American International Journal of
Research in Formal, Applied
& Natural Sciences
Available online at http://www.iasir.net
ISSN (Print): 2328-3777, ISSN (Online): 2328-3785, ISSN (CD-ROM): 2328-3793
AIJRFANS is a refereed, indexed, peer-reviewed, multidisciplinary and open access journal published by
International Association of Scientific Innovation and Research (IASIR), USA
(An Association Unifying the Sciences, Engineering, and Applied Research)
Effect of drought on plant water status, gas exchange and yield parameters in
Contrasting genotypes of Tomato (Solanum lycopersicum)
Sivakumar, R.
Department of Crop Physiology,
Tamil Nadu Agricultural University, Coimbatore - 641 003, Tamil Nadu
Abstract: Effect of drought stress on plant water status, gas exchange and yield parameters of tomato
(Solanum lycopersicum) genotypes was investigated under pot culture conditions in rainout shelter. The drought
condition was created at first day after transplanting based on field capacity of soil. Experiment was laid out
with 18 genotypes by adopting CRD with three replications and two treatments viz, 100 and 50% field capacity.
As the stress increased from 100% field capacity to 50% field capacity, reductions in leaf water potential,
relative water content, transpiration rate and photosynthetic rate were noticed at all the growth stages. The
genotypes LE 114,
LE 57, LE 118 and LE 27 which showed significantly less reduction in the above
parameters during drought were considered as drought tolerant. Higher flower abscission was recorded in LE
20 and LE 1 under drought. Genotypes LE 1, LE 3, LE 5, LE 100 and LE 20 which recorded the lowest leaf
water potential, RWC and photosynthetic rate and ultimately poor yield were considered as drought susceptible.
Key words: Drought, leaf water potential, RWC, transpiration rate, flower abscission, yield
I. Introduction
Drought stress is one of the serious environmental factor affecting plant growth, development, yield and quality. It
induces various physiological and biochemical adaptations in plants. It has been estimated that up to 45% of the world
agricultural lands are subjected to drought (Bot et al., 2000). Water deficit leads to the agitation of most of the
physiological and biochemical processes and consequently reduces plant growth and yield (Boutraa, 2010). Many
authors reported that water deficit reduces the rate of photosynthesis in plants (Cornic, 2000). Leaf water potential
(LWP) has been suggested as selection criteria for improving drought tolerance. LWP is recognized as an index for
whole plant water status (Turner, 1982) and maintenance of high LWP is considered to be associated with
dehydration avoidance mechanisms (Levitt, 1980). The productivity of the crop may be related to physiological
attributes like transpiration rate, photosynthetic rate, relative water content (RWC) and LWP. Higher RWC indicates
better growth and development, which in turn depends on leaf area. Rapid early growth and maintenance of RWC at
reasonably higher level during reproductive phase greatly influences the yield (Haloi and Baldev, 1986).
The adaptive potential of some plant species reducing water losses were achieved by closing of stomata and
reduction in the transpiration rate (Tardieu and Davies, 1996). Hence, measurement of transpiration rate is an
excellent tool to assess drought tolerant capacity of crop plants. However, reduction of transpiration rate under
drought causes increment of leaf temperature is deleterious effect for plants. Abscission of reproductive organs like
flower buds and flowers is a major yield limiting factor in vegetable crops (Wien et al., 1989). The abscission of
floral organs during stresses has been associated with the changes in physiological processes (Aloni et al.,
1996). In tomato, where the abscission of flowers and flower buds and the reduction in photosynthesis was more
in susceptible cultivars compared to the tolerant cultivars where the abscission was relatively less (Bhatt et al.,
2009).
Tomato (Solanum lycopersicum) is one of the most popular and widely grown vegetables in the world. Considering
the potentiality of this crop, there is plenty of scope for its improvement, especially under the drought situation.
Drought stress is one of the severe environmental issue affecting plant growth, development and yield. Although the
concept of drought tolerance has been viewed differently by molecular biologist, biochemist, physiologists and
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Sivakumar, American International Journal of Research in Formal, Applied & Natural Sciences, 8(1), September-November, 2014, pp. 57-62
agronomists, the major concern is to enhance the biomass and yield under limited input of water, which is a
characteristic feature of rainfed agriculture. There are several physiological and biochemical traits contributing to
the drought tolerance of horticultural crops. However, large number of tomato genotypes have not been screened for
drought tolerance or exploited for their cultivation under drought situation. To breed drought tolerant genotypes, it is
necessary to identify physiological traits of plants, which contributes to drought tolerance. Therefore, the present
investigation was carried out to study the physiological traits to facilitate the screening and selection of tomato
genotypes for drought tolerance.
