Effects Of Ozone And Cadmium Stresses On Eco-physiological Traits And Grain Quality In Winter Wheat

This study was conducted in the Research Station of Farm Ecosystem of Shandong Agricultural University in 2008 and 2009. Two winter wheat cultivars including JM22(ozone sensitive) and ND311(ozone tolerant) were grown in plastic plots in the presence of ozone (O₃) and/or cadmium (Cd) to explore the combined effects of O₃ and Cd on the growth, photosynthesis, antioxidative enzyme system, uptake of mineral elements, yield and grain quality of winter wheat. The main conclusions were as followed:1 Effects of O₃ and Cd on the growth of wheat seedlingO₃ decreased plant height (-14.2%), root length (-12.2%) significantly (p<0.05), while the visible injury was higher (145.3%) compared to the control. The relative water content didn't reduce significantly. The plant height, root length, and relative water content reduced significantly in +Cd treatment. The reductions of plant height, root length, and relative water content were 31.2%, 60.0%, 19.6%, respectively, indicating the damage of Cd to plants were enhanced by O₃. O₃ didn't influence the plant height, root length, relative water content and visible injury of ND311 significantly. The growth of ND311 was inhibited the most in O₃+Cd treatment, which has the same trends as JM22.2 Effects of O₃ and Cd on the reactive oxygen metabolism and membrane peroxidation of wheat seedlingThe SOD, POD, CAT activity and MDA content of JM22 were 46.5%, 50.0%, 47.8%, and 60.0% higher, respctively compared to the control. However, O₃ didn't influence SOD and CAT activity of ND311 significantly. Cd increased the SOD, POD, CAT activity and MDA content of the two cultivars significantly. The SOD, POD, CAT activity of JM22 were 100.2%, 75.4%, 161.2% higher respectively in O₃+Cd treatment, while the MDA content was still 90.0% higher, indicating the increased antioxidant activities might not be enough to completely overcome the adverse effects of both pollutants. 3 Effects of O₃ and Cd on the photosynthesis of flag leaf after anthesisThe photosynthetic rate, stomatal conductance, and transpiration rate of the two cultivars decreased under +O₃, +Cd, O₃+Cd treatment compared to the control. The differences become larger while the treatment continued and become significant at 14th day after anthesis. ND311 had similar trend in +O₃ treatment, but the difference was not significant. O₃+Cd decreased the photosynthetic rate, stomatal conductance, and transpiration rate of the two cultivars significantly, but the difference was not significant compared to +Cd treatment.The maxmimal photochemical efficiency, electronic transportation rate, and photochemical quenching of the two cultivars decreased under +O₃, +Cd, O₃+Cd treatment compared to the control. The differences become larger while the treatment continued and become significant at 21st day after anthesis. ND311 had similar trend in +O₃ treatment, but the difference was not significant. O₃+Cd decreased the maxmimal photochemical efficiency, electronic transportation rate, and photochemical quenching of the two cultivars significantly, but the difference was not significant compared to +Cd treatment.4 Effects of O₃ and Cd on the mineral elements content in winter wheatThe Cd contents in different parts of wheat were diverse following this sequence: root > stem and leaf > grain. The Cd content in O₃+Cd treatment was higher copared to +Cd treatment, indicating O₃ enhanced the uptake of Cd in plants. The B, Mg, P, K, Mn, Zn content of root, stem and leaf, and grain in JM22 were reduced significantly in +O₃ and +Cd treatment. For example, the B content in grian, stem and leaf, and root of JM22 reduced 11.3%, 16.2%, 14.6% significantly (p<0.05). The effects of Cd on the mineral elements could be classified into two categories. The first one is inhibition effect, which means that Cd decreased the B, Mg, P, K, Mn, Zn content of grain, stem and leaf and root. For instance, Cd reduced the Mg content in grain, stem and leaf and root in JM22 8.8%, 15.9%, 16.8%, repectively. The other was enhancement effect, which means that Cd increased the Fe, Ca, Cu content in grain, stem and leaf, and root. For example, Cd increased the Ca content in grain, stem and leaf, and root in JM22 14.1%, 18.8%, 33.8%, respectively.5 Effects of O₃ and Cd on the yield and grain quality of wheatO₃ significantly decreased grain number per spike, grain weight per spike of JM22 5.2%, 7.4%, respectively, but didn't have significant influence on 1000-grain weight and harvest index. ND311 had the same trend in +O₃ treatment. Cd significantly reduced grain number per spike of the two cultivars 20.0%, 15.0%, respectively, grain weight per spike 26.0%, 18.2%, respectively, and 1000-grain weight 21.1%, 15.1%, repectively.O₃ decreased starch content, protein content and white of JM22 significantly. For instance, the protein content reduced 4.8% compared to the control, but O₃ didn't have significant influence on starch content, protein content, and white. Cd significantly reduced starch content, protein content, and white of JM22 3.1%, 7.0%, 2.4%, respectively.