Duration of Grain Filling and Kernel Weight of Wheat as Affected by Temparature1

Abstract

Once kernels are set, cereal grain yields are proportional to kernel weight. Thus environmental effects on kernel size merit better understanding as a source of yield variability.Plant phenology was observed, environmental conditions were monitored, and kernel weights were determined for wheat during two seasons at 26°N. Lat. These observations provided data sets for relating mean daily temperature during grain filling (from the beginning of flowering to mealy ripeness of the kernels) to kernel weight and to duration of grain filling.The data indicate a 3.1 day shortening of grain filling per degree C increase in mean daily air temperature during grain filling which compares with 2.8 days C^‐1 for seven studies reported in the literature. Kernel weight in this study decreased 2.8 mg kernel ^{‐1 C‐1} compared with 1.5 mg for each degree C increase in temperature for seven studies in the literature.We concluded that temperature is pacing plant senescence and that shortening the duration of grain filling is its common manifestation in commercial winter and spring wheats. Temperature, when in excess of about 15 C, apparently explains the dependence of 1,000 kernel weight on grain filling duration.The findings imply that genetic variability in plant senescence and grain filling rates need to be searched for and exploited to help stabilize the kernel size component of yield.