EFFECT OF SIMULATED ACID-RAIN ON 14CO2 FIXATION, RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE AND NITRATE AND NITRITE REDUCTASES IN VIGNA-SINENSIS AND PHASEOLUS-MUNGO

In greenhouse experiments the effect of simulated acid rain (mist of H2SO4) treatment on (CO2)-C-14 fixation, ribulose-1,5-bisphosphate carboxylase (RuBPC), nitrate reductase (NR) and nitrite reductase (NiR) activities in Vigna sinensis L. and Phaseolus mungo L. was investigated at different pH. Seedlings exposed to acidic mists of pH 5.6, 4.0 and 2.0 for 5 d showed significant reduction in (CO2)-C-14 fixation, RuBPC, NiR and especially NR activities. Sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) of crude leaf extracts of RuBPC indicated a significant loss of 55 and 15 kDa polypeptides at pH 2.0 in both the crop plants. The reduction in the RuBPC activity in seedlings grown under acidic mists correlated well with the CO2 fixation. NR activity was affected more than the NiR activity.