II. Materials and Methods
The present study was undertaken to study the effect of drought on gas exchange and physiological parameters in
tomato genotypes in pot culture at Rainout Shelter of Crop Physiology Department, Tamil Nadu Agricultural
University, Coimbatore, Tamil Nadu during 2011–12. The experiment was conducted with 18 tomato genotypes viz.,
LE 1, LE 3, LE 5, LE 13, LE 14, LE 18, LE 20, LE 23, LE 27, LE 57, LE 100, LE 114, LE 118,
LE 125, CO 3,
PKM 1, TNAU THCO 3 and COTH 2 and two treatments viz., 100% FC and 50% FC with three replications. Seeds
of selected genotypes were sown in trays filled with vermicompost for nursery. Uniform size (38 cm width and 32 cm
height) pots were filled with 25 kg of soil and saturated with water and the field capacity of the soil was recorded.
Twenty-five days old seedlings were transplanted and one plant was maintained in each pot. Drought was imposed at
first day after transplanting onwards by maintaining soil moisture at 50% field capacity for drought stress by
weighing and watering each pot at regular interval. Crop was supplied with fertilizers and other cultivation operations
including plant protection measures as per recommended package of practices of Tamil Nadu Agricultural University,
Coimbatore. All the observations were recorded on third leaf from top at 30, 60 and 90 DAT. The experiment was
laid out in completely randomized block design with three replications.
A. Estimation of plant water status
Leaf water potential was measured by using an instrument Leaf Water Potential Meter (ARIMAD 3000) and expressed
as MPa. The relative water content (RWC) was estimated according to Barrs and Weatherly (1962). Fifty uniform leaf
discs were used and fresh weight (Fw) was recorded. The leaf discs were floated in water for one hour to attain full
turgid and turgid weight (Tw) was recorded. Then the leaf discs were kept in hot air oven at 80°C for 48 hours and
the dry weight (Dw) was recorded. The relative water content (RWC) was calculated by using following formula
RWC = [(Fresh weight – Dry weight) / (Turgid weight – Dry weight)] X 100
B. Measurement of gas exchange parameters
Gas exchange parameters like transpiration rate, leaf temperature and photosynthetic rate were determined by a
portable photosynthesis system (Model LI-6400 of LICOR inc., Lincoln, Nebraska, USA) equipped with a halogen
lamp (6400-02B LED) positioned on the cuvette. Three measurements were taken in the same leaf. Leaves were
inserted in a 3 cm2 leaf chamber and PPFD at 1200 µmol photons m-2 s-1, and relative humidity set at 50-55%.
C. Estimation of yield parameters
Flower abscission study was conducted on single flower basis. Flower number of each plant and dropped flower per
each pot were counted every 3 days once. These records were used to calculate the flower abscission and expressed in
terms of percentage. The fruit weight per plant was recorded in control and stressed plants in each picking and fruit
yield (kg per plant) was calculated as fresh weight of fruits in all the pickings.
D. Statistical analysis
The data on various parameters were analyzed statistically as per the procedure of Gomez and Gomez (1984).
III. Results and Discussion
Tomato genotypes responded differentially to water deficit stress in the form of changes in various physiological
processes. LWP is an indicator of plant water status. Significantly higher LWP was observed at 100% field
capacity than 50% FC and also early stage of crop growth (30 DAT) recorded higher LWP than later stage (Table
1). Among the genotypes, LE 118 recorded high water potential (-1.03) followed by LE 114 (-1.05), LE 57 (-1.19)
and LE 27 (-1.21), while LE 125 (-1.52) recorded lowest LWP at 50% FC condition during 60 DAT. During water
deficit stress, the genotype, which maintains high LWP, is considered as drought tolerant. Eureka Teresa et al.
(2000) reported that the reduction of soil field capacity from 100 to 57% resulted in a sharp decline in LWP by
50%. Decrease in LWP induces an osmoregulatory mechanism through the accumulation of some primary and
secondary metabolites, such as carbohydrates, amino acids, amides, sugar alcohols and salt cations (Ashraf and
Foolad, 2007). Leaf water potential in the water deficit treatment was lower than in the control plants in oil palm
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was observed by Suresh et al. (2012). Relative water content decreased under water deficit stress. RWC also
showed a decreasing trend from 30 DAT towards maturity. Among the genotypes, LE 118 (68.62), LE 57 (67.89),
LE 27 (65.62) and LE 114 (64.83) recorded the highest RWC, while LE 1 (45.74), LE 20 (48.81) and LE 3 (48.97)
recorded the lowest RWC at 50% FC at 60 DAT (Table 1). Among the genotypes, LE 27 showed comparatively
less reduction (10%) in RWC at 50% FC, followed by LE 57 (10.96%), LE 114 (12%) and LE 118 (12.4%).
