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Root characteristics, plant water status and CO2 exchange in relation to drought
tolerance in chickpea
Neeraj Kumar, AS Nandwal*, Sarita Devi, KD Sharma, Ashok Yadav and RS Waldia
CCS Haryana Agricultural University, Hisar 125 004, Haryana, India
*Corresponding author: [email protected]; [email protected]
Citation: Kumar N, Nandwal AS, Devi S, Sharma KD, Yadav A and Waldia RS. 2010. Root characteristics, plant water
status and CO2 exchange in relation to drought tolerance in chickpea. Journal of SAT Agricultural Research 8.
Abstract
et al. 1995, Turner et al. 2001, Kumar et al. 2007). In the
rainfed environments, the depth of rooting is often cited
as an important criterion because it has a major influence
in determining the potential supply of water from the
deep soil and thus improves yield (Saxena et al. 1993,
Krishnamurthy et al. 2003, Kashiwagi et al. 2005).
The new chickpea genotypes identified could be
utilized as valuable sources in a breeding program to
develop cultivars for areas where substantial amounts of
water are left in the subsoil at maturity. The present study
was conducted to assess the chickpea genotypes for the
root system traits.
Root traits, such as rooting depth and root biomass, have
been identified as the most promising plant traits in
chickpea for terminal drought tolerance. With this
objective six genotypes of chickpea, viz, H02-36, H0356, H04-31, H04-33, H04-45 and HC-5 were assessed
for various root characteristics under two environments –
irrigated and rainfed. The sampling was done at full
bloom. Under rainfed conditions, there were significant
differences in the rooting depth among the genotypes.
The chickpea roots penetrated to a maximum depth of 80
to 121 cm. The rooting depth remained higher under
rainfed than irrigated environment. The genotypes HC-5
and H02-36 showed higher dry matter of roots, rooting
depth, root : shoot ratio, yield and better plant water
status and were directly associated with seed yield per
plant and can be used in chickpea breeding for drought
tolerance.
Material and methods
Six genotypes of chickpea, viz, H02-36, H03-56, H04-31,
H04-33, H04-45 and HC-5 were evaluated for various
root characteristics during the rabi (postrainy) season of
2007/08. The experiment was repeated in the next year
2008/09 and the pattern of results obtained was almost
similar; hence the data of one year, ie, 2007/08 is given in
this paper. The experimental material was planted in
specially constructed facilities of concrete microplots (6
m long, 1 m wide and 1.5 m deep connected with iron
gates and washing tanks) (Fig. 1) filled with sandy soil
and irrigated up to field capacity at Crop Physiology
Field Lab, Agronomy Research Farm, CCS Haryana
Agricultural University, Hisar (29°10’ N, 75°46’ E, 215
m altitude), Haryana, India. The plots were fertilized at
15 kg N ha-1 and 40 kg P2O5 ha-1 as basal dose before
sowing. The seeds were inoculated with Rhizobium
culture Ca-181.
Each genotype was sown in four rows of 1 m length
with interrow spacing of 30 cm and plant spacing of 10
cm under two environments, namely irrigated (I: two
irrigations of 6 cm depth each at flowering and pod
filling) and rainfed (R: one irrigation of 30 mm equal to
long-term average seasonal rainfall). The experiment was
conducted in a randomized complete block design
(RCBD) with three replications. The plots were kept
Introduction
Chickpea (Cicer arietinum) is an important source of
protein (17–26%) and the world’s third major coolseason food legume with a total annual production of 9.6
million tons from 11.5 million ha and an average seed
yield of 840 kg per ha-1 (FAO 2009). About 90% of the
world’s chickpea is grown under rainfed conditions
where the crop experiences terminal drought stress
during the reproductive phase resulting in heavy yield
losses of up to 3.4 million tons (Sharma 2004–05). A
large portion of the losses can be prevented through crop
improvement. Better drought adopted genotypes could
more effectively be bred when traits that confer yield
under drought stress conditions can be identified and
used as selection criteria (Ludlow and Muchow 1990,
Krishnamurthy et al. 2003, Kashiwagi et al. 2006).
Rooting depth and density are among the main
drought avoidance traits identified to confer seed yield in
chickpea under terminal drought environments (Subbarao
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water content of leaf by Weatherley’s method (1950),
osmotic potential by Vapor Pressure Osmometer (Model
5100-B, Wescor, Logan, USA), transpirational cooling,
ie, canopy temperature depression using infra-red
thermometer (Model AG-42 Tele-temp Corp, California,
USA) and the rates of photosynthesis with a portable
photosynthesis system (Infrared Gas Analyzer, CIRAS-1,
PP Systems, UK) using the third fully expanded leaf from
top, which was later sampled for leaf water status.
