International Journal of Agricultural Science
and Research (IJASR)
ISSN 2250-0057
Vol. 3, Issue 2, Jun 2013, 137-148
©TJPRC Pvt. Ltd.
MORPHO-PHYSIOLOGICAL ASPECTS OF MUNGBEAN (VIGNA RADIATA L.)
IN RESPONSE TO WATER STRESS
SHIHAB UDDIN1, SHAHNAJ PARVIN2 & M. A. AWAL3
1,2
Department of Agronomy, Bangladesh Agricultural University, Mymensigh, Bangladesh
3
Department of Crop Botany, Bangladesh Agricultural University, Mymensigh, Bangladesh
ABSTRACT
Water limitation may prove to be a critical constraint to crop growth. Mungbean is most susceptible in that
respects neither tolerate deficiency nor the excess moisture. Therefore, the present experiment was conducted to assess
water stress consequence on the morpho-physiological attributes of mungbean (Vigna radiata L.) cv. BINA mung 5 in
Agronomy Field Laboratory, Bangladesh Agricultural University, Bangladesh during October 2011 to February 2012. The
trial comprised seven treatments of irrigation in different growth stages. Results revealed that moisture stress hampered the
mungbean growth significantly and reduced the growth rate. All morphological and physiological attributes showed the
best performance under T7 where three irrigations applied and the lowest performance showed under T 1 (no irrigation) due
to moisture scarcity. Moisture scarcity resulted higher flower and pod abscission (53%) which enhanced early maturity of
mungbean.
The lowest values of assimilate partitioning were found from no irrigation might be the highest level of moisture
stress compare to other treatments which changed the distribution of photosynthetic pattern. Flowering to maturity found
the most critical stage where water scarcity reduced pod dry matter. Maintain adequate soil moisture during the period of
flowering to pod maturity encouraged pod filling and ensure higher yield of mungbean.
KEYWORDS: Water Stress, Mungbean, Irrigation, Growth Rate, Assimilate Partitioning, Moisture Sensitive Phase
INTRODUCTION
Pulses play a vital role to meet the protein demand of human diet. Pulses are considered as the poor people’s meat
as it is the cheapest source of protein. In Bangladesh, per capita daily consumption of pulses is only 13.29 g day-1 (BBS,
2011). While the World Health Organization (WHO) suggests consuming 45 g day -1 per capita pulses in Bangladesh . To
maintain the supply of this level, the Government of Bangladesh has to spend a huge amount of foreign currency each year.
Annual import of pulses in Bangladesh is approximately 108000 m tons (BBS, 2011). Mungbean is highly adapted to the
agro-climatic condition of Bangladesh.
Though the agro-ecological condition of Bangladesh is favourable for mungbean cultivation, its area under
cultivation and total production are low in this country. Soil moisture stress is an environmental condition which affects
physiological processes of the plant. Mungbean is cultivated during dry season (October to April) in Bangladesh and
during this period no rainfall causes depletion of soil moisture level resulting drought effect that impair the physiological
aspect of dry matter accumulation. A common feature of the climate in Bangladesh is the uncertainty of rainfall, therefore
probable significant soil water deficit leading to plant water deficit at various stages of growth.
Drought is a widespread climatic event which frequently limits growth of mungbean. Mungbean response to water
stress resulting in lower yields (Miah and Carangal, 2001). The decrease in crop biomass production is frequently observed
138
Shihab Uddin, Shahnaj Parvin & M. A. Awal
in response to water deficit. Drought problems for mungbeans are worsening with the rapid expansion of water stressed
areas of the world including 3 billion people by 2030 (Postel, 2000). Crop yield of mungbean is more dependent on an
adequate supply of water than on any other single environmental factor (Kramer and Boyer 1997). In winter cultivation
when temperature is low, relative humidity is low and evapotranspiration is greater, then 3-4 times irrigation may need to
obtain higher yields of mungbean to overcome drought effect (Lal et al., 2000). Moisture deficiency during flowering
causes abscission of flower bud and hampers pod development.
