[Impacts of elevated atmospheric ozone concentration on flag leaf microscopic structure of wheat: a field study with FACE system].

By using FACE (Free-Air Controlled Environment)-ozone system, a field plot experiment was conducted in 2008-2009 to study the effects of elevated ozone (O3) concentration on the flag leaf microscopic structure, chlorophyll content, and grain weight of wheat. Two treatments were installed, i. e., ambient O3 and 150% of ambient O3, and four winter varieties, i. e., Yannong 19, Yangmai 16, Jiaxin 002, and Yangfumai 2, were taken as the test materials. At anthesis, elevated O3 concentration had a slight damage to the flag leaf microscopic structure. The mesophyll cell and chloroplast structure began destroying, and the grana lamellae started breaking and loosing. Twenty-one days after anthesis, the differences in the leaf microscopic structure between the two treatments became significant. Under elevated O3, the flag leaf senescence was accelerated, with the endomembrane system disintegrated, grana lamella disappeared, and corpus adiposum inside chloroplast broken down, resulting in a significant decrease of the chlorophyll content, photosynthesis rate, and grain weight at maturing stage. Significant difference was observed among the test varieties in their responses to elevated O3. Jiaxin 002 was tolerant, while Yangfumai 2 was sensitive to the ozone stress.