NUTRITIONAL EVALUATION OF THE GRAINS AND LEAF NITRATE REDUCTASE ACTIVITY IN PIGEONPEA GENOTYPES
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Date
2002
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Mahatma Phule Krishi Vidyapeeth, Rahuri.
Abstract
The present investigation aims at evaluating the
proximate composition of grains of seventeen pigeonpea (Cajanus
cajan L.) genotypes. In addition, the nitrate reductase (NR) activity
from the trifohate leaves of pigeonpea plants was standardized by an
in vivo method. The nitrate reductase activity in the leaves of
seventeen pigeonpea genotypes was also examined and correlated
with gram 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 soil-filled pots under
natural daylight conditions during the months from June to August
2001.
Grains of seventeen pigeonpea genotypes were analysed
for biochemical parameters viz., moisture, ash, crude protein, crude
fat, crude fibre, total carbohydrates and limiting amino acids such as
methionine and tryptophan. The grains of all the cultivars differed
significantly in their contents of moisture (7.82 to 12.38 %), ash (2.89
to 5.96 %), crude protein (16.93 to 26.92 %), crude fat (1.67 to 2.91 %),
crude fibre (5.84 to 11.23 %), carbohydrates (51.84 to 60.79), methionine (0.80 to 1.16 g 16 g-1 N) and tryptophan (0.68 to 1.09 g 16
g-1 N).
The infiltration media (5.0 ml) used for the determination
of in vivo NR activity for plus 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 was
observed in NR activity in the trifoliate leaves of pigeonpea. The
average NR activity was low at 8.00 a.m. in the morningl^ncreased
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 potentials of NR from different leaves of 21-day-old plants indicated that the
highest NR activity was observed in the cultivar ICPL-87, while the
lowest was observed in ICPL-87119. The cotyledonary leaves had the
highest NRA in all the cultivars investigated. The significant positive
correlation between NR activity in different leaves and protein
content in the grains of the pigeonpea genotypes indicated that the
genotypes with higher protein content and NR activity such as
ICPL-87 and PT-11-39 can be selected for further varietal
improvement programmes. The highest NR activity was largely
confined to petioles in 45-day-old pigeonpea plants indicating that
petioles are the major site of nitrate reduction and assimilation in
pigeonpea, which was followed by leaves and stems. The roots and
root nodules, however, had much lower level of NR.
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