农田冬小麦生长和产量对臭氧动态暴露的响应

 评估臭氧(O₃)污染对农田冬小麦生长和产量的影响是污染生态学和生理生态学研究的重要内容之一。该研究运用开顶式气室(OTC)，对冬小麦‘ 嘉403’(Triticum aestivum cv. Jia 403)进行了O₃动态暴露的田间原位试验。实验设置过滤空气组(CF)、自然大气组(NF)和两个不同浓度的 O₃动态暴露组(DO100和DO150)。结果表明：1) O₃浓度增加，一方面可以改变灌浆期冬小麦叶片气体交换参数的日变化规律；另一方面引起表观 光量子产额、光饱和点和光补偿点等光响应参数的显著降低。这表明灌浆期叶片光合能力的下降是气孔因素和非气孔因素共同作用的结果。2) O₃暴露可以改变小麦形态特征，如植株变矮、叶片衰老加速、 叶面积变小，并最终导致产量大幅下降。

RESPONSE OF PHOTOSYNTHESIS, GROWTH AND YIELD OF FIELD-GROWN WINTER WHEAT TO OZONE EXPOSURE

Aims Ozone is a prominent gas pollutant that adversely affects vegetation, including visible leaf injury, growth and yield reduction. Our objective was to assess photosynthesis, growth and yield responses of field-grown wheat to increased ozone.  Methods We planted winter wheat (Triticum aestivum cv. Jia 403) in 12 plots of 2 m×2 m on 7 November 2005. After the wheat greened, we established 12 open-top octagonal (2.2 m high, 2 m diameter) chambers on 1 March 2006. Except rainy days, wheat was exposed to charcoal-filtered air, unfiltered air, and two treatments with ozone addition (DO100, DO150) from 13 March to 28 April 2006, for 8 h per day, for a total of 30 days. We measured diurnal gas exchange and P_n-PAR response curves of flag leaves at the early grain filling stage (after 25 days exposure to ozone) and components of yield at harvest. Important findings High concentration of ozone altered gas exchange parameters, including stomatal conductance (G_s), leaf photosynthetic rate (P_n), transpiration rate (T_r) and intercellular CO₂ concentration (C_i). Apparent quantum yield (AQY), light saturation point (LSP) and light compensation point (LCP) were significantly decreased, suggesting photosynthetic capacity could also be changed, characterized as reduced photon-saturated photosynthetic rate (P_max). The decrease of photosynthetic activity was probably dominated by non-stomatal factors in combination with stomatal closure. In addition, ozone exposure caused leaf aging and decreases in plant height, ear length and number of grains per ear. Although similar responses were observed in plants exposed to ambient ozone concentration, we found no statistically significant differences at current concentration. We concluded that dynamic ozone exposure detrimentally affects photosynthesis, growth and yield of winter wheat.