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Genomics and Applied Biology
18
Table 4 Effect of nitrogen nutrition and growth regulators on IAA-oxidase in black gram at different growth stages (µg unoxidised
auxin·g
-1
·hr
-1
)
Treatments
30 DAS
45 DAS
60 DAS
Harvest stage
T
1
88.1
121.4
147.2
116.0
T
2
71.3
118.7
128.6
78.4
T
3
69.0
109.1
114.9
89.3
T
4
68.7
101.5
109.4
78.6
T
5
73.8
116.9
124.3
84.2
T
6
80.7
111.0
120.4
92.5
T
7
65.8
98.5
105.6
74.8
T
8
78.4
105.2
117.6
86.4
T
9
85.6
120.7
138.5
109.5
Mean
75.54
111.22
122.67
89.75
SEd
3.33
4.83
5.42
4.05
CD (0.05)
7.07
10.24
11.50
8.58
Note: T
1
: Control; T
2
: N 25 kg/ha + Urea 2% + NAA 40 ppm; T
3
: N 50 kg/ha + CCC 200 ppm; T
4
: N 25 kg/ha + Urea 2% + CCC 200
ppm; T
5
: N 25 kg/ha + Urea 2% + Humic acid 0.1%; T
6
: N 25 k/ha + Urea 2% + Salicylic acid 100 ppm; T
7
: N 25 kg/ha + Urea
2% + Brassinosteriod 0.1 ppm; T
8
: N 25 kg/ha + Urea 2% + ZnSO4 0.5% + FeSO4 0.5% + Borax 0.2%; T
9
: N 25 kg/ha +
Water spray
2 Discussion
Crop production is determined by crop growth rate as
a function of light interception by the leaf area of a
crop (Whigham, 1983). Shibles and Weber (1966) also
stated that as CGR is a linear function of intercepted
irradiance, maintaining higher LAI has a positive
effect for higher dry matter production due to
increased CGR. As observed in the present study,
CGR of black gram exhibited an increasing trend from
vegetative to pod filling stage followed by a decline
thereafter. Since CGR is the product of NAR and LAI,
this trend indicated that in black gram CGR is closely
related to LAI rather than NAR. In supporting this
finding, Shibles and Weber (1966) observed a strong
positive correlation between CGR and LAI in soybean.
Plant growth hormones played a significant role on
GRR as observed in the present study. BR 0.1 ppm +
Urea 2% spray in addition to recommended dose of N
(25 kg/ha) strongly influenced CGR with more than
50 per cent increase over control, particularly between
flowering and pod formation stages. This finding is in
close confirmity with the results of Prakash et al.
(2007) in sesamum. Umadevi (1998) also quoted the
significant effect of BR in improving CGR in
sesamum. Cycocel (200 ppm) spray in addition to N
(50 kg/ha) also showed remarkable enhancement in
CGR with about 30% increase over control in black
gram of the present study. This finding was
corroborated with the result of Vijayakumar and
Abdulkhadar (1997) in cassava. This enhancement in
CGR was due to fast development of the sources as
well as sink.
The net assimilation rate is a measure of net
photosynthesis of leaves in crop community. In the
present investigation, net assimilation rate slightly
declined from vegetative to final stage of the crop.
Watson (1958) suggested that the cause for the
decrease in NAR with increased leaf area in crop
plants was due to mutual shading of the leaves, which
would decrease the leaf photosynthesis. Briggs et al.
(1920), however, viewed that the decreased NAR with
age was due to losses in respiration in all parts of the
plants. NAR was significantly influenced by hormonal
manipulation, particularly brassinolide. BR (0.1 ppm)
along with Urea (2%) increased the assimilation rate
by 22% during vegetative to flowering stage and 30%
during flowering to pod filling stages over control.
Similarly, N (50 kg/ha) + CCC (200 ppm) spray
resulted in 20% and 28% improvement in NAR over
control in these two stages respectively. These
findings were in confirmity with the results of Kalita
et al. (1994). Nemchenko et al. (1981) demonstrated
the positive rate of CCC in increasing net assimilation
rate of potato. Baghal and Yadhav (1992) explained
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