Destruction of enzymatic activities of corn and soybean leaves exposed to ozone

摘要

Experiments were conducted to determine the effects of a single ozone exposure on selected enzymatic activities and chlorophyll contents of corn and soybean seedlings. Both nitrite reductase activity and chlorophyll content of the seedlings were found to be quite sensitive to ozonation and were seen to decrease as much as 50 after exposure to 80 parts per hundred million (pphm) ozone. After exposure to lower levels of ozone, less-pronounced decreases were observed. Nitrate reductase activity was reduced only after exposure of seedling leaf tissues to high concentrations of ozone. These results are discussed in relation to the concept of a two-phase response to oxidant exposure. The first phase is at the chloroplast level and is quite sensitive to the low as well as the high concentrations of ozone; the second is at the cellular level and is relatively resistant to all but the highest ozone concentrations.