The response of grain legume to moisture stress is often related to so-called ‘moisture sensitive period’ -certain
developmental phases in which the plant is or appears by its observed response to be more sensitive to moisture conditions
than during other phases. Maqsood et al. (2000) observed that mungbean suffer due to water stress when grown in an
upland rice soil and that irrigation at vegetative and flowering plus pod development stages improve seed yield. Most
prominent aspect of growth and development of
mungbean is that the plant is sensitive to drought stresses, as a
consequence of which growth and developments go significantly below potential.
The evidence for the existence of moisture sensitive phases (when yield is decreased more by drought) in
munbean is weak especially when mungbean cultivated in rainfed condition. Mungbean cultivation has to undergo
significant drought period in dry region of Bangladesh which is the major constrain of growth and pod filling. Therefore,
the present experiment was undertaken to evaluate the effect of drought stress on the morho-physiological attributes of
mungean and to find out optimum stages of irrigation for increased growth of mungbean (cv. BINA mung 5) resulting
maximum yield.
MATERIALS AND METHODS
The experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University,
Mymensingh-2202, Bangladesh during October 2011 to Febraury 2012. The land was medium high, well drained siltyloam its general fertility level was low with pH 6.82 and low in organic matter content (1.19%). The selected variety of
mungbean in this experiment was BINA mung 5. There were seven treatments namely, T1 = No irrigation, T2 = One-stage
irrigation (Emergence-Flowering), T3 = One-stage irrigation (Flowering-Pod setting), T4 = One-stage irrigation (Pod
setting-Maturity), T5 = Two-stage irrigation (Emergence- Flowering-Pod setting), T6 = Two-stage irrigation (FloweringPod setting-Maturity), T7 = Three-stage irrigation (Emergence-Flowering-Pod setting-Maturity).
The experiment was laid out in a randomized complete block design with four replications. The whole
experimental area was divided into four blocks. Each block was divided into seven unit plots of 4.0m × 2.5m size. The
treatments were randomly allocated. Each unit plot was uniformly fertilized at the time of land preparation with urea, triple
superphosphate (TSP), muriate of potash (MOP), gypsum, zinc sulphate and molybdenum @ 40, 100, 60, 60, 4 and 1 kg
ha-1, respectively (BINA, 2008). The seeds were sown on 15 October 2011 in rows at 2-3 cm soil depth and row to row
distance was 30 cm. Seeds were sown @ 25 kg ha-1. Weeding and thinning were done at 20 and 40 days after sowing
(DAS).
Soil moisture level was determined by measuring field capacity. Before irrigation the field capacity was
determined and irrigation was applied up to saturation point. After 24 hours the excess water was drained out. Then soil
sample was collected by using auger at 15 cm depth. The collected sample was oven dried at 105º C for 16-24 hours or in
other words, until a constant weight is obtained. Oven dried soil was weighed and soil moisture content was calculated by
determining the loss in weight on drying and the weight of the oven dry soil from the following formula:
Morpho-Physiological Aspects of Mungbean (Vigna radiata L.) in Response to Water Stress
The percentage of moisture at field capacity =
139
W1  W 2
× 100 mass basis
W2  W
(Where, weight of empty dish with lid = W g, weight of dish with lid + weight of moist soil = W 1 g, weight of
dish with lid + weight of oven dry soil = W 2 g)
Table 1: Measurement of Field Capacity
Depth of Soil
Layer in (cm)
0-15
When Field
Capacity
Measured at DAS
0
10
20
30
40
50
60
70
80
90
Moisture Percentage on Oven Dry Basis
At Field
Acute when Irrigation
Capacity
was Applied
41.2
21.4
40.3
20.8
39.8
20.5
39.5
19.9
38.9
19.7
38.7
18.8
38.4
18.4
38.1
17.9
37.7
17.5
37.5
17.3
Table 2: Number of Irrigation and Amount of Water Applied
Treatments
Stage for Irrigation
T1
T2
T3
T4
T5
T6
T7
No irrigation
One-stage irrigation (E-F)
One-stage irrigation (F-P)
One-stage irrigation (P-M)
Two-stage irrigation (E-P)
Two-stage irrigation (F-M)
Three-stage irrigation (E-M)
Irrigation Strategy
Amount
Number
(mm)
180
6
70
2
75
2
220
8
140
4
260
10
To study ontogenic growth characteristics a total of five harvest was made, data were collected on some morhophysiological attributes. The first crop sampling was done at 30 DAS and continued at an interval of 15 days up to 90
DAS. From each plot, five plants were randomly selected and uprooted for obtaining data on necessary parameters. Plant
height was taken to the length between base of the plant and the tip of the main stem and was expressed in cm.
