EVALUATIO N O F PROXIMAT E COMPOSITIO N O F GRAIN S AN D LEA F NITRAT E REDUCTAS E ACTIVIT Y I N DIFFEREN T MATURIT Y GROU P PIGEONPE A CULTIVARS
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Date
2004
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MPKV, UNIVERSITY LIBRARY RAHURI
Abstract
The present investigation aims at evaluating the proximate
composition of grains of seventeen pigeonpea (Cajanus cajan L.)
genotypes representing three maturity groups. In addition, an enzyme NR
was characterized from the trifoliate leaves of pigeonpea by an in vivo
method. The nitrate reductase activity in the leaves of pigeonpea was also
examined and correlated with grain protein contents. Diurnal variation in
NR activity and the distribution of enzyme activity in different plant parts
was also determined. The pigeonpea plants were grown in soil-filled pots
under natural day-light during the months from August to October, 2003.
The grains of different maturity group pigeonpea genotypes
were analysed for biochemical parameters, such as moisture, ash, crude
protein, crude fat, crude fibre, total carbohydrates and limiting aminoacids,
methionine and tryptophan. The grains of all the genotypes differed
significantly in their contents of moisture (8.32 to 12.11 %), ash (2.83 to
5.51 %), crude protein (17.97 to 26.38 %), crude fat (1.35 to 2.92 %), crude
fibre (4.16 to 8.10 %), carbohydrates (48.99 to 62.63 %), methionine (0.762
to 1.114 g 16 g-1N) and tryptophan (0.60 to 1.08 g 16g-1N).
The in vivo NR assays (plus KNO3) were standardized in terms
of nitrate (100 mM), n-propanol (1 %, v/v) and Triton-X-100 (0.05 %, v/v).
Diurnal variations in NR activity were also observed in trifoliate leaves of a
pigeonpea system. The NR activity from various leaves of 21-day-old
level of
plants indicated that the highest) NRA was observed in ICPL-87, while the
lowest in ICPL-87119. The cotyledonary leaves had the highest NR
activity, followed by first and second trifoliates in all the genotypes differing
in maturity. The observed significant positive correlation between NRA in
different leaves and protein content in the grains of these pigeonpea
genotypes suggested that the genotypes with higher protein content and
NR activity such as ICPL-87 and PT-01-77 can be selected for further
varietal improvement programmes. The highest NRA was largely confined
to petioles indicating it as the major site of nitrate reduction and
assimilation in pigeonpea, which was closely followed by leaves and
stems. The roots and root nodules, however, had comparatively low level
ofNR.
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