Effects Of High Temperature On The Physiological Characteristics And Rice Quality In Grain-filling Stage

The rice varieties of Koshihikari (Japonica), Akita Komachi (Japonica), Gang-you527 (Indica hybrid rice) and IR72 (Indica) were used to study the effects of high temperature treatment on physiological characteristics and rice quality during grain-filling stage. The results were as follows.1. Effect of high temperature on physiological characteristicsChlorophyll SPAD value of sword leaves decreased under high temperature treatment, and malondialdehyde (MDA) content of sword leaves increased, while with the extension of the treatment time, malondialdehyde content continued to rise rapidly. Both normal temperature and high temperature MDA content of IR72 were significantly lower than the other three varieties.The soluble sugar and protein content average levels of functional leaves decreased under high temperature treatment. All varieties stem sheath soluble protein content were lower than those under normal temperature, the starting point of stem sheath soluble protein content lower than that under normal temperature as well.2. Effect of high temperature on yield charactersThe distinction of effective panicle were non-significant under high temperature treatment. Compared to the control, the common grains (per panicle) of Gang-you527 decreased, with the very significant difference, while the others were insignificant. Actual grains (per panicle) of Akita Komachi and IR72 decreased significantly, with Gang-you527 showing very significantly. The seed setting rate of Gang-you527 and ER72 decreased, with very significant distinction. 1000-grain weight of Koshihikari and Akita Komachi decreased significantly, with IR72 showing insignificant difference. Compared with the control, the yield of varieties decreased, with the very significant difference or significant difference.3. Effect of high temperature on rice quality3.1 Effect of high temperature on milling quality Compared to the control, the distinction of the brown rice rate, milled rice rate of varieties were insignificant under high temperature. The head rice rate of Koshihikari, Akita Komachi and Gang-you527 decreased very significantly, and IR72 decreased significantly.3.2 Effect of high temperature on appearance qualityCompared to the control, there was no significant difference on length of grain under high temperature. The width of grain decreased significantly on Koshihikari and IR72, and no significant on Akita Komachi and Gang-you527. The length breadth ratio increased significantly on Koshihikari and IR72, and no significant on Akita Komachi and Gang-you527. The chalky rate also increased, and there was very significant effect on Koshihikari, Akita Komachi and Gang-you527. With significant difference on IR72.3.3 Effect of high temperature on eating and cooking qualityThe amylose content of grain decreased under high temperature, and there was very significant difference on Koshihikari and Gang-you527. With significant difference on Akita Komachi and IR72.The changes of RVA value under high temperature were as follows. The peak viscosity of Japonica rice (Koshihikari, Akita Komachi) increased, but Indica rice (Gang-you527, IR72) decreased. The trough viscosity and final viscosity of varieties decreased. The breakdown value of Koshihikari increased significantly, and the others has no significant difference. The setback value of Japonica rice (Koshihikari, Akita Komachi) decreased significantly, but Indica rice (Gang-you527, IR72) decreased. The consistence of Koshihikari, Akita Komachi and Gang-you527 decreased, but that of IR72 increased. We had a conclusion. Japonica rice varieties had better eating quality with higher peak viscosity, lower set back value under high temperature treatment, and Indica rice varieties opposable.The changes of taste sense identification value under high temperature were as follows. The appearance values of Akita Komachi were negative, Koshihikari, Gang-you527 and IR72 showed positively. Fragrance values of Koshihikari and IR72 were negative, but they were positive values on Akita Komachi and Gang-you527. Palatability, adhesiveness, hardness and synthetic evaluation values of Koshihikari and Akita Komachi were negative, Gang-you527 and IR72 showed positively.3.4 Effect of high temperature on nutrition qualityThe protein content of varieties increased significantly under high temperature, this result showed that it was conducive to accumulation of protein under high temperature. The changes of amino acid (AA) content as follows. The total AA content increased except individual AA. The total AA content of indica rice varieties increased more than those of Japonica rice varieties.