EFFECT OF SALICYLIC-ACID ON THE SYNTHESIS OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE IN BARLEY LEAVES/

Hordeum vulgare L. (cv. Alfa) was grown for 7 days over a range of sal icylic acid (SA) concentrations (100 mu mol/L-1 mmol/L), and the effec t on the level of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rub isCO) was examined. The treated plants showed a decrease in the level of total soluble protein, in particular in the level of RubisCO. In th e presence of 1 mmol/L SA the level of total soluble protein on a fres h weight basis was about 68% of the control, whereas the level of Rubi sCO was about 50% that of control plants. The percentage of inhibition on the small subunit was higher, as a result of which the small/large subunit ratio was lower for the experimental variants. When 7-day-old barley seedlings were supplied with SA through the transpiration stre am for 24 h no changes in the levels of total soluble protein and Rubi sCO were observed. The influence of SA on the synthesis of RubisCO was followed by in vivo labelling with a C-14-amino acid mixture (C-14-AA M). Results demonstrated that SA inhibited both the synthesis of total soluble protein and, more pronounced, the synthesis of RubisCO.