Research On Technique Of Hot Tolerance Identification By Morphology In Cucumber

Cucumber is a widely cultivated vegetable and deeply loved by people. The rising global temperature has brought serious influence to the production of cucumber. Cucumbers with different heat tolerance were used to determine the change of main morphological indexes in different stage of cucumber under artificial simulation and summer heat. Than through analyzing the variance and correlation of cucumber conclude the identification indexes of heat tolerance. The main results are as follows:1. Four cucumber cultivars with different heat tolerance were used to determine the change of main morphological indexes of cucumber under different temperature (35℃,38℃,42℃) condition while taking 25℃as the control (CK). The results indicated that the whole-plant fresh weight (X₁), fresh weight without cotyledon (X₂), shoot fresh weight (X₃), hypocotyl length (X₄), vigor index (X₅) showed a significant correlation with the heat-tolerance, which were suggested as the reliable screening indexes to identify heat tolerance of cucumber. The equation Y=-0.3473+0.2450X₂+0.0735X₅ can be used to forecast heat tolerance of cucumber by taking the simple indexes fresh weight (X₂) and vigor index (X₅) under the condition of 38℃stress at seed germination stage.2. Taken 4 different heat tolerance cucumbers as test martial. The same method was taken in seedling stage of cucumber. The results indicated that the seedlings grew excessively while the growth of roots was constrained, and the leaves turned yellow under short-turn heat stress. Plant height(X₁), shoot fresh weight(X₄), leaf area(X₃), leaf fresh weight(X₅), chlorophyll content(X₈) showed a significant correlation with the heat-resistant under 38℃, which could be identification indexes of heat tolerance of cucumber. The evaluating equation of Y=-2.6628+1.0686X₁+1.8367X₅ was got by stepwise regress. After testing it could be used to evaluate heat tolerance of cucumber.3. Conducting step high temperature treatment to detached leaves of 4 cucumber cultivars. The cell damage rates were measured by electrical conductivity method. Through A Logistic equation, the high semi-lethal temperature of A-1, A-2, B-1,B-3 was 45.18℃, 42.36℃, 48.93℃, 52.79℃, respectively.4. Taken 6 cucumber cultivars with different heat tolerance as test materials, determining the vegetative and reproductive growth, downy mildew status under natural in adult stage. The results showed that shoot height, stem height, leaf area, node number of plant, first fruit, female flower of main stem and aborted gourd were suggested as the reliable screening indexes to identify heat tolerance of cucumber in adult stage. Downy mildew could be used as the reference of heat tolerance identification.5. According to statistical analysis of identification indexes of cucumber in different stage, the identification methods of sprout and seedling stage could be taken as early identified technique.