Effect of High Temperature Stress During Grain Filling Period On Grain Yield and Physicochemical Properties of Wheat (Triticum aestivum L.).

Korean wheat cultivars, 'Jopoom', 'Keumkang', and 'Chokwang', were planted on 13 October in 2011, and four temperature gradient, control (ambient temperature in field plot, 19C, Tc), Tc+0.8C, Tc+1.5C and Tc+3.6C, were artificially created by controlling the green house system. Total dry weight of wheat plant was increased by high temperature during grain filling period. However, high temperature stress led to induction of white ears in wheat. The length, width, and thickness of wheat grain were decreased significantly with increasing the ripening temperature. The development of width and thickness were more decreased by high temperature than the length of wheat grain. The 1,000-grain weights decreased significantly by 10.3% at Tc+0.8C, 18.9% at Tc+1.5C, and 39.1% at Tc+3.6C, respectively, as compared to the control. The decrement of carbon to nitrogen ratio (C/N), and the free sugar contents (fructose, glucose, sucrose & maltose) in wheat grain explained that carbohydrate assimilation during grain filling period was restricted by high temperature. The slight increments of protein content at Tc+3.6C, and lipid content at Tc+1.5C, indicate that high temperature during grain filling period was not favorably influence to promote the protein and lipid synthesis, but affected to inhibit the carbon metabolism. The composition of unsaturated fatty acid was increased with increasing the ripening temperature. Among the unsaturated fatty acids, linolenic acid was the most affected by high temperature.