Effects of elevated O₃ concentration on winter wheat and rice yields in the Yangtze River Delta, China.

The effects of a continuing rise of ambient ozone on crop yield will seriously threaten food security in China. In the Yangtze River Delta, a rapidly developing and seriously air polluted region in China, innovative open-top chambers have been established to fumigate winter wheat and rice in situ with elevated O(3). Five years of study have shown that the yields of wheat and rice decreased with increasing O(3) concentration. There were significant relationships between the relative yield and AOT40 (accumulated hourly O(3) concentration over 40 ppb) for both winter wheat and rice. Winter wheat was more sensitive to O(3) than rice. O(3)-induced yield declines were attributed primarily to 1000-grain weight and harvest index for winter wheat, and attributed primarily to grain number per panicle and harvest index for rice. Control of ambient O(3) pollution and breeding of O(3) tolerant crops are urgent to guarantee food security in China.