ASSESSMENT OF NITRATE REDUCTASE ACTIVITY AND CARBON MONOXIDE SENSITIVITY OF CYTOCHROME c OXIDASE IN THE LEAFLETS OF SOME CHICKPEA CULTIVARS
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Date
1994
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Mahatma Phule Krishi Vidyapeeth, Rahuri.
Abstract
Chickpea seedlings were grown in soil-filled pots
under green house conditions of the Department of Biochemistry,
Mahatma Phule Krishi Vidyapeeth, Rahuri , during the months of
November, 1993 to March, 1994. The experiments were carried
out for the determination of leaflet nitrate reductase activity
by an in vivo method and to monitor the varietal differences if
any in the activity of leaflet NR. Carbon monoxide sensitivity
of cytochrome c oxidase with one min sparging of CO through the
leaf segments/at defined C0:02 ratio^ The effect of 2,4
dinitrophenol (2,4~DNP) on CO-sensitivity in the leaflets of
some chickpea cultivars was also monitored. The in vivo NR assays for chickpea leaflets were
optimized in terms of substrate and n-propanol concentrations
to be added in the infiltration media. The optimum
concentration of KN03 to be added into the infiltration
media, required for maximum in vivo NR activity, was found to
be 100 mM in chickpea leaflets. It was further noticed that 4
per cent (v/v) n-propanol was optimum in the infiltration media
used for the determination of in vivo NR activity. Diurnal
fluctuations were observed in chickpea leaflet NR. The average
NR activity which was low at 8.00 hr in the morning increased
rapidly as the day advanced until it reached a maximum level at
14.00 hr. The NR activity, however, declined during the
afternoon hours and reached a minimum level in the evening at
17.00 hr.
Eight cultivars of chickpea were examined for
carbon monoxide sensitivity of cytochrome c oxidase by sparging
CO for one min through weighed leaflet materials. All the
cultivars were found to be completely insensitive to CO by this
technique. Further a C0:02 ratio of 40 was required to inhibit
cytochrome c oxidase in chickpea leaflets. Pretreatment of
leaves of six chickpea cultivars with 2 mM concentration of
2,4-DNP resulted in the ready response of leaf materials at a
C0;02 ratio of 10 and even at 5.
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