[Response of dry matter partitioning coefficient of summer maize to drought stress in North China].

The dry matter partitioning coefficient (PC) reflects the distribution and accumulation of dry matter in crop organs. Understanding the responses of PC to drought stress is fundamental for understanding crop development under drought stress. Using field data collected under drought stress conditions during the period 2013-2015 at three sites (Xiajin, Shandong; Gucheng, Hebei; and Yuncheng, Shanxi) in North China, we quantified the effects of different drought stress intensities on the PC of stems, leaves and ears during the development stages (from emergence to jointing, from jointing to tasseling, and from tasseling to maturity). The results showed that PC of stems, leaves and ears showed significant quadratic relationships with relative soil moisture during all stages. Leaf PC was increased by 0.04-0.09 during the grain-filling stage under light and moderate drought stress, and was increased by 0.17 during the tasseling stage under sever drought stress. On the contrary, drought stress had negative effects on the ear PC. With the increases of drought stress, less dry matter was allocated to ears. Under light to severe drought stresses, ear PC was decreased by 0.08-0.34. However, no consis-tent pattern was observed for the effects of drought stress on stem PC: negative effects were observed during the vegetative growth stage and positive effects were found in the mature stage. Overall, the degree of the responses of crop PC to drought stress under different phenology stages was in the order of grain-filling stage (positive) > tasseling stage (negative) > seedling stage (negative).