EFFECT OF TRIACONTANOL IN FLOODED ERYTHRINA VARIEGATA SEEDLINGS .2. CHANGES IN (CO2)-C-14 FIXATION, AND RIBULOSE-1,5-B-ISOPHOSPHATE CARBOXYLASE, PHOTOSYSTEM AND NITRATE REDUCTASE ACTIVITIES

The effect of spraying triacontanol (Tria) solution (1 g m-3) on CO-14 (2) fixation, ribulose-1,5-bisphosphate carboxylase (RuBPC), nitrate r eductase (NR) and photosystem (PS) activities in waterlogged Erythrina variegata Lam. was investigated under field conditions. Seedlings exp osed to flooding for 10 d showed a significant reduction in CO-14(2) f ixation, and in NR, RuBPC and PS2 activities. Electrophoretic analysis of thylakoid polypeptides indicated a significant loss of 47, 43, 33, 25, 23, 17 and 15 kDa polypeptides in flooded seedlings. However, the application of Tria partially ameliorated the effect of flooding and promoted the above activities. The site of flooding injury was at the oxidation site of PS2 prior to the hydroxylamine donating site and per haps close or after the diphenylcarbazide donating site. The increase in the RuBPC activity in Tria-treated seedlings under flooding correla ted well with the changes in CO2 fixation rate.