Abstract
The effects of sulfur dioxide (SO2) on the appearance of visible injury and photosynthesis in leaves of sunflower plants (Helianthus annuusL. cv. Russian Mammoth) grown in a phytotron greenhouse were examined with respect to leaf maturity. Five weeks old plants were exposed to 2.0 μl l-1SO2for 6 hr and the degree of visible injury was measured to demonstrate the leaf age/SO2sensitivity variation. Young leaves were more SO2-tolerant than old ones.
Studies were also conducted to elucidate the relationship between concentrations and leaf maturity with respect to the SO2-induced inhibition of photosynthesis in sunflower leaves, when the relative rate of photosynthesis was logarithmically plotted against time, the line was separated into two straight lines. To describe the degree of inhibition of photosynthesis, the slopes of these lines (designated as the inhibition coefficients) were calculated. The initial coefficient was always higher than the second one, and both coefficients were leaf-age dependent.