Yield attributes were recorded from five plant samples
taken from each plot at harvest. Seed and biological
yields were recorded from individual plants and
expressed as g plant-1. Soil moisture of 0–15 cm soil
depth was determined by gravimetric method. The soil
moisture at 15–45, 45–75, 75–105 and 105–135 cm soil
depth was recorded by Neutron Moisture Meter (Model
2651 Troxler laboratories, Raleigh, North Carolina,
USA) (Fig. 1). The observations were recorded at 20
days interval at 80, 100 and 120 DAS. Soil moisture
status for rainfed and irrigated conditions is presented in
Table 1.
Data were analyzed and treatment means were
compared by the least significant differences (LSD)
(P=0.05) test. Weather conditions during the crop season
were recorded at the Agro-meteorological observatories
of the CCS Haryana Agricultural University, Hisar.
Figure 1. (a) Microplots (side view); (b) Neutron probes;
(c) Crop view; (d, e and f) Washing of root system.
weed free by hand weeding and intensive protection
measures were taken against pod borer (Helicoverpa
armigera).
Five plants with similar growth were taken from each
replication for recording the biomass of leaves, stems,
roots and nodules at full bloom [80–100 days after
sowing (DAS)] of all the genotypes under both the
environments. Plants were taken out with roots after
thorough washing of the sand by water jet gently.
The shoot and root lengths were measured with meter
rod. The average of five plants in each replication was
determined for each treatment. The selected individual
plant in each replication of a genotype was separated into
leaf, stem, pod and root. The plant parts were dried at
80°C till constant weight was attained. The root : shoot
ratio was computed on dry weight basis.
The plant water relation parameters were also
recorded at full bloom stage, between 1000 and 1200 h.
The leaf water potential was measured by Pressure
Chamber (PMS Instrument Co., Oregon, USA), relative
Results and discussion
The chickpea genotypes differed significantly for time to
50% flower. H 04-33 took 81 days for 50% flower
compared to 94 days by HC-5 and H02-36. Plants grown
under rainfed condition flowered and matured earlier
than under irrigated condition (Table 2). There was large
variability among the genotypes for rooting depth both
under irrigated and rainfed conditions in the microplots
(Table 2, Fig. 2). The roots penetrated to a maximum
Table 1. Moisture content (%) in different layers of soil profile in microplots.
Moisture at
Sowing
80 DAS1
100 DAS
120 DAS
Treatment
Irrigated
Rainfed
Irrigated
Rainfed
Irrigated
Rainfed
Soil moisture (%) at different soil depth (cm)
_________________________________________________________________________
0–15
15–45
45–75
75–105
105–135
11.5
10.9
5.2
9.4
5.1
10.2
5.0
13.2
10.4
6.8
8.2
5.9
10.0
5.2
13.9
9.6
8.4
7.6
7.3
9.4
7.2
16.4
12.6
9.2
8.2
7.9
11.1
8.2
20.4
15.4
12.0
9.8
9.4
13.8
9.2
1. DAS = Days after sowing.
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Table 2. Plant water relation parameters and yield attributes at maturity of chickpea genotypes under irrigated (I) and
rainfed (R) conditions in microplots.
Parameters
T
HC-5
Time to 50% flower (days)
I
R
Time to maturity (days)
H02-36
H03-56
H04-33
H04-45
96.0
94.6
83.6
84.0
90.3
86.6
79.6
80.3
LSD (P=0.05), G = 2.1, T = 1.3, G × T = NS1
82.6
78.6
83.3
78.6
I
R
149.6
148.0
137.6
139.6
144.0
144.3
130.0
131.6
LSD (P=0.05), G = 2.2, T = 1.2, G × T = NS
145.6
140.0
142.3
137.3
Rooting depth (cm)
I
R
108
87
78
70
121
108
95
86
LSD (P=0.05), G = 2.3, T = 3.1, G × T = 4.2
75
80
72
91
Shoot length (cm)
I
R
67
55
64
60
62
48
53
47
LSD (P=0.05), G = 1.9, T = 2.4, G × T = 3.2
53
38
64
42
Root dry weight (g plant-1)
I
R
5.3
4.8
4.1
8.4
7.0
4.8
LSD (P=0.05), G = 0.5, T = 0.6, G × T = NS
2.4
4.3
3.0
4.6
3.6
4.1
Stem dry weight (g plant-1)
I
R
10.4
6.8
7.5
9.5
7.7
5.5
LSD (P=0.05), G = 0.4, T = 0.8, G × T = 1.0
