Impacts Of Nighttime Warming On Rice Growth And Development

Climate warming is the main characteristic of global climate change. Since rice(Oryza sativa L.) is one of the important cereal crops in the world, study on the impacts of climate warming on rice production is of great significance to the evaluation of future food security in China and even the world.Research need to be carried out in different ecological regions to clarify the actual response of rice growth and development as well as its regional and variety differences. Therefore, we applied two kinds of warming systems i.e. the Passive Nighttime Warming(PNW) system and the Free Air Temperature Increase(FATI) system that would simulate the actual range of global temperature change.Representative sites in double rice, rice-wheat rotation and the Northeast single rice systems and 8leading varieties released during 1970s-2000 s of Jiangsu province(rice-wheat rotation area) were adopted to investigate the effects of nighttime warming on rice growth and development. The objective of this study was to clear the actual response and adaptation of rice of various regions and varieties to nighttime warming, with the expectation of providing a theoretical basis for technical innovation under the climate change background. The main results are as follows:(1) Nighttime warming shortened the length of rice growth period with an average reduction of 1.1 d among different regions. The impacts trend varied with growth stages. Nighttime warming obviously shortened the pre-anthesis stage by 2.5 d while tended to extend the post-anthesis stage. There were differences in the warming impact sizes on rice growth period among the regions and varieties.However, no stable changing trend of the differences in warming impacts along with the variety release eras was found.(2) The response sizes of nighttime warming on rice aboveground biomass and grain yield varied with regions. Impacts tendency of the two warming systems was consistent with each other. Nighttime warming decreased annual mean rice grain yield of Wanning late rice, Nanchang early rice, Zizhong,Zhenjiang, and Nanjing by 13.2%, 4.3%, 4.8%, 7.5% and 5.3%, respectively. On the contrary it tended to increase rice grain yield of Wanning early rice, Nanchang late rice, Qiannan and Gongzhuling by6.0%, 11.9%, 6.6% and 11.2%, respectively. Rice aboveground biomass under nighttime warming treatment had similar tendency of change to grain yield. Under nighttime warming treatment, the change tendency of rice grain number and 1000-grain mass were similar to grain yield, while the number of effective panicle tended to increase. Response sizes of biomass and grain yield to nighttime warming were significantly different among varieties released in different eras of the lower Yangtze River.However, we didn’t find stable changing trend of grain yield along with the variety release eras.(3) Rice leaf areas and net photosynthesis rates of Nanchang early rice and Zhenjiang was decreased while which of Nanchang late rice and Gongzhuling was significantly enhanced under nighttime warming conditions. Leaf area of Nanchang late rice and Gongzhuling was significantly enhanced by10.3% and 43.9%, respectively. Net photosynthesis rate of the two sites was significantly enhanced by10.7 and 11.9%, respectively. In addition, nighttime respiration rate of Nanchang early rice, late rice andZhenjiang was enhanced by 101.0%、9.2% and 9.5%, respectively.(4) Effects of nighttime warming on rice grain milling quality and appearance quality were different in different regions. Head milled rice rates of Zhenjiang, Nanchang early rice and Gongzhuling were reduced by 30.3% 、 14.3% and 2.5%, respectively. Otherwise, rice milling quality of other regions tended to increase. Chalky rice rate and chalkiness has the tendency of increase except for Gongzhuling.Nighttime warming promoted the content of grain protein in 2008 and 2010, with the mean increase rate of 5.2% and 4.0%, respectively. However, protein content tended to decrease in 2012, which decreased by 6.3%.