Study On Tolerance Of Watermelon Under Low Light

Low light is the main restricting factors of watermelon’s normal growth and development. With different maturity and different ploidy’s watermelon as the materials, study on the change of photosynthetic characteristics of the material,and the morphological parameter, biochemical characters, fruit quality under low light stress. In order to select the appraisal index of watermelon of low light level and provide the theory basis for weak light resistance breeding.The results are as follows:1There are some differences between different materials at photosynthetic characteristics, parameter analysis on the photosynthetic characteristic of the fifteen materials showed:W6,W7,W13with strong ability of use the weak light, and W3,W4,W8,W14,W15better at dark respiration, W4,W6,W7,W8,W13,W15better at photosynthesis compared with other materials in a relatively weak light intensity.2Different variety of watermelon at seedling stage were treated in weak light with two functional leaves in the illumination incubator.The results showed:with the low light treatment leaf area and leaf dry weight both declined, specific leaf area increased, chlorophyll a declined, chlorophyll b and chlorophyll a/b both increased first and then declined. With the development of treatment days, the content of MDA,the activity of POD,CAT in different variety of watermelon all increased,the activity of SOD was different,some declined first and then increased,some increased first and then declined.3The influence of different varieties of watermelon under two levels of weak light intensities stress(30%and60%shading rate) were studied,the results showed:under the different treatments of low light level to different varieties of watermelon,the plant fresh weight and dry weight declined, the ratio of dry weight to fresh weight some increased and others declined, stem diameter become thinner, stem long become length, leaf area and leaf dry weight both declined, specific leaf area increased, total chlorophyll and chlorophyll a both declined, chlorophyll b and chlorophyll a/b both increased first and then declined.Under two levels of low light intensities stress the content of MDA, the activity of POD,CAT all increased,the activity of SOD was different, some declined first and then increased,some increased first and then declined, the yield and quality declined.4Comprehensive evaluation of the above indexes could determine that: W4,W7,W8,W9,W13with strong ability at the tolerance of low light, W3,W5,W6,W15shitty at the tolerance of low light,W11,W12growth better but have low fruit-bearing rate and W11both have no melon under the two two levels of low light intensities stress,the other breeds’ tolerance under low light are between the above breeds.5Parameter analysis on the photosynthetic characteristic of different could be more accurately understanding the materials watermelon’ photosynthetic,and rapidly make sure different varities’ tolerance under low light. The morphological parameter and physiological and biochemical indexes change consistent both in seedling stage and growing period. The results showed: morphological parameter like plant fresh weight, dry weight, stem diameter, stem long, leaf area, leaf dry weight, and physiological and biochemical indexes like total chlorophyll, chla, chlb, chla/b, the content of MDA, the activity of POD,CAT ratio as determinging indexes,more study needed on the tatio of dry weight to fresh weight and the activity of SOD.