Effects Of Low Light Stess On Physiological Characteristics Of Hybrid Rice At Booting Stage And Flowering Stage

The experiment was carried out in 2007 and 2008 years, in Rice Research Institute of Sichuan Agricultural University. In 2007, six hybrid rice combinations (Eryou162, Neixiangyou 31, Beifeng 2,Yifeng 8, Hongyou 2009 and Gangyou527) with different photosensitivity were studied. And in 2008, selected Gangyou527 and Neixiangyou31 as test material which with different photosynthetic efficiency in hybrid rice. And processing shading treatment at booting and flowering stage respectively, analysis and determination their growth and development, physiological and biochemical indexs. Some of the characteristics of growth and development, the photosynthetic productivity, physiological and biochemical characteristics, production performance of rice under low light stress were studied, hoping to an in-depth analysis of the relationship between hybrid rice agronomic-traits, the physiological and biochemical indexs and output under low-light conditions, and research the difference of the response to low-light stress in differences type of rice, screening the characteristics of species to adapt to low light stress, provide theoretical basis for breeding low-light-resistant rice varieties and high photosynthetic efficiency breeding. The results showed as follows:1. After shading treatment at booting and flowering stage, low-light stress leading to plant leaf area per plant, plant height increased, but transport rate of the dry matter transfer to grain became very slowly, an increased the output which transfer to leaves, in order to maintain survive under the low light environment. On the whole, shading during the late growth stage had little effect on the rice morphological index, but had a significant impact on the final yield.2. Low-light stress seriously affected the rice production capacity of photosynthesis. After shading treatment, whether at booting stage or the flowering stage, the net photosynthetic rate of the flag leaf decreased, and the longer treatment time, the greater the drop rate, and high light efficiency varieties significantly better than low light efficiency varieties. Shading at booting stage and flowering stage respectively, chlorophyll content (SPAD), chlorophyll a, chlorophyll b, carotenoids and chlorophyll a / b were all effected, and a rising trend during the booting stage, first increased then dcreased at flowering stage, which may be related to its failure, but it can be seen on the whole, after shading chlorophyll b and chlorophyll content increased, chlorophyll a and chlorophyll b ratio decreased. The flag leaf area and leaf chlorophyll content of each shading treatment even at booting stage or flowering stage all were higher than the control. The two species were more obvious at booting stage, and the variety of low photosynthetic efficiency varieties (Neixiangyou 31) was affected seriously. SOD activity at booting and flowering stage were all single peak curve, the peak all appeared in the shadeing times, this showed that all of the two stage were light-sensitive period. The POD activity and MDA content in the whole growth period variation trends are similar, was rose slowly, SOD play the major protective effect in recovery period after low light stess, and POD play protection effect in the period under low-light. About the two rice combinations, Gangyou 527 had more talents to the light intensity variation. Proline and soluble sugar content all increased under low-light conditions.3. The output of different combinations under low light stress had different decrease ways, and the filled grains and seed setting rate's decline was the major factor. Poor light was less affected of lOOO-grain weight and grains per spike. The stress resistance of hybrid rice combination was directly related to the yield under low light stress. Further tests showed that shading at booting stage and flowering stage made the yield has a significant reduction, and it was impacted greatly at heading stage. Shading on the late growth stage has an important impact on the grain plumpness. In the two periods, dry matter accumulation of each treatment after shading less than the control, especially at the heading to the mature stage was the most obvious.4. The relative indexes after shading were correlation analysis at booting and heading stage, the relative value of ever indexes all had correlation in different degrees, some of them had achieved significant or very significant level. At the same time, due to the difference shade-tolerant mechanism between different varieties, every indexes of rice at the late growth stage had difference on the adaptation of low-light stress.