BIOCHEMICAL-CHANGES IN LOW-IRRADIANCE TOLERANT AND SUSCEPTIBLE RICE CULTIVARS

In the topmost leaves of low-irradiance (LI) tolerant CO 43 and LI sus ceptible IR 20 rice cultivars, the contents of chlorophyll (chl) a and b and carotenoids and the Hill reaction activity increased under LI. The increase was greater in cv. CO 43 than that in cv. IR 20, and in C hl b than in Chl a. The contents of soluble proteins and reducing suga rs and nitrate reductase activity of the leaves decreased while the co ntent of non-reducing sugars increased due to shading. The decrease in reducing sugars was greater in cv. CO 43 than in cv. IR 20. On the ot her hand, the decrease in soluble proteins and nitrate reductase was m uch less in cv. CO 43 as compared with cv. IR 20.