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Genomics and Applied Biology
16
makeup, the major physiological constraints limiting
its production are flower drop and fruit drop (Ojeaga
and Ojehomon, 1972). This performance of the crops
can be overcome by foliar application of growth
regulating chemicals at the crucial stages of the crop,
which is one of the latest trends in agriculture. The
growth regulating chemicals bioregulators can
improve the LAI, SLW and SLA and play a significant
role in improving the productive potential of the crop.
With this above background, the present investigation
was carried out.
1 Result
1.1 Crop growth rate (CGR) (g
·
m
-2
·
day
-1
)
Crop Growth Rate recorded between vegetative to
flowering stage (30~45 DAS) flowering to pod filling
stage (45~60 DAS) and pod filling to harvest stage
(60~75 DAS) is presented in (Table 1). The crop
growth rate ranged from 0.54 to 0.78, 1.22 to 1.84 and
1.02 to 1.36 g
·
m
-2
·
day
-1
at 30~45, 45~60 and 60~75
DAS, respectively. The treatment T
7
(N 25 kg/ha +
Urea 2% + BR 0.1 ppm) recorded the maximum CGR
(0.78, 1.84 and 1.36 g
·
m
-2
·
day
-1
) at all the stages of
growth. There was no significant variation among the
treatments at pod filling to harvest stage.
1.2 Net assimilation rate (NAR) (mg
·
cm
-2
·
day
-1
)
The trend of NAR decreased from 30~45 DAS of crop
growth to 60~75 DAS (Table 2). However, the
declining trend was reduced by the application of
nutrients and growth regulators. The NAR at various
stages of crop growth viz., 30~45 DAS, 45~60 DAS
and 60~75 DAS stages ranged from 0.54 mg
·
cm
-2
·
day
-1
to
0.66 mg
·
cm
-2
·
day
-1
, 0.50 mg
·
cm
-2
·
day
-1
to 0.65 mg
·
cm
-2
·
day
-1
and 0.50 mg
·
cm
-2
·
day
-1
to 0.63 mg
·
cm
-2
·
day
-1
respectively. The treatment T
7
(N 25 kg/ha + Urea 2%
+ BR 0.1 ppm) recorded the highest NAR values at all
the stages of crop growth, followed by T
3
and T
4
treatments.
Table 1 Effect of nitrogen nutrition and growth regulators on crop growth rate (g·m
-2
·day
-1
) in black gram at different growth stages
Treatment
30~45 DAS
45~60 DAS
60~75 DAS
T
1
0.54
1.22
1.02
T
2
0.56
1.28
1.07
T
3
0.71
1.62
1.20
T
4
0.60
1.53
1.21
T
5
0.61
1.44
1.03
T
6
0.55
1.51
1.09
T
7
0.78
1.84
1.36
T
8
0.59
1.42
1.01
T
9
0.60
1.58
1.04
Mean
0.61
1.49
1.11
SEd
0.02
0.06
0.04
CD (P=0.05)
0.05
0.13
0.98
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
1.3 Nitrate reductase activity (µg NO
2
·
g
-1
·
hr
-1
)
The trend of NRase activity estimated at four stages of
growth is presented in Table 3. Higher NRase activity
was observed at the pod filling stage (60 DAS) for all
the treatments including control. At the same stage,
significant increase (56.2 µg NO
2
·
g
-1
·
hr
-1
) was
observed with N 25 kg/ha + urea 2% + 0.1 ppm BR
(T
7
) treated plants compared to other treatments. The
enzyme activity recorded for treatment T
4
was found
to be statistically comparable with the values of
treatment T
7
.
1.4 Indole acetic acid oxidase activity (IAAO) (µg
of unoxidised auxin
·
g
-1
·
hr
-1
)
The data on IAA oxidase estimated at specific stages
and expressed in terms of unoxidized auxin content is
Genomics and Applied Biology