The Effects Of Autumn Low Temperature On Late Rice Yield Formation And Its Risk Zonation In Jiangxi Province

Rice is one of the main food crops in our country, and Jiangxi province is also an important province of rice cultivation in our country, therefore, assuring the safety of Jiangxi rice production is very important to Jiangxi or even to China. Rice planting is highly dependent on the weather conditions, and Autumn Low Temperature is the main natural disaster, which threat to late rice growth in Jiangxi province. Besides, its frequency is also relatively more. Autumn Low Temperature would lead to sterile grain increased, thousand kernel weight decreased, eventually making different levels yields reduce. Based on artificial control experiments, we simulated the effect of Autumn Low Temperature of different days on late rice physiology and ultimately yield. Analysis the temporal and spatial distribution of Autumn Low Temperature by the meteorological data of Jiangxi province, and determining the Autumn Low Temperature disaster risk index distribution. Research results can provide reference for the related mechanism of low-temperature chilling injury of rice research, as well as for Jiangxi index revision of Autumn Low Temperature, disaster prevention and disaster damage assessment, and it also have a positive meaning to protection the safety production of Jiangxi province and China. The main results were as follows:1. Studying on the effect of Autumn Low Temperature on physiological characteristics of late rice, such as photosynthetic characteristics, chlorophyll fluorescence parameters, protective enzymes. The results show Autumn Low Temperature has a significant impact on late rice protective enzyme system, and the protection enzyme activity and MDA content increased with different degrees as the duration of Autumn Low Temperature increased. At the same time, the photosynthetic pigment content decreased, and the effect of short time low temperature stress on the content of chlorophyll-a was not significant. In addition, as the low temperature stress duration increased, the light saturation point decreased, the compensation point increased, and maximum photosynthetic rate decreased significantly, but fluorescence parameters decreased more slowly relatively. The results also showed that the net light photosynthetic rate decline under low temperature was mainly caused by non-stomatal factors.2. We studied on the effect of Autumn Low Temperature on distribution of epigeous biomass and its percentage. The results showed that by the influence if Autumn Low Temperature, the average filling rate decreased, and filling active period also shortened by 5～12d, which result in thousand-grain weight decreased. Biomass of stems, leaves, and spikes varied with the treatment time, and biomass of leaves and spikes reduced significantly after 6d of low temperature treatment, while biomass of steam reduced significantly after 12d treatment, but the percentage of epigeous biomass under different treatments changed not obviously. The final yield statistics indicate that Autumn Low Temperature has significant effect on grains, empty grains, and setting rate. Increased the low temperature treatment, the grains decreased, and the empty grains increased, those result in the reduction of setting rate. Different treatment yield of per plant were significant different, and the longer the treatment time, the lower the per plant yield.3. We took observation data of 78 weather stations from 1963 to 2012 in Jiangxi Province to statistic Autumn Low Temperature occurs, and then combined ARCGIS and wavelet analysis to study the spatial and temporal distribution of Autumn Low Temperature, and we also research risk index distribution of Autumn Low Temperature in Jiangxi. The results showed that the number of Autumn Low Temperature was more in the north than that in the south of Jiangxi. The average date of Autumn Low Temperature during 50a was Sept.21, and the earliest date was Sept.11, while the latest date was Oct.6. The primary period of mild Autumn Low Temperature was 10a, but the primary period of the moderate was 5a, the primary period of the severe was 8a. The severe risk religions of Autumn Low Temperature were located in the middle, in the northeast, and in the northwest of Jiangxi. And the moderate risk areas were located in the south of Jiangxi, such as Xingguo, Ningdu, Yudu, Ruijin, and so on. The others were moderate-risk areas.