Cultivars
50
45
100
• Greater variability for
cardinal temperatures among
ornamental pepper cultivars.
40
Temperature, °C
80
70
60
Maximum seed germination
35
30
25
20
15
50
Cardinal
Temperature
10
5
40
45
30
40
20
Temperature, C
Chlorophyl stability index, %
90
10
0
k
ac
Bl
Pe
l
ar
o
lic
Ca
i
Ch
lli
Ch
y
ill
e
iv
os
pl
Ex
r
a
h
w
le
be
si
us
as
llo
is
Fl
ed
Em
Ye
M
le
M
a
d
rp
ls
Re
Pu
Sa
ng
Sa
ria
Th
t
Ho
ai
s
re
su
ea
Tr
d
Re
ta
ga
rie
Va
Seed germination rate
35
30
25
20
1
2
3
Traits and Abiotic Stress Tolerance
40
30
Topt
4
70
• Greater variability for
cardinal temperatures among
switch grass genotypes.
10
Cardinal
Temperature
Tmin
0
(B)
Tmax
50
40
30
Topt
20
10
SGR
(mean)
Tmin
8.08
11.3
Topt
26.58
33.12
Tmax
45.09
46.01
2
4
6
8
10
Genotypes
12
14
42.5
43.0
6
7
8
9
10
11
12
13
Cotton
DP 458 B/RR
NuCOTN 35B
60
50
40
30
20
10
15
20
16
25 30 35 40 45 50
Kakani et al., 2005
Temperature, °C
Temperature – Pollen Germination - Groundnut
Traits and Abiotic Stress Tolerance
Reproductive parameters – Pollen Germination
Genotypic Variability - Soybean
100
5
0
10
Tmin
0
Susceptible
Moderate
Tolerant
80
ICGV 92116
ICGV 92118
%
55-437
70
Soybean
STALWART
PI471938
DG 5630RR
80
Germination, %
0
MSG
(mean)
Pollen germination (%)
Temperature (°C)
20
27.7
Tmax
Traits and Abiotic Stress Tolerance
Pollen germination, %
Tmax
15.3
24.0
Reproductive Parameters – Pollen Germination
Genotypic Variability - Cotton
(A)
Upland
10.1
Topt
Cultivars
Seed-based Parameters – Genotypic Variability
Switchgrass Genotypes
Lowland
Tmin
10
0
50
SGR
(mean)
15
Cultivar
60
MSG
(mean)
60
40
Tb
Topt
Tmax
40 13.8 26.5 38.5
51.5 11.7 30.6 40.7
70.3 11.9 31.9 45.2
60
50
40
30
20
10
20
0
10
0
10
15
20
25
30
35
40
45
50
Temperature (°C)
20
30
Temperature, °C
40
50
Salem et al., 2006
Effect of temperature on percentage pollen germination of susceptible
(Topt < mean-LSD), moderately tolerant (Topt = mean±LSD) and tolerant
(Topt > mean+LSD) genotypes. Symbols are observed values and lines
are fitted values.
Kakani
et al., 2002
13
Temperature – Pollen Tube Growth - Groundnut
Length Tb
16
Tmax
1280 16.0 36.4 45.5
1080 15.3 30.5 37.7
1410 14.5 37.6 45.1
14
12
Pollen tube length (102 m m)
Topt
Traits and Abiotic Stress Tolerance
10
8
6
4
2
Reproductive parameters – Pollen Germination - Genotypic
Variability
Cardinal temperatues, °C
ICGV 92116
ICGV 92116
55-437
0
10
15
20
25
30
35
40
45
50
Cotton
43.3 °C
Tmax
30.4 °C
Topt
15.1 °C
Tmin
0
Kakani et al., 2002
5
10
Genotypes
15
Kakani et al., 2005
Traits and Abiotic Stress Tolerance
Traits and Abiotic Stress Tolerance
Reproductive parameters – Pollen Germination
Genotypic Variability
Reproductive parameters – Pollen Germination
Genotypic Variability
55
50
45
40
35
30
25
20
15
10
5
Soybean
47.2 °C
Tmax
30.2 °C
Topt
13.3 °C
Tmin
0
5 10 15 20 25 30 35 40 45 50
Salem et al., 2006
Genotypes
Cardinal temperatues, °C
Cardinal temperatues, °C
Temperature (°C)
55
50
45
40
35
30
25
20
15
10
5
55
50
45
40
35
30
25
20
15
10
5
Groundnut
43 °C
0
5
Tmax
30.1 °C
Topt
14.1 °C
Tmin
10
15
Genotypes
20
Traits and Abiotic Stress Tolerance
Traits and Abiotic Stress Tolerance
Concluding Remarks
Concluding Remarks
• The influence of stress factors on reproductive
biology of crops/plants has not been well studied.
• Better screening tools/methods are needed to assess
the genotypic variability among crop species,
genotypes or lines including wild relatives of crop
species.
• Molecular tools and biotechnology will play a greater
role in the quest for knowledge and in developing
stress tolerance.
25
Kakani et al. 2002
• The current rate of climate change and climate
variability and projected changes in climate are
unprecedented, and plants may not cope with these
rapid changes.
• There is an urgent need to develop crop cultivars to a
variety of stresses (high and low temperatures, drought
tolerance, UV-B radiation stress, ozone tolerance, flood
tolerance, heavy metal tolerance, etc.
14