NUTRITIONAL EVALUATION OF GRAINS AND LEAF NITRATE REDUCTASE POTENTIAL OF SOME PIGEONPEA GENOTYPES
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Date
2003
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MPKV, UNIVERSITY LIBRARY RAHURI
Abstract
The present investigation involves the nutritional evaluation
of grains of different maturity group pigeonpea [Cajanus cajan (L.)
Millsp.] genotypes. In addition, nitrate reductase (NR) assay from the
trifoliate leaves of pigeonpea plants was standardized by an in vivo
method. The nitrate reductase enzymatic potential in the leaves of fourteen
pigeonpea genotypes was also examined and correlated with grain protein
contents. Further, it was desired to know the distribution of NR activity in
different plant parts such as leaves, stems, petioles, roots and root nodules
in 45-day-old pigeonpea plants. The pigeonpea plants were grown in soilfilled
earthen pots under natural daylight conditions during the months
from August to October, 2002.
The grains of fourteen pigeonpea genotypes were analysed for
various biochemical constituents,such as ash, crude protein, crude fat,
crude fibre, total carbohydrates and limiting amino acids such as
methionine and tryptophan. The grains of all the genotypes differed
significantly in their contents of moisture (7.21 to 10.17%), ash (3.19 to
5.67%), crude protein (17.59 to 26.91 %), crude fat (1.86 to 2.83%), crude
fibre (4.17 to 6.66%), total carbohydrates (51.11 to 61.02%), methionine
(0.80 to 1.22 g 16 g"1 N) and tryptophan (0.60 to 1.09 g 16 g"1 N).
The infiltration media (5.0 ml) used for the determination of
in vivo NR activity for + KNO3 assays in pigeonpea trifoliate leaves were
standardized in respect of nitrate (100 mM), n-propanol, (1%, v/v) and
Triton-X-100 (0.05%,v/v). The diurnal variability in NR activity of
trifoliate leaves was also observed. The average NR activity was low at
6.00 a.m. in the morning which increased rapidly as the day advanced,
until it reached a maximum level at 2.00 p.m. The NR activity, however,
declined during the afternoon hours, reaching to a minimal level at 6.00
p.m. The enzymatic potential of NR from different leaves of 21-day-old
plants indicated that the highest NR activity was observed in the genotype,
ICPL-87, while the lowest in PT-1037. The cotyledonary leaves had the
highest NR activity in all the genotypes investigated. The significant
positive correlation between NR activity indifferent leaves and protein
content in the grains of the pigeonpea genotypes indicated that the
genotypes wit h higher protein conten t and NR activity such as ICPL-87,
MDRL-14 and MDRL-6 can be selected for furthe r varietal improvemen t
programmes. The highest NR activity was largely confined to petioles in
45-day-old pigeonpea plants indicating petioles as the major sit e of nitrate
reduction and assimilation, whic h was followe d b y leaves and stems. The
roots and root nodules, however, had much lowe r NR level.
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