Abstract: Effects of temperature during grain-filling on chain length distribution and structure characteristics of 4 early-season indica rice cultivars were investigated under the environment-controlled conditions. The plants at flowering stage were subjected to two temperature treatments until maturity (the mean daily air temperature, 22℃ and 32℃ for optimum temperature treatment and high temperature treatment, respectively). The result showed that high temperature during grain-filling period significantly decreased the long B-chain content and increased the intermediate B-chain content. But the effect of high temperature on other starch chains appeared to be cultivar-dependant. The crystalline characteristics of rice starch were also affected by temperature during grain-filling. Period.The intensity at 18°2θ of X-ray diffraction pattern of rice samples under high temperature was higher than those under optimum temperature, though all rice starches performed A-crystalline type. Moreover, the intensity at 17°2θ was positively correlated with intermediate B-chain content and negatively correlated with long B-chain content.

Key words: Rice (Oryza sativa L.), Temperature, Starch, Chain length distribution, Crystalline structure