Effect of light and benzyladenine on dark-treated growing rice leaves (Oryza sativa). I. Changes in chlorophyll content and catalase activity

Light- and benzyladenine-induced reversal of the changes in chlorophyll content and catalase activity were studied in the attached first leaf of Oryza sativa L. cv. Bala, kept in darkness for different periods before maturation. Dark treatment caused a decrease in chlorophyll content and catalase activity at all times. Light treatment of dark-incubated seedlings at different periods before maturation reversed the dark-induced effect on chlorophyll content, catalase activity and dry weight and also caused a further rise in chlorophyll content compared to initial values. In darkness, the application of benzyladenine replaced the light effect in maintaining catalase activity. Chlorophyll content was also maintained by initially applied benzyladenine. Benzyladenine did not promote the photoinduced maintenance and increase in chlorophyll content and catalase activity at any time. Treatment with hydrogen peroxide, glycolate and amizol resulted in an accelerated chlorophyll breakdown and had varied effects on catalase levels. Chlorophyll decrease due to peroxide accumulation was to some extent reversible by benzyladenine, but the hormone had no effect on the peroxide-induced decrease in catalase activity. Development of catalase is light dependent. Benzyladenine stabilises the enzyme but has no effect on its synthesis.