NUTRITIONAL EVALUATION OF GRAINS AND ASSESSMENT OF NITRATE REDUCTASE POTENTIAL IN TWELVE AMARANTH (Amaranthus cruentus L.) CULTIVARS
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Date
1998
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Mahatma Phule Krishi Vidyapeeth, Rahuri.
Abstract
The present investigation aims at evaluating the
proximate composition of grains of twelve amaranth cultivars.
In addition, the nitrate reductase (NR) activity from the
leaves of amaranth plants was standardized by an in vivo
method. The genetic potential of NR activity in twelve
amaranth cultivars was also estimated. Further, it was desired
to know the distribution of NR activity in different plant
parts such as leaves, stems, petioles and roots in 60-day-old
amaranth. The amaranth seedlings were grown in soil-filled
pots under normal day light conditions at the Department of
Biochemistry, Mahatma Phule Krishi Vidyapeeth, Rahuri during
the months from August to December, 1997. The proximate composition indicated that crude
protein content of the grains of amaranth cultivars varied
from 12.34 to 16.86 per cent. The crude fat content ranged
from 4.06 to 6.38 per cent, while tho crude fibre content
varied from 2.90 to 4.34 per cent. The total ash content in
the amaranth grains ranged from 1.97 to 2.93 per cent. The
variation in carbohydrates content, determined by difference,
was from 63.13 to 68.78 per cent. Calcium and phosphorus
contents of the amaranth grains varied widely from 127.63 to
203.20 mg/100 g and 310.33 to 470.00 mg/100 g respectively.
The iron content of the grains also showed a wide variation
from 8.58 to 17.00 mg/100 g. Thus, the proximate composition
of the amaranth grains reveals that the grains are the major
source of proteins and minerals, viz., calcium and iron. The
NR activity in amaranth leaves was determined by an in vivo
method and the standardized infiltration media (5.0 ml) for
determination of NR activity/in amaranth leaves included :
nitrate, 100 mM; n-propanol (1 %, v/v) and Triton-X-100 (0.05
%, v/v) together with 100 mM Na-Pi buffer (pH 7.5). The enzyme
NR exhibited diurnal rythms in amaranth leaves. The average NR
activity which was low at 7.00 a.m. in the morning increased
rapidly as the day advanced until it reached a maximum level
at 1.00 p.m. The NR activity, however, declined during the
afternoon hours, reaching a minimum level in the evening at 7.00 p.m. The evaluation of the potential of the NR enzyme
exhibited the highest NR activity in the cultivar Rasana-2
while the lowest was in AG-67. The significant
correlation between NR activity in leaves and grain protein
content of the twelve amaranth cultivars indicated that the
cultivars with higher protein and NR activity such as AG-114
and Rasana-2 could be selected for breeding high protein grain
genotypes. The highest NR activity in 60-day-old amaranth
plants was located in petioles, indicating that petioles ace
the major site of nitrate assimilation in amaranth, followed
by leaf, stem and root in the decreasing order.
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