Genotypes, which showed higher RWC ensure more favourable internal water relations of tissue and showed better
drought tolerance capacity. Similar results were reported earlier by Srinivas Rao and Bhatt (1992) in tomato.
Transpiration is important trait for assessment of drought tolerance, and is widely affected by environmental stress
conditions. Higher transpiration rate were observed in control plants (100% FC) at all the stages compared to water
deficit stress condition (50% FC) in all the genotypes (Table 2). Among the genotypes, LE 100 (5.20) recorded the
lowest transpiration rate, followed by LE 20 (5.52), LE 1 (6.10) and LE 125 (6.15) at 50% FC. LE 57 (9.68)
showed high transpiration rate during water deficit condition, followed by LE 118 (8.93), LE 27 (8.57) and LE 114
(7.97). The response of plants with reduction in transpiration rate, suggests water conservation from stomatal
closure and reduced loss of water through stomata (Jones et al., 1985). However, reduced water loss by stomatal
closure leads to increment of leaf temperature which is deleterious effect to the plant system. In the present study,
lowest transpiration rate genotypes LE 100 and LE 20 showed higher increment percent of 7.8 and 7.07 leaf
temperature under drought at 60 DAT. While, moderately maintain the transpiration rate under drought showed
less increment of leaf temperature was recorded in the genotypes LE 118 (2.84) and LE 57 (4.29) (Fig. 1).
Meenakumari et al. (2004) observed that as transpiration rate decreased under severe stress, leaf temperature
increased by 2-4ºC. Hence, increment of leaf temperature under drought is most dangerous than water loss. Under
water limiting condition, genotypes maintaining transpiration rate may be regarded as drought tolerant. Among the
genotypes, the raise in leaf temperature was less in LE 118 and LE 57 due to drought stress and this condition is
associated with maintenance of high rate of transpiration. This finding is in agreement with the results of Tan
(1993) in tomato. The less increment of leaf temperature in the tolerant genotypes might be due to the high
transpiration rate under drought which helps to reduce the heat load and escape from drought induced high
temperature stress. The genotypes LE 100 and LE 20 showed higher leaf temperature by less transpiration leads to
ultimate problem of ROS production and membrane damage may be the reason for lesser yield considered as
drought susceptible.
The photosynthetic rate in 100% FC plants was significantly higher than 50% FC plants and it was increased up to
60 DAT and reduced at 90 DAT (Table 2). Highest photosynthetic rate (39.76) under 100% FC was observed in
TNAU THCO 3 at 60 DAT. Results indicated that water deficit stress inhibited photosynthetic rate in tomato
genotypes. Reduction in photosynthetic rate under drought stress has been related to stomatal limitation due to
stomatal closure (Rodrigues et al., 1993). Irrespective of all the stages, performance of genotypes across the
treatment showed that, genotypes LE 118, LE 57, LE 114 and LE 27 recorded higher photosynthetic rate, while the
lower rate was observed in LE 100, LE 20, LE 1 and LE 23. At 50% FC, LE 118 recorded highest photosynthetic
rate (31.84), followed by LE 57 (29.41), LE 114 (27.69) and LE 27 (27.22). These results are in conformity with
findings of Pirjo et al. (1999) in tomato and turnip, Silk and Fock (2000) in tomato. Rao et al. (2000) reported a
significant decline in the rate of photosynthesis, transpiration and stomatal conductance in tomato cultivars under
drought. Rahman et al. (1999) reported the decline in photosynthesis and transpiration under water stress in both
tolerant and sensitive cultivars. Maintenance of transpiration and photosynthetic rate under unfavorable
environmental condition like drought is important trait for tolerance and also maintaining the yield is observed in the
present study in LE 118 genotype. Drought induced high temperature stress is one of the most important causes of
change in plant morphology, physiology and biochemical aspects, which reduces plant growth and development. In
the present study, drought increased the flower abscission over control in all the genotypes at various levels.
However, the less flower drop percentage was noticed in the genotypes LE 118 (11.7%), LE 57 (12.3%) and LE
114 (12.7%). But the genotypes, LE 20, LE 1and LE 23 showed their inferiority with higher flower abscission per
cent (Fig. 2). An earlier finding of Bhatt et al. (2009) in tomato strongly supports the results of the present study.
