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Plant Gene and Trait, 2013, Vol.4, No.5, 25
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4 Discussions
4.1 Photosynthetic pigments
The increase in chlorophyll content reflects increased
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photochemistry, photosynthates production and
dry matter accumulation. The result of the present
study indicated that the fractions of chlorophyll, a and
b also total chlorophyll increased up to pod filling
stage and declined at the time of harvest. Chlorophyll
accumulation in leaves was double time higher between
flowering and pod filling stages, as compared to
vegetative stage, whereas, for chlorophyll b, the
maximum accumulation was noticed at vegetative
stage itself. The total chlorophyll content, however,
reflected the trend of chlorophyll a content. At the
time of harvest, chlorophyll a and total content showed
about 30 per cent reduction, whereas chlorophyll b
showed only 10 per cent reduction. This decline was
related to the activation of chlorophyllase enzyme, as
the result, the water soluble porphyrin fragments were
exported from chloroplast to vacuole, thus there was a
loss in leaf greenness (Matile et al., 1982). The nutrients
and plant growth regulators played a productive role
in upregulating the enzymes involved in chlorophyll
synthesis. The treatmental combination N (25 kg/ha) +
BR (0.1 ppm) + Urea (2%) caused a remarkable increase
in a, b and total content of the leaves at all the stages
of the growth, as observed in the present study. This
finding was strongly supported by the results of
Prabakaran (2002) in black gram. Mitra and Ghildyal
(1987) opined that the supply of nitrogen through
foliage is essential during pod developmental stage for
the maintenance of high rate current photosynthesis.
Kulaeva et al., (1991), however, specified the role of
BR in inducing chlorophyll synthesis, through the
activation of enzyme proteins. In mung bean, the
enhancement in chlorophyll content by BR treatment
had been attributed to several factors including
inhibition of senescence and enhanced uptake of iron
(Bhatia and Jatinder kaur, 1997). Similarly in wheat
high photosynthetic rate induced by BR application
was directly related to enhanced chlorophyll content
of the leaf (Sairam, 1994). In addition to the
combination with BR 0.1 ppm, CCC 200 ppm along
with Urea 2 per cent also revealed its significant effect
in enhancing the chlorophyll content of the present
study. Ameregouda et al. (1994) supported this
finding with the result that in wheat, foliar spray of
CCC was found highly effective in increasing the
chlorophyll content of the leaf. Similar finding made
by Sumathi (2005) in pigeon pea was also in close
confirmity with the results of the present study.
4.2 Soluble protein
The soluble protein content of the leaf, being a
measure of RuBP carboxylase activity was considered
as an index for photosynthetic efficiency. These were
reports that RuBP-case enzyme forms nearly 50 per
cent of the soluble proteins in leaves of many plants
(Joseph et al., 1981). Diethelm and Shibles (1989)
opined that the RUBISCO content per unit leaf area
was positively correlated with that of souble protein
content of the leaf. Vidyavardhini and Seeta Rama Rao
(1997) reported that foliar application of brassinolide
and 24-epibrassinolide at 0.5 ppm~3.0 ppm remarkably
increased the soluble protein content of the leaves in
groundnut. This finding strongly supported the results
of the present study, which indicated that the treatm-
ental combination N (25 kg/ha) + BR (0.1 ppm) + Urea
(2%) enhanced the soluble protein content by more
than 25 per cent at the time of flowering over control.
This effect of BR was explained by Gregory (1981)
that increased level of soluble protein content in the
brassinolide treated plants might be due to induction
of specific metabolic changes and increased protein
synthesis in cells. Kalinich et al. (1985) reported a
significant increase in RNA and DNA polymerase
activity and the synthesis of RNA, DNA and protein
in brassinosteroid treated bean and mungbean, which
might be the reason for increase in soluble protein
content in these crops. The other treatmental combin-
ation with CCC 200 ppm, of the present study also
showed its effectiveness in enhancing soluble protein
content, particularly, at the flowering stage of the
crop. In supporting this finding, Krishchenko et al.
(1983) reported that soluble protein content in wheat
increased remarkably during tillering and flowering