Study On The Adaptability Of Ecological Environment And Low Light Stress Of Hybrid Rice

The experiment was carried out from 2006 to 2009 year, in quite different conditions of the four ecological sites. The altitude is approximately 530m,550m, 1055m and 1500m. During the critical period in the growth and reproductive growth of hybrid rice, there are significant differences of temperature, light and precipitation. In this paper, we conducted some studies on the adaptability and mechanism of hybrid rice such as morphological changes, function and metabolism, hormone levels and the differences of protein expression, matter production and yield. The study consisted of three parts, the first part was the ecological adaptability of hybrid rice. In 2006, we comparative studied on the ecological adaptability of the 18 hybrid rice varieties in Wenjiang, Hanyuan and Xichang. Meanwhile, we conducted a comprehensive evaluation and screened some varieties which had differences on the comprehensive adaptive capacity and ability to adapt to light for the next year trial. The second part was the shading test at initial stage of panicle emerging of hybrid rice varieties in two different types of ecological conditions. In 2007, we studied the adaptability and adaptation mechanism in the two types of ecological prerequisites of 6 hybrid rice varieties under low light stress at Wenjiang and Hanyuan. The third part was the shading test about different types seedling rice, in 2009, Yaan, the farm of Sichuan Agricultural University. Based on the study in 2007, we investigated the adaptability and adaptation mechanism of 4 hybrid rice varieties which had different types. The main results were following.1. In the different ecological conditions, there were significantly differences in leaf area and flag leaf area of hybrid rice full heading stage, hybrid rice had a strong ability for regulating leaf area; there were significantly differences in chlorophyll content, ratio of chlorophyll a/b, carotenoid content and photosynthetic rate of hybrid rice, hybrid rice varieties could form an excellent photosynthetic performance in Hanyuan ecological site; hybrid rice could reduce some physiological hanges such as synthesizing chlorophyll and carotenoid, reducing chlorophyll a/b ratio for increasing the capacity of ecological adaptation, especially it could increase the adaptability about glare and low light. Because of different light stimuli in different ecological environments, hybrid rice could start to adapt in different ways. In the different ecological conditions, there were significantly differences in dry matter accumulation, output rate of stem and sheath, yield components and yield of hybrid rice, the factors which had greater impact on yield were dry weight per plant, seed setting rate and thousand-grain weight. The 15 indicators of principal component analysis showed that the indexes which had larger contribution on ecological adaptability of hybrid rice were photosynthetic rate, relative conductivity, flag area, leaf area per plant, dry weight per plant, effective panicle, chlorophyll content, photo-oxidation rate, carotenoid content, grain yield and output rate, these phenomena showed that we should focus on improving photosynthetic performance and enhancing resistance of hybrid rice for increasing production in the test environment.2. The photosynthetic rate, conductivity, thousand-grain weight dry matter weight, photo-oxidation rate, output rate of different hybrid rice was different distinctly. Different varieties of hybrid rice might have a common way of ecological adaptation, also might have their own different special way of ecological adaptation. such as the common way:changing the leaf area of hybrid rice, the special way: increasing the chlorophyll, chlorophyll b and carotenoid content, reducing photo-oxidation rate, decreasing the material output of leaf and enhance stress resistance. The 18 varieties of hybrid rice was divided into wide suitable varieties, pervasive varieties, especially suitable varieties using comprehensive evaluation method of principal component analysis. The varieties of ecological adaptability strongly were Yifeng8, Hongyou2009, Dyou7511, Jinyou188, Chuanjiangyou3, Cyou725, Xianyou63,â…¡you363, Gangyou725 and Xieyou9308.3. Hybrid rice showed the same result by shading (about 85%) in initial heading stage in two ecological sites. Hybrid rice could resist the effects of low light on photosynthesis and maintain the relative stability of photosynthetic rate by adding more chlorophyll content and chlorophyll a/b ratio. Chlorophyll photo-oxidation rate tended to increase by shading, shading was promoting the chlorophyll synthetic rather than stopping the decomposition to increase the chlorophyll content, especially chlorophyll b. Shading on rice could increase the angle of flag leaf and reduce the fresh weight of upper 3 leaves significantly, but had no significant effect on trilobites and leaf area. Shading on hybrid rice could change its distribution rule of organic matter, although increase transformation rate and export rate of the matter in stem-sheath, but reduce the leaf decomposition of organic material, which lead to reduction of the seed-setting percentage and thousand-grain weight significantly and production was greatly reduced, and it showed that Photosynthetic capability after initial heading stage of hybrid rice was important to yield formation. Overall, the effect of shading on the morphological characteristics, characteristics of photosynthetic characteristics, resistant, material production and transport distribution yield and its formation factors of different varieties of resistance were different. In low light, Wide adaptability varieties of yifeng8 and hongyou2009, low light resistance varieties of beifeng3 and gangyou527 could keep stable of the photosynthetic characteristics, bio-membrane structure, SOD activity, material production and distribution characteristics and the ability of yield formation, they could even start against mechanism of low light, such as changing the flag leaf Angle, enhancing SOD activity, increasing the chlorophyll b content, reducing the organic material output and even dramatically reducing production to maintain normal physiological function and leaves growth. Low light intolerance varieties of gangyou527 could not keep stable.4. The different degree of shading (about 67% and 86%) on hybrid rice in seeding period could significantly influenced tiller number of different varieties of Low light resistance. Tiller number tended to reduce significantly along with the increase of low light stress. The result shows that proper degree of shading on hybrid rice in seeding period could increase the plant height and the leaf area, but excessive degree of shading could significantly decrease the plant height and the leaf area of low light resistance. The high degree of shading is good for improving the content of soluble sugar and the ratio of C and N on the strong varieties of low light resistance. The degree of shading is good for improving the chlorophyll a, b and content of chlorophyll on the strong varieties of low light resistance, the content of chlorophyll b more than chlorophyll a, the ratio of chlorophyll a and chlorophyll b decreased. The shading treatment is good for improving the content of ABA, ZT and GA in nursery period, the result shows that different degree of effecting on different varieties. The shading treatment could produce new protein spectral bands on 33 kD position of hybrid rice, the protein spectral bands e (26-33kD) expressed the strongest variety is 3 number of Bei-Feng on the strong varieties of low light resistance. The result shows that increasing degree of shading can improve the active of SOD on the strong varieties of low light resistance.5. The author according to the test results combine with other research results suggested that:Ecological adaptability evaluation should consider the adaptability of survival and the adaptability of production; Evaluation index should choose important indexes or exclude intercommunity and instantaneous of physiological indexes; Comprehensive evaluation should use suitable the method of statistical analysis for all indexes of test result of years.