CO2 FIXATION RATE AND RIBULOSE DIPHOSPHATE CARBOXYLASE ACTIVITY IN C3-PLANTS AND C4-PLANTS GROWN WITH NORFLURAZONE

We have studied the effect of norflurazone on RuDP-carboxylase conten t and activity, CO2 fixation rate, soluble protein, and carotinoids an d chlorophylls in leaves of C3- (barley, wheat, beans, radish) and C4- plants (maize) grown under low illumination (0.12 and 0.4 W/m2). RuDP- carboxylase content, soluble protein, and CO2 fixation rate are increa sed in C3-plants grown with norflurazone at low illumination (0.12 W/m 2), while RuDP-carboxylase activity remains unchanged Enhancement of c hloroplast photodestruction in plants grown with norflurazone at high illumination results in a decrease in RuDP-carboxylase content, while RuDP-carboxylase activity and CO2 fixation rate are increased. RuDP-ca rboxylase content is greatly decreased in leaves of maize grown with n orflurazone at 0.12 W/m2, but RuDP-carboxylase activity and CO2 fixati on rate are increased Maize is probably more resistant to high illumin ation due to the CO2 recycling system in C4-plants. RuDP-carboxylase m ay function when PS II is significantly inhibited Photodestruction is partially reversible in 7-day-old plants grown from seeds pretreated w ith 6-benzylaminopurine due to increase in soluble proteins and pigmen ts. We found that norflurazone and 6-benzylaminopurine have antagonist ic effects on CO2 fixation rate and RuDP-carboxylase activity.