The Cold Tolerance And Screening Of Cold Tolerance Identification Indexes In Rice Varieties During Different Stages

Twenty-one rice varieties were provided by Rice Research Institute of Sichuan Agricultural University and its collaborated unit. Used the ways of normal temperature and low temperature, the morphological, growth and development indexes of cold tolerance were tested and analyzed during bud stage, seeding stage, booting stage, flowering and filling stages, got the cold tolerance in different stages, and researched the effects of low temperature at seeding stage on the express of the cold tolerance of rice at flowering stage. Using the relative magnitudes of representative varieties which had different cold tolerance, the morphological changes of plants, physiological functions and biochemistry characteristics, and their relations with cold tolerance were studied. Based on the correlation analysis and principal components analysis, got some screening of cold tolerance identification indexes. The following six sections concluded the core points of this study.1. Plant growth was inhibited under temperature stress. During bud stage and seeding stage, Livability was inhibited; at bud stage , the leaf number, root number and root length were not significantly correlated with livability. And the plant height, root number and root length also were not significantly correlated with livability in seeding stage under artificial low temperature; Under natural low temperature stress at seeding stage, leaf age ,length of the first length form the top, plant height and dry weight were inhibited. Through correlation analysis, except dry weight , they were significantly correlated with livability.2. The rice leaf, dry matter weight and filling character were effected after low temperature stress. Under low temperature stress in booting, flowering and filling stages, leaf area was less than its under natural temperature expect one variety. To same variety, the earlier low temperature was more than the latter in leaf seniling. At dry matter weight, the weight under low temperature was lighter than its under natural temperature, and the decline rate at filling stage was bigger than its at booting and flowering stages, but were not significantly correlated with their cold tolerance. After low temperature stress, the seed setting rare of three stages were decreased, and the number of secondary branches significantly decreased, while other indexes were not remarkable..3. There were conspicuous changes on physiological in plants under low temperature stress. At seeding stage, chlorophyll content and SOD activity decreased, while soluble protein, soluble sugar, praline, amino acid content and MDA content increased. In booting, flowering and filling stages, photosynthetic rate, transpiration rate decreased, soluble protein, soluble sugar, praline, amino acid and MDA content, SOD and POD activities increased. Through correlation analysis, soluble protein, praline and MDA content were significantly correlated with their cold tolerance in seeding stage. Photosynthetic rate and SOD activity were significantly correlated with their cold tolerance in flowering stage, while the indexes were not significantly correlated in booting and filling stage.4. Form this study, the cold tolerance of the rice was positive correlate in different stages. And the cold tolerance during seeding and bud stage, during booting and filling stage were significantly correlated.5. After low temperature stress in seeding stage , the seed setting rate was lower than natural temperature when ripened. Many seed setting rates under low temperature stress in seeding and flowering stages were lower than when only one stage under flowering stage low temperature stress. After low temperature stress at seeding stage, it could improve the cold tolerance when rice met low temperature at flowering stage.6. Using the results of correlation analysis, the indexes of 5 rice varieties in seeding and flowering stages were used to construct an equation by principle components analysis and line regression analysis and the equation was significant. Screened leaf age and MDA content identification indexes of cold tolerance in seeding stage, photosynthetic rate and SOD activity were screened in flowering stage.