Studies on the Mechanism of Injurious Effects of Toxic Gases on Crop plants : XIII. Effects of ozone in the air on the apparent photosynthesis of corn, rice and peanut plants

Abstract

Recently air pollution caused by photochemical oxidants has produced the very serious subjects, because of a wideness of their polluted area and being injurious to many crop plants. The experiments were carried out to elucidate the effect of ozone on apparent photosynthesis during and after the exposure to ozone and the visible injuries to corn, rice and peanut plants. Apparent photosynthesis of 3 kinds of plant used in this experiment decreased to a considerable extent when exposed to a higher concentration than 0.5 ppm, although a slight decrease was observed even at 0.1 ppm. Both photosynthesis rate by ozone and its extent lowered could be arranged on the following order, peanut>rice>corn plant; and the visible injury was also in the same order. Furthermore, it was investigated that whether the decrease in photosynthesis by ozone treatment is recovered or not, after the plants were released from the ozone. The photosynthesis of corn plant did not entirely recover for 2 hours after stop of ozone treatment, but that of rice plants showed a clear trend to recover. Photosynthesis of peanut plants did not recover but continued to decrease for 1 hour even after ozone treatment had been stopped. The photosynthesis in peanut plant decreased in proportion to the increase in the visible injury. 0n the other hand, visible injuries in the other species became apparent when photosynthesis decreased by 70% in the rice and 65% in the corn plants. From these results it was concluded that the degrees of invisible injury, judging from the photosynthetic rate influenced by ozone, were in the following order, rice>corn>peanut plants