Number of branches and leaves plant-1 were counted separately from selected plants and then the average number
of them were computed. The plants were separated into roots, stem and leaves and the corresponding dry weights were
recorded after oven dry at 80±2°C for 72 hours.
The leaf areas of each sample were measured by LICOR automatic leaf area meter (model: LI 3000, USA). Leaf
area index and the growth analysis like absolute growth rate, relative growth rate and net assimilation rate were carried out
following the formula of Hunt (1978).
Crop Growth Rate (CGR)
Crop growth rate is the increase in the plant dry matter production per unit of time per unit of ground area (Hunt,
1978). It was calculated by using the following formula:
140
Shihab Uddin, Shahnaj Parvin & M. A. Awal
CGR =
W 2  W1
g m-2 day-1
T2  T1
Where, W1 and W2 are the total dry weight at the time T1 and T2, respectively.
Relative Growth Rate (RGR)
Rate of DM production per unit of time i.e. RGR =
ln W2  ln W1
g g-1 day-1
T2  T1
Where, W2 and W1 are the DM at the time T2 and T1, respectively.
Net Assimilation Rate (NAR) or Unit Leaf Rate (ULR) or E
Rate of DM production per unit of leaf area per unit of time i.e.
NAR =
W 2  W1
ln LA2  ln LA1
×
g m-2 day-1
T2  T1
LA2  LA1
Where, W2 and W1 are the DM at the time T2 and T1 respectively. LA2 and LA1 are leaf area at the time T2 and T1,
respectively.
Leaf Area Ratio (LAR)
LAR expresses the ratio between the area of leaf lamina or photosynthesizing tissue (LA) and the total respiring
plant tissues or total plant biomass (W). It can be expressed by the following formula: LAR =
LA 2 -1
cm g
W
Leaf Area Index (LAI)
The Ratio of total surface area of leaves of a unit area to unit land area
LAI =
LA
, Where, LA is the leaf area (cm2) and G is the ground area (cm2).
G
The total dry matter was calculated from the summation of dry weight of leaf, stem, root and pod per plant. The
recorded data on various plant characters were statistically analyzed through analysis of variance (ANOVA). The
differences among treatment means were compared by Duncan’s Multiple Range Test (Gomez and Gomez, 1984) with the
help of a computer based statistical package programme MSTAT-C.
RESULTS AND DISCUSSIONS
Morphological Characters
The effect of irrigation on plant height was significant at 60 DAS, 75 DAS and 90 DAS (Figure 1). At 60 DAS
highest plant height (36.51cm) was obtained from T6 where two irrigations were applied at flowering to pod dry matter and
maturity and the lowest (30.08 cm) was obtained from T 1. Similar results were found at 75 and 90 DAS.
These results indicate that plant height increased with the increase of number of irrigation and decreased in no
irrigation condition might be due to inhibition of cell division or cell enlargement for soil moisture stress. Similar result
was also reported by Ranawake et al. (2011) who reported that significant reduction in length between stressed and watered
plant .
Morpho-Physiological Aspects of Mungbean (Vigna radiata L.) in Response to Water Stress
141
Figure 1: Effect of Water Stress on the Plant Height of Mungbean
Figure 2: Effect of Water Stress on the Number of
Branch Mungbean
Figure 3: Effect of Water Stress on Number of Leaves
of Leaves of Mungbean
The effect of irrigation on the number of branches plant -1 and number of leaves plant-1 was significant at 30 DAS,
60 DAS and 90 DAS and 30 DAS, 75 DAS and 90 DAS, respectively (Figure 2 & 3). The highest number of branches
plant-1 was found in T4 where one irrigation was at pod setting to maturity (P-M) and the lowest was observed in T1 with
no irrigation condition. Furthermore, the highest number of leaves per plant was also found in T4 where one irrigation was
applied at P-M and the lowest was found in T1 where no irrigation was applied. The result showed that as the water stress
increased the number of branches and leaves plant -1 decreased, this indicated that water stress had direct effect on initiation
of branch and leaves. Ranawake et al. (2011) found that water stress affect the crop phenology, leaf area development and
number of leaves of mungbean.
