The .in and Vivo Nitrate Reeducates Activity in Tef (Eragrostis Tef (Zucc.) Trotter) Under Different Assay Conditions
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Date
1982-06
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Addis Ababa University
Abstract
The presence, substrate inducibility and regulations of
the enzyme nitrate reductase (NADH: Nitrate Oxidoreductase, . .
E.C. 1.6.6 .• 1)(NR) of both dark-grown and light-grown tef plants
(Eragrostis ~ (Zucc.) 'rrotter) were studied. The relative
merits of the in vivo and in vitro methods of assay for the
enzyme were evaluated. Major factors affecting nitrate
reductase activity and the distribution of the enzyme in both
the dark- and light-grown plants were investigated.
Nitrate and urea induced the formation of nitrate reductase
in 5-day-old dark-grown tef plants; and the activity of the
enzyme was predominantly associated with the roots. In the
glasshouse-grown plants, however, both the ammonia-type and
the nitrate-type nitrogen sources elicited NR activity although
nitrate was still superior in enzyme induction; and the leaves
were found to be the major centeres for nitrate reduction.
A pH of 7.6 was found to be optimal for an in vivo NR
activ~ty of tissue obtained from leaves of light-grown tef
plants.
Diurnal variations in NR activity were observed, with peak
activity at mid-day, suggesting that the enzyme is under the
control of light •. Logging tef plants for 11 days after 10 days of maturation
did not substantially affect the enzyme activity. It
was observed that tef seedlings discriminate between ammonium
and nitrate during their early stages of development by
preferentially assimilating the former when given in combination
with the latter. These findings suggest that tef plants can,
at least at their early stages of development, successfully
withstand reductive soil conditions.
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Biology