| Chilling damage is one of the most serious meteorological disasters for crops in Northeast China, which happens very often and causes a lot of economic losses. In recent years, as the climate changing tends to be warmer and warmer, delayed chilling damage rarely happened in a wide range of area, but the regional and interim chilling damages occurred frequently. Obstacle chilling damage is getting worse since the abnormal climate change and fluctuation in temperature. Therefore, predict and protect the crops from low temperature during their growing season is important for the grain production in Northeast China. The main contents of this thesis are as follows:1. According to the features of the climate, analyzes the main meteorological factors (rain, radiation and accumulative temperature) closely related to the growth and development of crops of northeast China,and the frequency and area of chilling damage, proved that it is necessary to defense the chilling damage on this region.2. The various physiological indexes of different period under low temperature were analyzed. The results indicate that POD,proline and chlorophyll contents decrease in contrast to MDA content which increases during each growing stage. The changes in these four indices are significantly correlated with LTT (p<0.01). The D value of the four indices not only has a significant correlation with LTT,but also is higher than the result of each index. In conclusion, the D value can be used to effectively evaluate and classify the low temperature tolerance of rice.Using the weighted average of subordinate function values (D value) of those four physiological indices,the relative cold tolerance shown by each variety was determined.3. The rice grain empty rate of 6-14d continuous 9d of 7 main cultivated rice varieties in northeast China were determined through linear interpolation, and the relationship between the grain empty rate and days in low temperature were analyed by using regression method. The result indicated that all of the rice varieties in this test showed the highest grain empty rate when in low temperature for 10-13 days,then changed not significantly. Changbai19 which is more sensitive to low temperature is first reached highest empty grain rate. And according to the results, Jijing81 is the most insensitive variety to low temperature. The cold tolerance ability of the other 5 varieties was between the two varities.4. 7 main cultivars have been chosen as the material, which have been treated in low air temperature during heading, booting and filling stages. The relationship between low air temperature of different stage and rice quality has been analyzed. The results indicate that filling stage is the most important and has the biggest influence on rice quality, and then is the heading stage, booting stage has the lowest impact on rice quality. The results also tell us that different rice varieties have different tolerance to cold. The difference of three nutrients content of the same varieties in different growing season under low temperature has certain correlation with the cold tolerance. The reduction of three nutrients in the same growth period was no significant correlation.5. After being treated under low temperature during seedling stage, root activity of these 7 main rice varieties in northeast China were analyzed. The results indicated that under the low temperature range 8-12℃, root activity was inversely proportional to the number of days with treatment and showed a good linear relationship.The root activity difference among varieties is greater than among treatments, which proved that rice root activity is closely related with the characteristics of rice varieties.6. Summarizes the diagnosis indexes of corn chilling damage and set up a remote diagnosis and management system of corn chilling damage base on Web, preliminary application have been done,and get a good application effect.
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