Maturity, Abscission and Senescence
Maturity, abscission and senescence are common phenomena in the ontogeny of a plant. Abscission is the natural
separation of leaves, buds, flowers, fruits etc. from the stems or other plant parts. The process of deterioration that
142
Shihab Uddin, Shahnaj Parvin & M. A. Awal
accompanies ageing and death of an organ or organism is called senescence. Days required from germination to various
phase of maturity, abscission and senescence were found significant among the treatments (Table 3).
The highest number of days required to initiate flowering, leaf senescence and pod maturity were found 46.15,
83.25 and 93.55 days, respectively in T7 and the lowest duration required to initiate flowering, leaf senescence and pod
maturity were found at 38.65 days, 73.85 days and 85.83 days, respectively in T1. These results indicate that moisture
stress causes early flowering, pod formation and maturity of plant. These percentages of flowering and pod abscission were
found different in different irrigation treatment (Table 3). About 53 percent flower and pod abscised in no irrigation
condition. The irrigated plant showed lower percentage of flower and pod abscission. In three irrigated (T 7) plants lowest
abscised percentage were recorded. These results indicate that percentage of flower and pod abscission increased with
increasing moisture stress which was supported by (Hossain et al. 2010).
Table 3: Days to Flowering and Maturity and Percentage Flower Plus Pod Abscission in Mungbean
under Different Irrigation Strategy
Irrigation
Strategy
T1
T2
T3
T4
T5
T6
T7
CV (%)
Sx
Sig. Level
First
Flowering
38.65f
39.90e
42.53d
43.88c
44.68b
45.28b
46.15a
1.23%
2.69
**
Days from Sowing to
First Sign of
First Sign of
Leaf Senescence
Pod Maturity
73.85f
85.83e
e
76.35
86.78d
d
78.48
88.48c
c
79.48
90.18b
c
80.15
90.98b
b
81.48
91.93b
a
83.25
93.55a
0.69%
0.64%
3.02
2.82
**
**
% (Flower
+ Pod)
Abscission
53.88a
51.45b
48.08c
43.60d
40.95e
38.28f
36.03g
2.35%
6.42
**
Growth Attributes
Crop growth rate (CGR) varied significantly in different treatments (Figure 4). Overall CGR was recorded in T7
where three irrigations were applied but the lowest CGR was found in T1 where no irrigation was applied. These results
should that as the increased in crop age CGR increased and these results also supported by Sangakara (2004). He found
that crop growth rate reduced significantly with increasing soil moisture stress.
De Costa and Sanmugathasan (2002) reported that crop growth rate (CGR) increased significantly with the
number of stages irrigated with irrigation during the flowering stage having the highest positive effect. Mean CGR during
the main pod filling period exceed the corresponding overall CGR in all treatments indicating re-translocation of
assimilates from vegetative organs.
Relative growth rate varied significantly under different treatment at 30-45 DAS (Figure 5). At 30-45 DAS, the
highest relative growth rate (163.13 mg g-1 day plant-1) was found from T7 which was statistically similar with T5 and T6.
These result showed that RGR decreased with increasing crop age and was found the highest from T7 in all growth stages.
Net assimilation rate (NAR) influenced significantly by irrigation (Figure 6). The highest NAR (32.34 mg cm -2 day-1 plant1
) was recorded from T7 followed by T5, T6 and the lowest (8.94 mg cm-2 day-1 plant-1) NAR from T1.
The result indicated that NAR decreased with increasing crop age and found the highest as the number of stages
irrigation increased. The decreasing trend of NAR might be reduced photosynthate during the later stages because of
senescence of leaves.
Morpho-Physiological Aspects of Mungbean (Vigna radiata L.) in Response to Water Stress
143
These results also supported by Moradi et al. (2008) where they found that water stress at vegetative growth stage
significantly decreased NAR and concluded that to maximize mungbean NAR, irrigation should be extended across all
growth stages, especially during the reproductive phase.
