Study On Mechanism Of Winter Wheat Genotypes With High NUE And WUE In Using Water And Nitrogen Effectively

Arid and semiarid areas are main areas of food production in our country. Water shortage and nutrient deficiency are two key factors that restricted crop production in these areas. It is an important one in rational utilizing resources, decreasing environmental pollution and reducing inputs that exploiting plant descendible characteristics and potential of water and nutrients use, cultivating or utilizing genotype with high water and nutrition use efficiency, among these methods and approaches. Lots of studies on the screening of genotypes with higher NUE and WUE have been reported , but little have been done to understand the physiological mechanism in which winter wheat genotypes can use water and nitrogen efficiently. The objective of this study is to identify the physiological mechanism and to offer the theoretic basis for promoting and cultivating genotype with high water and nutrition use efficiency. Two experiments were carried out to discuss the difference of the physiological mechanism of different genotypes by using growth analysis and physiological testing method from the viewpoint of the metabolism, the regulation of dry matter & nitrogen accumulation & translocation and root characteristics et al with two genotypes(After having been studying for past several years, the genotype(Xiaoyan 22) with high effect high response and the genotype(Xiaoyan6) with low effect low response were screened from 10 local dominating winter wheat varieties.) under local environment. The main results are as follows:1. The grain yield of Xiaoyan 22 is significant higher than xiaoyan6 whether nitrogen applied or not. Nitrogen application contrasts to no nitrogen application, the grain yield increase rate of Xiaoyan22 and Xiaoyan6 was 33.4% and 28% respectively. The results of yield components showed that the yield of Xiaoyan6 mainly dependent on effective spikes, otherwise 1000-grain weight and the number of spikes contribute to that of Xiaoyan 22.2. The WUEGY and the WUEBY of Xiaoyan22 are higher than that of Xiaoyan6, whether nitrogen applied or not. The WUEGY of Xiaoyan22(24%) & Xiaoyan6(16.13%) and the WUEBY of Xiaoyan22(12.75%) & Xiaoyan6 (17.02%) were both increased under nitrogen application. The results showed that the WUEGY of Xiaoyan22 was enhanced by nitrogen application, but the WUEBY of Xiaoyan 6 was increased by nitrogen application.3. The results that the values of each nitrogen effective use characteristics of Xiaoyan22 are higher than that of Xiaoyan6 showed that nitrogen application not only increase the nitrogen effective use and nitrogen distribution, but also contributed to the yield increase of Xiaoyan22. The positive correlation between nitrogen flow efficiency and nitrogen absorption efficiency indicated that the total nitrogen accumulation in plant offers a good material foundation for the increase of nitrogen flow efficiency. The positive correlation between nitrogen absorption efficiency and nitrogen harvest index & nitrogen use efficiency showed that Xiaoyan22 is a genotype with high nitrogen absorption efficiency and high nitrogen use efficiency simultaneously.4. Studied on the physiological mechanism in which water is used effectively found that the leaf potential of Xiaoyan22 was lower than that of xiaoyan6, the leaf potential of Xiaoyan22 decreased significantly than that of xiaoyan6 under nitrogen applied. Xiaoyan22 is a high water use efficiency genotype with low leaf potential and low evapotranspiration according to the analysis of correlation.5. The leaf chlorophyll content and photosynthetic rate of Xiaoyan22 was significantly higher than that of Xiaoyan6 at both jointing stage and filling stage under nitrogen applied and no nitrogen applied. Filling stage is a key period for the contribution of grain yield, and the high Chlorophyll content layed a good physiological foundation for nitrogen effective use of Xiaoyan22. The nitrate reductase(NR) of Xiaoyan22 was significantly higher than that of Xiaoyan6 under nitrogen applied and no nitrogen application, especially at filling stage which should be a key period for judging the nitrogen metabolism difference of different genotypes with different leaf nitrate reductase(NR).6. The nitrogen remobilization quantity of Xiaoyan22 and Xiaoyan6 were 99.71 kg/hm2 and 92.71 kg/hm2 respectively. The nitrogen contribution to grain of Xiaoyan22 and Xiaoyan6 were 69.83 kg/hm2 and 72.88 kg/hm2 respectively, the nitrogen assimilation after-anthesis of Xiaoyan22 and Xiaoyan6 were 42.21 kg/hm2 and 34.54 kg/hm2 respectively showed that Xiaoyan22 has not only the high ability of nitrogen remobilization but also that of nitrogen absorption and nitrogen assimilation.