The Research Of Appraisal Method And Index Of Low Temperature And Weak Light Resistance In Watermelon

12different genotypes of watermelon seedings were studied in low temperature stresstreatment, and selected three different cold tolerant watermelon materials. The coldtolerance of3watermelon materials seeds during the germination were analyzed with fivedifferent temperature, study of low temperature, weak light resistance in watermelonseedings and the change of growth characteristic, photosynthesis and physiological andbiochemical characteristics under low temperature or/and weak light, to develop anefficient,comprehensive appraisal index and evaluation method for cold-resistance, weaklight-resistance watermelon, the purpose of this study was to provide theoretical basis forthe actual production breeding for low temperature, weak light watermelon germplasmresources.1.12different varieties of watermelon seedlings as materials, at10℃, light100μmol.m-2.s-1, watermelon chilling injury index statistics, preliminary screening of coldresistance materials. The results show that the chilling injury index of each genotype wasdifferent under different processing time. it is concluded that each type of cold resistancestrength through the determination of chilling injury index in6, and8days treatment, andchoose ‘hong ye yi hao’ as cold tolerant germplasm, moderately cold resistance varietiesgerplasm ‘kang bing su mi’and cold sensitive germplasm ‘chen lan’, and the three varietieswere tested at low temperature and weak light treatment.2. Under different temperature conditions, the differences between three varieties ofseeds germinating capacity. Under the condition of25℃, three varieties of initialgermination, germination rate and length of radicle were higher than other processingconditions; Under the condition of10℃,5℃, three varieties of seeds germination werenot. Under25℃to15℃processing, red wild relative germination rate, relative radiclelong lower number one slowly. Especially under the condition of15℃, disease-resistantSu Mi and orange orchid sprouts slow, respectively to5days,6genius germination, andgermination rate is extremely low, radicle growth.3. Under low temperature stress treatment after7days, the growth of watermelonsignificantly suppressed, plant height, stem diameter, leaf area, plant fresh dry weight, rootfresh dry weight were reduced by different degrees, the lower processing temperature, thegreater the decline, and clear difference between each type. Watermelon photosynthesis isaffected by low temperature stress is obvious, after low temperature stress, the leaf netphotosynthetic rate, stomatal conductance and transpiration rate, ratio of Fv/Fm, the qP arelower, intercellular CO2concentration; Disease-resistant Su Mi, orange orchid of chlorophyll a and chlorophyll b, total chlorophyll a/b ratio, chlorophyll, red wild one lowerchlorophyll a, chlorophyll a/b ratio, chlorophyll b, total chlorophyll increased. As thetemperature lower SOD activity, POD, APX enzyme lowered after the first trend overall,MDA content increased4. As the processing of light is abate, watermelon seedlings increased plant height,growth of other indicators and reduce; The photosynthesis inhibition, show the netphotosynthetic rate, transpiration rate, stomatal conductance, qP, decrease in the totalchlorophyll content; Intercellular CO2concentration, Fv/Fm ratio increases; Under theweak light three varieties have different seedling leaf of SOD increased trend, in the100μmol.m-2.s-1light intensity under each type are rising,30μmol.m-2.s-1condition, the redwild SOD enzyme activity than number one contrast decreases, disease-resistant Su Mistill increase, orange rose less than100μmol.m-2.s-1under the condition of the increase.Activity of POD, APX enzyme activity and MDA content increase gradually with theillumination weakened.5. Weak light in low temperature processing, in addition to the red wild1in15℃,and100μmol.m-2.s-1increase plant height, the other processing conditions, and othervarieties showed a trend of lower, stem diameter, leaf area, plant fresh weight, plant dryweight, root fresh weight, root dry weight were significantly reduced; Weak light in lowtemperature results in the decrease of Pn, Gs, Tr, qP, Ci to rise. Under the condition of thesame low temperature processing, Fv/Fm ratio increases with light weakened. SODenzyme activity under low temperature and weak light intercross stress overall trends tofall-litres, POD are greatly influenced by temperature, with lower temperature, PODenzyme activity at first and lowered later but still greater than the control. APX enzymeactivity increased, MDA content increase sharply.