As a consequence of increases in aerosols, air pollutants and population density, dimming or shading have become major challenges to crop production in China. And during the last several decades, significant increase in the concentrations of tropospheric ozone (O₃) have been reported. The increased tropospheric O₃ concentrations and induced solar irradiance may concomitantly occur and lead to reductions in yield of crops and economic plants. Especially, there are a great variety large-scale industries in the Yangtze River delta where is the major producting area of winter wheat. Which will enlarge the high-potential risks on growth and yield of winter wheat for their heavy air pollution.
Although the influences of each individual stress on plant performance have been widely studied, much less is known about the interactions of O₃ stress and solar irradiance on the winter wheat. In order to analysis this focus question in the varied growth stages of crop including jointing stage, booting stage, blooming stage, grain filling stage and mature stage, a experiment based on open top chambers (OTC) was conducted from November 18 of 2010 to June 5 of 2011 in Nanjing University of information Science & Technology (32°14' N, 118°42' E), located at North suburb of Nanjing, Jiang Su Province. And the YangMai13 as a tested variety was a pillar in our study.
Winter wheat are exposed to unfiltered air (CK), shaded 40% of nature solar irradiance (T₁), enhanced increased O₃ concentration (100nL/L O₃, T₂) and combined treatment (100nL/LO₃ +shading 40%, T₃). The results are showed as follows: the treatments of T₁, T₂ and T₃ all cause the changes of growth period and the plant premature aging. The grain filling stage and the growth period are all shortened in T₂ treatment; T₁ and T₃ treatments, however, prolong the growth stage of winter wheat. In addition, a significant reduction of dry matter production under T₁, T₂ and T₃ treatments compared to CK (P<0.05) with declined 23.37% (P<0.05), 35.61% (P<0.05) and 55.29%(P<0.05), respectively. Besides, compared with CK, the grain weight、1000-grain weight and ear weight of each treatment are all reduced(P<0.05) under the treatments. And it clearly shows that ear number of T₁ and T₃ are both declined (P<0.05). We can preliminary conclude that compared with shading and O₃ alone, the combination between shading 40% and O₃ concentration enhanced can enlarge the negative effects on wheat growth and yield. Moreover, the effects of growth and growth period of under the combination are closer to 40% solar irradiance treatment. And the major reason for declined grain weight under the combination is decrease of grain filling rate instead of decreases of grain filling duration. It also obviously demonstrated that the number of spikelet, the grain weight per spike and the 1000-grain weight of the composite treatments decreased significantly (P<0.05) 35.15%, 39.32% and 34.38%, separately. As a result, the grain yield decreased by 64.65% compared with the control, but the value is less than two factors accumulate alone.