Analysis of Grain Filling Process to the Varied Meteorological Conditions in Winter Wheat Cultivars

Abstract

This paper describes e#ects of varied meteorological conditions on the grain filling periods, stabilities of yield and quality of winter wheat cultivars with di#erent maturity characteristics (cv. Ayahikari, Norin0+, Bandowase, Tsurupikari). In the field experiments, the meteorological treatments were made during the first heading time on +1 April ,**+ and the middle heading time on ,. April ,***. Air temperature, global solar radiation and soil moisture were controlled using a rain shelter, cheesecloth and irrigation system. The growth speed and growth period of wheat grains varied among four winter wheat cultivars, depending on meteorological conditions. The growth speed increased within +2.. of mean air temperature over the -* days after the anthesis. On the other hand, it was found that the growth speed of wheat grains and the maximum number of wheat grains (Ymax) decreased greatly with the ....῍ interception of global solar radiation. Logistic functions were fitted to the relationship between the relative thousand-kernel-weight (Y/Ymax) and the total integrated temperature (`Ta) after heading for all treatment conditions.The maximum weight of grains (Ymax) achieved at the harvest time varied somewhat clearly among four winter wheat cultivars and meteorological conditions. Multiple regression analysis showed that the grain yield (Ymax) of four wheat cultivars correlated positively with daily mean solar radiation. It was also found that the cultivar Ayahikari had a highly significant negative correlation between its grain weight and soil moisture. Namely, the grain weight of high soil moisture plot with pF+./ was lower by about 3῍ than that of a control plot with pF-./. On the other hand, the grain yield of cultivar Norin0+ responded inversely to a wet environment, indicating that its grain weight was higher for high soil moisture and high wet-bulb temperature than for a dry environment. The grain yield of early varieties of Bandowase and Tsurupikari increased with the increasing temperature di#erence (TdΐTw). Ash and protein contents of wheat grains in the restricted global solar radiation plot and higher temperature plot were higher than those for the control plot, independently of the four winter wheat cultivars.