[Effects of all-day warming on growth, development and yield of winter wheat cultivars bred in different periods].

A field experiment was conducted to study the effects of all-day warming on the growth, development and yield of winter wheat cultivars bred in different periods under free air temperature increase (FATI) in Xuzhou and Danyang, Jiangsu Province. Warming decreased the effective tillers by 5.2% and 9.6%, and the ineffective tillers by 15.6% and 9.7% in Xuzhou and Danyang, respectively. Plant height under FATI was higher in Xuzhou, but lower in Danyang than that of the control. Plant heights of the late cultivars were lower than that of the early cultivars. Warming increased the leaf area index for all cultivars. Warming increased the net photosynthetic rates of the winter wheat cultivars except for those bred in 1950-1960s and 1980s in Xuzhou and 1950-1960s and 1990s in Danyang. There were different changing tendencies of the night respiration rate among the winter wheat cultivars bred in different periods. Aboveground biomass and harvest index of all cultivars increased under FATI. Harvest index of late cultivars was higher than that of early cultivars in Xuzhou and Danyang. Growth period of different cultivars under FATI was all shortened, av- eragely by 3.2 and 4.1 d in Xuzhou and Danyang, respectively, mainly due to shortening the preheading stage (averagely by 7.5 and 8.5 d in Xuzhou and Danyang, respectively) and prolonging the filling stage (by average 4.3 d). Except for 1950-1960s cultivars in Xuzhou, the grain yields increased under FATI, averagely by 21.0% and 14.1% in Xuzhou and Danyang, respectively. Statistical analysis of variance showed that the warming-induced wheat yield changes were due to the changes in grain number per spike and effective spikes in Xuzhou and the change in 1000-grain mass in Danyang, respectively.