Figure 4: Effect of Water Stress on Crop Growth Rate
of Mungbean
Figure 6: Effect of Water Stress on Net Assimilation
Rate of Mungbean
Figure 5: Effect of Water Stress on Relative Growth
Rate of Mungbean
Figure 7: Effect of Water Stress on Leaf Area
Ratio of Mungbean
Leaf area ratio (LAR) was influenced significantly by irrigation application (Figure 7). The highest LAR was
found from T1 and the lowest from T7. The effect of irrigation on LAI was also significant from 60 DAS to 90 DAS in
different treatments (Figure 8). The highest LAI (0.054) was found from T 7 which was statistically similar with T5 and T6,
respectively. The lowest LAI (0.32) was observed from T 1 which was statistically similar with T2 and T4. These result
showed that LAI increased with increasing age and attaining a peak at 60 and 75 DAS and thereafter decreased. These may
be due to leaf senescence at maturity. Less assimilate production for inhibition of photosynthesis and lower cell division of
144
Shihab Uddin, Shahnaj Parvin & M. A. Awal
plate meristimatic tissue of leaves might be the causes of lower leaf area production under soil moisture stress condition.
LAI decreased with increasing soil moisture deficits (De Costa and Shanmugathasan, 2002).
Figure 8: Effect of Water Stress on Leaf Area Index (LAI) of Mungbean
Assimilate Partitioning
Growth is irreversible increase in size, volume and dry matter. Increase in dry matter, however, is the most
reliable parameter to assess growth. In present investigation, the total dry matter and their partitioning in roots, stems,
leaves, shoots and pods were studied. Irrigation had significant effect on root dry weight (Table 4). At 30 DAS the highest
root dry weight (0.89g) was found from T 5 which was statistically similar from irrigation treatment T4, T6, T7, respectively
and the lowest root dry weight (0.23g) from no irrigation condition (T 1). At 45 DAS, 60 DAS and 75 DAS the highest root
dry weight was observed from three-stage irrigation condition (T7) but at 90 DAS T6 gave highest value than T7 and the
lowest root dry matter from T1. The results indicated that water stress decreased the root dry weight. These results also
supported by Singh et al. (2003). He reported that increase in moisture level from 0.3 to 0.9 (ID/CPE) significantly
increased their root dry weight. Dhole and Reddy (2010) found that the numbers of roots per plant decrease with decrease
in water potential.
Table 4: Effect of Irrigation on Root Dry Weight (g) of Mungbean
Irrigation Strategy
T1 = No irrigation
T2 = One-stage irrigation (E-F)
T3 = One-stage irrigation (F-P)
T4 = One-stage irrigation (P-M)
T5 = Two-stage irrigation (E-P)
T6 = Two-stage irrigation (F-M)
T7 = Three-stage irrigation (E-M)
CV (%)
Sx
Significance Level
30 DAS
0.23c
0.53b
0.64ab
0.86a
0.89a
0.73ab
0.83a
13.03
0.26
**
Root Dry Weight (g)
45 DAS
60 DAS
75 DAS
0.70f
1.11f
1.56f
e
e
1.59
1.81
2.98e
d
d
1.60
2.74
3.88d
c
c
2.26
3.28
4.87c
ab
b
2.88
4.37
5.68b
2.80bc
4.90a
7.10a
a
a
3.45
5.07
7.30a
18.85
8.6
8.04
0.96
1.48
2.03
**
**
**
90 DAS
2.81e
3.44e
4.28d
5.70c
6.70b
8.09a
7.41ab
10.36
1.98
**
Similarly stem dry weight plant-1 (g) also varied among different treatment (Table 5). At 30 DAS the highest stem
dry weight (1.75g) was found from irrigation treatment T 5 which was statistically similar from irrigation treatment T3, T4,
145
Morpho-Physiological Aspects of Mungbean (Vigna radiata L.) in Response to Water Stress
T6 and T7, respectively and the lowest stem dry weight (0.5g) from no irrigation condition (T 1). In rest of the cases, the
highest stem dry weigh was observed from three-stage irrigation condition (T7) due to sufficient availability of soil
moisture and the lowest stem dry weight from T1. The results showed that water stress reduced stem dry weight. This
indicated that after irrigation photosynthesis was increased and more dry matter was produced and that dry matter was
stored in stem. Stem is the mechanical support for plant to stand still. The results of the present study is similar to the
findings of Ranawake et al. (2011) who reported progressively reduced stem dry matter with progressive increase on
moisture stress in mungbean. Similar results were also found by Patel et al. (2003) in different crops.