Lower flower abscission in the tolerant genotypes might be due to the maintenance of photosynthesis and efficient
translocation of photosynthates to the reproductive parts under drought. The reduction in photosynthesis during
stress may decrease the availability of assimilates to the developing floral organs and leads to the abscission of
flowers and flower buds in susceptible cultivars. However, some workers are of the opinion that the abortion of
reproductive organs is not solely due to a shortage of assimilate supply but also due to other factors such as
assimilate utilization (Ruiz and Guardiola, 1994; Aloni et al., 1996). Drought induced high temperature also cause
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Sivakumar, American International Journal of Research in Formal, Applied & Natural Sciences, 8(1), September-November, 2014, pp. 57-62
bud and flower drop up to 42.56% in the tomato (Srivastava et al., 2012). Fruit yield showed significant differences
among the genotypes and treatments. Decrease in fruit yield was observed at 50% FC level compared to 100% FC.
LE 114 recorded higher fruit yield (1,372.64) followed by LE 118 (1,112.88), LE 57 (1,071.20) and LE 27 (948.96)
(Fig. 3). The percentage yield reduction under drought over control has been suggested as the most important
parameter for assessing drought tolerance than fruit yield. The highest percentage reduction in yield under drought
was recorded in LE 125 (83%), followed by LE 5 (80%), LE 23 (76%) and COTH 2 (71%). The least reduction in
fruit yield under drought was observed in LE 57 (18%), LE 114 (20.6 %), LE 27 (21%) and LE 118 (27 %).
Maintenance of fruit yield under drought by the genotypes LE 57, LE 118, LE 114 and LE 27 may be attributed to
their ability to maintain higher leaf water potential, RWC, transpiration rate and photosynthetic rate with less leaf
temperature leads reduction of flower abscission.
Table 1. Effect of drought on leaf water potential and RWC of tomato genotypes at different growth stages
Leaf water potential (- MPa)
S.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
SEd
CD
(0.05)
Genotypes
30 DAT
100%
50%
FC
FC
0.42
1.41
0.46
1.40
0.50
1.39
0.45
1.23
0.51
1.18
0.42
1.20
0.44
1.43
0.49
1.33
0.53
1.14
0.52
1.12
0.48
1.36
0.40
0.99
0.48
0.97
0.41
1.44
0.55
1.31
0.57
1.25
0.48
1.35
0.44
1.32
0.48
1.27
LE 1
LE 3
LE 5
LE 13
LE 14
LE 18
LE 20
LE 23
LE 27
LE 57
LE 100
LE 114
LE 118
LE 125
CO 3
PKM 1
THCO 3
COTH 2
Mean
60 DAT
100%
50%
FC
FC
0.46
1.48
0.51
1.46
0.53
1.47
0.46
1.30
0.53
1.24
0.46
1.27
0.48
1.50
0.54
1.41
0.58
1.21
0.55
1.19
0.54
1.44
0.44
1.05
0.53
1.03
0.45
1.52
0.60
1.38
0.62
1.32
0.53
1.42
0.50
1.39
0.52
1.34
Relative water content (%)
90 DAT
100%
50%
FC
FC
0.49
1.59
0.62
1.54
0.55
1.55
0.57
1.37
0.64
1.33
0.57
1.32
0.69
1.58
0.65
1.50
0.59
1.28
0.56
1.26
0.65
1.52
0.47
1.11
0.58
1.00
0.56
1.68
0.66
1.50
0.68
1.45
0.64
1.49
0.61
1.47
0.60
1.42
30 DAT
100%
50%
FC
FC
68.22
54.74
68.20
54.97
65.89
54.67
71.16
59.38
68.90
58.10
70.61
58.93
64.87
52.81
66.50
53.68
72.20
61.62
72.33
61.89
67.79
55.17
71.61
62.83
74.13
64.62
68.04
54.63
71.88
57.01
70.35
57.45
67.75
54.68
68.81
53.85
69.40
57.30
60 DAT
100%
50%
FC
FC
68.22
45.74
71.20
48.97
70.89
49.67
73.16
52.38
68.90
52.10
70.61
58.93