5.5
4.9
6.3
5.3
5.8
5.1
Leaf dry weight (g plant-1)
I
R
5.8
4.4
7.0
6.8
5.9
7.5
LSD (P=0.05), G = 0.3, T = 0.4, G × T = 0.6
6.2
5.1
6.7
6.2
4.9
4.3
Nodule dry weight (g plant-1)
I
R
0.63
0.40
0.52
0.37
0.35
0.39
LSD (P=0.05), G = 0.3, T = 0.5, G × T = 0.8
0.39
0.33
0.47
0.36
0.58
0.32
Total dry weight (g plant-1)
I
R
22.13
16.40
19.12
14.49
25.07
17.95
18.19
14.63
LSD (P=0.05), G = 0.3, T = 0.5, G × T = 1.2
16.47
15.46
14.88
13.82
Root/Shoot ratio (dry weight basis)
I
R
0.47
0.86
0.62
0.80
Seed yield (g plant-1)
I
R
20.6
18.5
16.8
15.2
16.9
14.2
13.4
11.2
LSD (P=0.05), G = 0.30, T = 3.14, G × T = 3.20
17.3
13.2
14.3
12.5
Water potential (ψw) of leaf (MPa)
I
R
−0.48
−0.58
−0.56
−0.57
−0.77
−0.78
−1.25
−0.98
LSD (P=0.05), G = 0.04, T = 0.28, G × T = 0.31
−0.63
−1.08
−0.73
−1.15
Osmotic potential (ψs) of leaf (MPa)
I
R
−1.42
−1.36
−1.33
−1.22
−1.72
−1.61
−1.49
−1.40
LSD (P=0.05), G = 0.03, T = 0.14, G × T = 0.20
−1.28
−1.46
−1.24
−1.35
Relative water content (%)
I
R
92.0
89.9
88.3
86.2
82.0
82.0
80.0
72.4
LSD (P=0.05), G = 1.13, T = 3.14, G × T = 3.20
84.3
78.4
84.1
77.8
Photosynthesis (mg CO2 cm-2 h-1)
I
R
17.2
16.1
15.6
13.1
8.3
8.6
7.9
2.1
LSD (P=0.05), G = 0.05, T = 0.05, G × T = 0.14
14.2
4.1
8.8
1.4
CTD2 (°C)
I
R
4.3
4.4
3.7
0.3
1.9
1.6
1.2
−1.7
LSD (P=0.05), G = 0.03, T = 0.03, G × T = 0.08
1.8
−1.4
2.0
−0.7
0.50
0.70
0.54
0.88
0.80
0.87
LSD (P=0.05), G = 0.6, T = 0.8, G × T = 1.3
H04-31
0.43
0.87
1. G = Genotype; T = Treatment; NS = Not significant.
2. CTD = Canopy temperature depression.
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depth of 80 to 121 cm at full bloom stage under rainfed
condition. The rooting depth remained higher under
rainfed than irrigated environment. Under rainfed
condition, the roots of HC-5 and H02-36 reached a soil
depth of more than 100 cm, whereas the roots of H04-33
did not grow beyond 80 cm. Under irrigated condition,
the roots were able to grow to a maximum depth of 108
cm in HC-5 and 87 cm in H02-36.
Under rainfed condition, the moisture stress reduced
the plant height – but reverse was true for root depth –
and increased the biomass partitioning towards the roots.
Among the genotypes, root biomass per plant was high in
HC-5 and H02-36. The genotypes H04-31 and H04-33
had low root biomass per plant. At full bloom, about 34%
of the total dry matter was diverted in the roots of HC-5,
with slightly higher dry matter (39%) in H02-36 under
rainfed condition. There was a significant variation for
seed yield under rainfed condition. The genotypes HC-5
and H02-36 with deep root system were shown to
produce high shoot biomass, ie, 9.5 and 7.7 g plant-1 and
seed yield, ie, 16.9 and 14.2 g plant-1, respectively, under
rainfed condition.
The water potential (ψw), osmotic potential (ψs) and
relative water content of leaf were −0.77 MPa, −1.72
MPa and 82.0% respectively in HC-5 and −0.78 MPa,
−1.61 MPa and 82.0% respectively in H02-36, under
rainfed condition (Table 2). The photosynthetic rates
were significantly reduced by drought in all genotypes
and canopy temperature depression values were high
(Table 2). It indicates the importance of prolific and deep
root systems in keeping the canopy cooler for longer time
perhaps due to water extraction by deep rooting
(Kashiwagi et al. 2008).
The results of this study indicated that under rainfed
conditions, the genotypes HC-5 and H02-36 showed
higher dry matter of roots, rooting depth, root : shoot
ratio and photosynthetic rate, better plant water status and
cooler canopy temperature depression and these traits
were directly associated with seed yield per plant. These
genotypes could be utilized in crop improvement
programs as sources of chickpea breeding for drought
tolerance.
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Figure 2. Rooting depth of chickpea genotypes under irrigated
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