Table 5: Effect of Irrigation on Stem Dry Weight Plant-1 and Leaf Dry Weight Plant-1 of Mungbean
Irrigation
Strategy
T1
T2
T3
T4
T5
Stem Dry Weight Plant-1 (g)
Leaf Dry Weight Plant-1 (g)
30 DAS
45 DAS
60 DAS
75 DAS
90 DAS
30 DAS
45 DAS
60 DAS
75 DAS
90 DAS
0.50c
1.05b
1.26ab
1.64a
1.75a
1.33d
2.59c
3.11bc
3.59b
4.97a
2.09d
3.88c
5.08b
5.77b
7.54a
2.50f
4.66e
6.47d
7.96c
9.74b
4.66f
5.87f
8.11e
10.33d
11.68c
0.97c
1.55b
1.76ab
2.14a
2.25a
1.83d
3.09c
3.61bc
4.09b
5.47a
2.59d
4.38c
5.58b
6.27b
8.04a
3.00f
5.23e
6.97d
8.46c
10.24b
5.16g
6.37f
8.61e
10.83d
12.18c
T6
1.46ab
4.75a
7.68a
11.92a
13.10b
1.96ab
5.25a
8.18a
11.12ab
13.60b
T7
CV (%)
Sx
Sig. Level
1.46ab
16.88
0.50
**
5.11a
13.9
1.39
**
7.84a
9.21
2.12
**
12.37a
5.87
3.49
**
14.72a
8.36
3.60
**
1.96ab
19.65
0.51
**
5.61a
12.22
1.39
**
8.34a
8.47
2.12
**
11.71a
8.03
3.09
**
15.55a
6.41
3.64
**
Table 6: Effect of Irrigation on Shoot Dry Weight and Root/Shoot Ratio of Mungbean
Irrigation
Strategy
T1
T2
T3
T4
T5
T6
T7
CV (%)
Sx
Sig. Level
Shoot Dry Weight Plant-1 (g)
Root/Shoot Ratio
30 DAS
45 DAS
60 DAS
75 DAS
90 DAS
30 DAS
45 DAS
60 DAS
75 DAS
90 DAS
1.43c
2.60b
3.02ab
3.79a
4.01a
3.42ab
3.43ab
22.76
1.02
**
3.16d
5.67c
6.72bc
7.69b
10.43a
10.01a
10.72a
13.01
2.78
**
4.68d
8.25c
10.65b
12.03b
15.59a
15.86a
16.19a
8.84
4.23
**
5.50f
9.97e
13.44d
16.42c
19.98b
21.73ab
22.92a
8.3
6.18
**
9.82g
12.24f
16.72e
21.16d
23.86c
26.71b
30.60a
6.57
7.29
**
0.14b
0.21a
0.21a
0.22a
0.22a
0.22a
0.24a
11.05
0.03
**
0.22c
0.28ab
0.24bc
0.29a
0.28ab
0.28ab
0.32a
12.36
0.04
**
0.24cd
0.22d
0.26bc
0.27bc
0.28ab
0.31a
0.31a
8.48
0.04
**
0.28b
0.30ab
0.29ab
0.30ab
0.28b
0.33a
0.32ab
6.4
0.02
NS
0.29bc
0.28bc
0.26c
0.27bc
0.28bc
0.30ab
0.33a
8.06
0.03
**
The highest leaf dry weight was observed from three-stage irrigation condition (T7) which was statistically similar
with T5 and T6, respectively and the lowest leaf dry from no irrigation condition (Table 5). The results revealed that as the
number of stages of irrigation increased leaf dry weight was increased. Water stress might decrease translocation of
assimilates to the leaf, which lowered the amount of leaf dry weight under stress condition Gupta et al. (2005). In case of
shoot dry weight at 30 DAS the highest shoot dry weight plant -1 (4.01g) was found from irrigation treatment T 5 which was
statistically similar from irrigation treatment T3, T4, T6 and T7, respectively and the lowest shoot dry weight (1.43g) from
no irrigation condition (T1). With increasing in age, the highest shoot dry weight (10.72g) was observed from three-stage
irrigation condition (T7) which was statistically similar with T5 and T6, respectively and the lowest shoot dry weight
(3.16g) from no irrigation condition. The results indicated that like before the moisture scarcity hampered shoot dry weight
in mungbean. These results also supported by Singh et al. (2003). He reported that increase in moisture level from 0.3 to
0.9 (ID/CPE) significantly increased their shoot dry weight. Irrigation treatment influenced the root /shoot ratio
significantly (Table 6). In all cases, the highest root/shoot ratio (0.24) was found from T 7 which was statistically similar
146
Shihab Uddin, Shahnaj Parvin & M. A. Awal
from irrigation treatment T2, T3, T4, T5 and T6, respectively and the lowest (0.14) from no irrigation condition (T 1). The
results indicated that water deficiency resulting in lowered root shoot ratio.
