Abstract
Basing on the facts that the decrease of photosynthetic rate and the increase of respiratory rate of the crop p1ants as exposed to sulfur dioxide, the experiment was undertaken to prove the decrease of dry matter production in rice plants by sulfur dioxide treatment for long Period. The results obtained were as follows ; 1. The number of tillers in rice plants was decreased with an increase in the concentration of sulfur dioxide, but the results of the investigation on the effect of sulfur dioxide on the plant height and leaf age in rice plants by sulfur dioxide did not show any significant differences. 2. Total dry weight (leaves+stems+roots) of rice plants was gradually decreased with an increase in the concentration of sulfur dioxide and an extention of treatment hours for which the plants were exposed to the gas. A typical injury by sulfur dioxide was hot discovered on the leaf-blade and-sheath both during and after treatment. 3. Net assimilation rate and increase rate of dry mattr(ΔW)in the rice plants were markedly decrcased by sulfur dioxide treatment for long period.
