| The activity
of nitrogen-utilizing enzymes, i.e. nitrate reductase (NR), glutamine
synthetase [glutamate-ammonia ligase] (GS), glutamate synthase (GOGAT),
and glutamate dehydrogenase (GDH), during the development of healthy and
malformed panicles of mango cultivars Amrapali and Dashehari was studied
in Lucknow, Uttar Pradesh, India, during 1995-97. Healthy and malformed
panicles were evaluated at stages I (fully developed apical bud), II
(flower bud at inception), III (fully grown panicles prior to full
bloom), and IV (fully developed panicle at the full bloom stage). NR
activity was significantly reduced in normal panicles from stage I to
IV in both cultivars. Nonsignificant changes were observed in the
malformed panicles of Amrapali. In general, the activity of GS and GOGAT
followed the same trend. Contrary to the activity of NR, GS, and GOGAT,
a sharp increase in GDH activity was observed in malformed panicles at
the early stage of panicle development. GDH activity, which was highest
at stage II in both cultivars, declined gradually during stage III and
IV. The higher activity of GDH in malformed panicles indicated the shift
of primary route of ammonia assimilation (GS/GOGAT) at the early stage
of panicle development. Total nitrogen, protein, and nitrate contents
declined with the age of healthy panicle in both cultivars. However,
their level remained higher at the later stage of malformed panicle
development. |