The pod dry weight plant-1 significantly influenced by different irrigation treatment (Figure 9). With the increase
of age of pod, the highest pod dry weight was found from three irrigations which was statistically similar with T 6 and the
lowest pod dry weight from no irrigation condition. These result showed that as the irrigation frequency increased, the pod
dry weight plant-1 increased. The result was also supported by De Costa and Shanmugathasan (2002). They found that the
highest pod dry matter indicated the highest re-translocation of assimilate and it was observed in the treatment which
irrigated in all the growth stages. Pod dry weight of mungbean gradually increased with increasing irrigation.
The development of reproductive organs, which is under the control of photo-assimilate production and
partitioning by the source tissues, is at this stage the most critical (Taiz and Zeiger, 2002). Therefore, increased drought at
this stage has a pronounced effect on fruit development and yield. Similar results also reported by Moradi et al. (2008) and
found that reproductive phase was more sensitive to water deficit. The early stage of pod development was characterized
by active cell division in the young ovules and rapid pod expansion. The yield loss caused by drought stress was mainly
due to an increased rate of floral and pod abortion (Liu et al. 2003).
Figure 9: Effect of Water Stress on Pod Dry
Matter of Mungbean
Figure 10: Effect of Water Stress on Total
Dry Matter Mungbean
Dry matter accumulation after flowering greatly influenced seed yield. Most of the photosynthates produced at
this stage is used for pod and seed development. The effect of irrigation on the total dry matter plant -1 was statistically
significant (Figure 10). The highest total dry matter was found from T 7 in all growth stages and the lowest from T1 no
irrigation condition. Therefore, it is found that three irrigation about produced 50% more biomass than no irrigated plots.
The results showed that dry matter accumulation increased with the increase of irrigation frequency.
This indicated irrigated had direct effect on TDM. DM production of mungbean decreased with increasing soil
moisture deficits. De Costa and Shanmugathasan (2002) reported that maximum total biomass increased significantly with
the number of stages irrigated, with irrigation during the vegetative stages having the highest positive effect and found that
drought stress significantly decreased the total dry matter production.
Morpho-Physiological Aspects of Mungbean (Vigna radiata L.) in Response to Water Stress
147
CONCLUSIONS
Water scarcity drastically shortened all morphological, physiological and assimilate partitioning pattern of
mungbean. Pod dry matter is the most important indicator of achieving the better seed yield. In that case it was observed
that no irrigation caused the less dry matter and finally before harvesting two stages irrigation at flowering to maturity
resulted the higher pod dry weight than the three stage irrigation from emergence to maturity. Therefore it can be
concluded that to overcome the drought effect and obtaining the higher yield, the crop field should be irrigated during the
period flowering to maturity which is indication of most moisture sensitive phase during the life cycle of mungbean cv.
BINA mung 5. This work enabled us to further understand the physiological aspect to water stress in this legume and after
water stress treatments seem reliable metabolic response to evaluate drought tolerant mungbean cultivars.
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