Studies On High Temperature Tolerance Character And Selection Of High Temperature Tolerance Germplasm Is Cucumber (Cucumis Sativus L)

Cucumber (Cucumis sativus L.) is an important vegetable crop. Both in open field and in protection field it suffered from heat injury, which severely influenced the crop production. In this experiment, some cucumber cultivars of different ecotype were selected to study the changes of morphology, interior and physiological-biochemical under heat stress in seed germination, seedling and adult plant stages. The correlation of heat tolerance among different stages, and the appraised index and method of heat tolerance germplasm in early stages were studied and used as Jhe selecting program of heat tolerance germplasm. The main results are as fellow:The cucumber with heat treatment in seed germination performed the decrease of germination ability, and increase of MDA content, and decrease of SOD activity, and the growth inhibition of the cucumber radicle. The performance of cucumber in seedling stage are: the seedling fruitless growth and trend of fine roots, the reduction of chlorophyll a/b, and the destruction of the integration of chlorophyll and thyolokid membrane; The performance of cucumber in flower stage are: fruitless growth in the early stage, the early ageing in the late stage, the reduction of the yield, of the fruit rate, and of the Vc content, and the increase of deforming fruit rate and the drop of the fruit quality. The lethal time of most cucumber cultivars' leaf mainly change rated from 15 to 25 minutes.The correlation of the heat tolerance of the cucumbers existed among different growth stages. The appraised indexes in seed germination stage were determined as germination index at 42 癈, the radicle length rate of 38癈 for 60 hours, and MDA content of hypocotyls at 38癈. Both the lethal time of cucumber leaf and IL of cucumber leaf at 50 癈 in 1 5 minutes can be the appraised indexes at seedling stage in all cucumber cultivars. The absence and change rate of change point of IL can be used as important reference indexes of heat tolerance in seedling stage. The morphological change of chlorophyll and thyolokid in leaf under heat stress at 44 癈 can be used as appraised index of cytology. The significant correlation between yield change rate and the radicle length rate at 38癈 in 60 hours can be used as appraised index of cucumber heat tolerance in early stage. An equation was stimulated to estimate the heat tolerance in different cultivars.In this experiment, eight heat tolerance cucumber cultivars were selected: Yinxing, Japan cunlu, Japan jizao number3, Xiaqing number4, 631-1, 315, Jinyan number4, bailvjie. 631-1 showed high heat tolerance in all stages.Postgraduate: Meng LingboMajor: Olericulture Supervisor: Prof .Qin Zhiwei...