64.87
48.81
66.50
51.68
72.20
65.62
75.33
67.89
67.79
52.17
72.61
64.83
77.13
68.62
68.04
51.63
71.88
59.01
70.35
57.45
67.75
54.68
68.81
53.85
70.35
55.78
90 DAT
100%
50%
FC
FC
58.20
39.50
60.18
42.04
62.94
48.69
70.06
58.37
68.86
53.95
70.52
62.78
61.95
43.91
64.53
52.77
71.07
63.57
70.19
64.87
64.79
50.23
70.49
62.76
71.94
65.59
59.03
48.70
69.75
54.04
66.27
56.47
65.75
53.75
66.78
49.93
66.29
54.00
G
0.03
T
0.01
GxT
0.04
G
0.03
T
0.01
GxT
0.04
G
0.03
T
0.01
GxT
0.04
G
1.67
T
0.56
GxT
2.36
G
1.62
T
0.54
GxT
2.29
G
1.55
T
0.52
GxT
2.19
0.06*
0.02*
0.08
0.06*
0.02*
0.08
0.06*
0.02*
0.09
3.33*
1.11*
4.71
3.24*
1.08*
4.58
3.10*
1.03*
NS
DAT – Days after transplanting; FC – Field capacity
Table 2. Effect of drought on gas exchange parameters of tomato genotypes at different growth stages
Transpiration rate (mmol H2O m-2 s-1)
S. No. Genotypes
1
2
3
4
5
6
7
8
9
10
11
LE 1
LE 3
LE 5
LE 13
LE 14
LE 18
LE 20
LE 23
LE 27
LE 57
LE 100
Photosynthetic rate (µmol CO2 m-2 s-1)
30 DAT
60 DAT
90 DAT
30 DAT
60 DAT
90 DAT
100% FC 50% FC 100% FC 50% FC 100% FC 50% FC 100% FC 50% FC 100% FC 50% FC 100% FC 50% FC
9.15
6.92
9.25
6.10
6.38
5.01
28.24
13.67
36.54
18.83
18.00
7.95
8.28
6.16
9.56
6.28
6.57
5.32
25.16
16.20
31.09
19.03
18.59
7.15
8.15
6.07
9.41
6.40
6.43
5.23
24.81
15.97
34.65
18.98
23.05
9.10
9.60
7.00
11.08
7.23
7.94
5.15
22.35
13.39
32.69
21.91
23.15
11.99
9.50
7.07
10.97
7.99
7.84
5.23
27.97
18.01
36.21
23.84
24.56
12.89
9.98
6.88
11.52
8.06
8.34
5.03
29.58
17.04
39.21
26.48
24.96
15.75
8.10
6.58
8.80
5.52
6.34
5.71
23.13
12.89
31.06
17.02
21.56
7.17
7.88
6.57
9.10
6.05
6.15
5.70
23.67
15.24
30.43
16.67
20.95
7.82
9.45
7.48
10.91
8.57
6.79
5.66
26.13
20.82
35.08
27.22
25.47
15.26
9.10
7.72
11.66
9.68
8.47
6.52
28.33
21.88
38.03
29.41
27.33
18.33
7.95
5.92
9.18
5.20
6.22
5.07
24.10
13.52
32.35
15.72
22.82
8.86
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12
13
14
15
16
17
18
SEd
CD
(0.05)
LE 114
LE 118
LE 125
CO 3
PKM 1
THCO 3
COTH 2
Mean
9.09
9.28
8.45
8.80
9.10
10.50
10.25
9.03
7.91
8.35
6.29
6.55
6.77
7.82
7.63
6.98
10.65
10.87
9.75
10.16
10.51
12.12
11.83
10.41
7.97
8.93
6.15
7.18
7.53
9.02
8.37
7.35
8.46
8.66
6.74
7.11
7.43
8.88
8.62
7.41
5.63
6.78
5.40
4.67
4.91
6.02
5.82
5.49
29.75
28.49
29.25
27.25
26.00
30.87
31.55
27.04
19.15
23.63
14.26
17.54
15.74
17.88
17.67
16.92
37.26
36.59
38.90
36.58
34.91
39.76
37.50
35.49
27.69
31.84
18.57
23.04
22.13
21.24
20.27
22.22
24.58
27.85
24.32
26.92
25.30
24.04
25.32
23.82
16.41
18.69
8.70
13.10
13.20
12.33
11.37
12.00
G
0.21
T
0.07
GxT
0.29
G
0.23
T
0.08
GxT
0.33
G
0.16
T
0.05
GxT
0.23
G
0.57
T
0.19
GxT
0.80
G
0.74
T
0.25
GxT
1.05
G
0.47
T
0.16
GxT
0.66
0.41*
0.14*
NS
0.45*
0.15*
NS
0.32*
0.11*
NS
1.13*
0.37*
1.59*
1.48*
0.49*
2.09*
0.93*
0.31*
1.32*
DAT – Days after transplanting; FC – Field capacity
Fig 1. Effect of drought on leaf tempearture (°C) of tomato genotypes
Fig 2. Effect of drought on flower abscission (%) of tomato genotypes
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Sivakumar, American International Journal of Research in Formal, Applied & Natural Sciences, 8(1), September-November, 2014, pp. 57-62
Fig 3. Effect of drought on fruit yield (g plant-1) of tomato genotypes
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