| Cucumber(Cucumis sativus L.) is a thermophilic vegetable, and can't grow normally under high temperature. Heat stress is the main restrict factor that inhibits the growth of cucumber in summer. In this experiment, we studied the physiological characteristics of cucumber under heat stress, the inheritance of heat resistance and the affects of exogenous substances on heat resistance with four different heat-resistant cucumber inbred lines and their first generations as the test materials. The main results were as follows:1 The activities of SOD, POD and CAT, contents of praline and MDA increased significantly under heat stress. This indicated that the seedlings were injured under high temperature and a positive response was induced to reduce the heat damage. The reactions of four materials on heat stress were different. The activities of SOD, POD and CAT increased rapidly in inbred lines No.2 (heat-resistance), and decreased 3 days later,but maintained high level, which showed that the inbred lines had the high ability to scavenge the active oxygen. The proline content increased significantly under heat stress, which was good to the maintenance of cell osmotic potential and to reduce heat injury. This can be seen from the lower elecctrolytic leakage and lower MDA content under heat stress. The activities of SOD, POD and CAT increased rapidly in inbred lines No.3 (heat-sensitive), however, the rate is lower than inbred lines No.2, and decreased 2 days later. The protective enzymes activities were significantly lower than the heat-resistant materials under heat stress, showed that had lower ability to adapt to high temperature, and was seriously injured under heat stress.2 Whether parents were heat sensitive or heat resistance materials, the activities of SOD, POD and CAT in the F1 generation were increased under heat stress, and showed better performance than its parents. The performances to heat stress of F1 generations were different with different parent materials. The Hybrid generation had high protective enzyme activities under high temperature stress when its parents were heat-resistant materials, had mid protective enzyme activities (tend to the heat-resistance) when parents were heat resistance and heat-sensitive materials, and had lower protective enzyme activities when the parents were heat-sensitive materials.The proline content of F1 generation of heat-resistant materials increased under heat stress.The F1 generations had a lower relative conductivity and MDA content when its parents were heat-resistant materials and heat-sensitive material, which indicated that the adaptability of cucumber to heat stress could be increased by use of hybrid. Heat-resistant offspring of two parents heat capacity; heat and thermal hybrid parents, their offspring heat resistance and heat resistance similar to the parents; two hybrid thermal material, the heat capacity of weak offspring, so in the process of cross breeding, we must ensure that future generations of the heat capacity, at least one of the parents ability to heat.3. The protective enzyme activities of cucumber seedlings under 50μmol·L-1, 100μmol·L-1, 200μmol·L-1 SA treatments were significantly higher than CK, and the best performance was observed under 100μmol·L-1SA treatment. After 3 days of heat stress, the activities of SOD, POD and CAT of cucumber seedlings under 5 mmol·L-1, 10 mmol·L-1and 15mmol·L-1 of CaCl2 treatments were significantly higher than CK, and the best performance was found under 10 mmol·L-1 CaCl2 treatment.4. Under heat stress, protective enzymes activities, proline content of cucumber seedlings treated with 100μmol·L-1SA and 10mmol·L-1 CaCl2 were significantly higher than CK, whereas relative conductivity and MDA content were significantly lower. This indicated that the heat-resistance of cucumber seedlings was increased by the compound treatment. However, the performance of cucumber seedlings under the compound treatment was worse than under single treatments of 100μmol·L-1SA and 10 mmol·L-1 CaCl2. which indicated that there were antagonism existed between SA and CaCl2.
|
PDF Full Text Request