Effects Of High Temperature And Waterlogging Stress On Growth And Development Of Non-heading Chinese Cabbage

Non-heading Chinese cabbage(Brassica campestris L.ssp.chinensis Makino)is also called pakchoi,small Chinese cabbage.It is a kind of green leafy vegetable native to China,that likes cold climate,which is sensitive to high temperature especially extreme high temperature,growing well at 18 to 20℃ temperature,but when the temperature is higher than 25℃,its growth potential is abate,and its quality to drop.It is often harmed by high temperature and waterlogging stress,when cultivated in summer and autumn resulting in low yield,poor quality and even death.Because there are some differences in the tolerance to high temperature and waterlogging among different varieties,it is particularly important to breed good varieties having strong ability to survive.In this paper,there are two non-heading Chinese cabbage varieties,W1 and W2,with different tolerance to waterlogging and high temperature,to be used as research materials in order to study the impact on its growth,dietary fiber content and the cellulose synthesis of related enzymes under the stress of high temperature and waterlogging.The main research results are as follows:1.Under high temperature stress,plant height,root-crown ratio,plant fresh and dry weight,leaf area,leaf water content of the two non-heading Chinese cabbage varieties W1 and W2 were all decreased,which had a greater decrease to above growth indexes as the stress temperature increased.And the decrease of their growth indexes were even more under both high temperature and waterlogging stress,althouth that showed the same trend as that single high temperature stress.Meanwhile,the variety W1 with resistance to high temperature and waterlogging had a stronger growth ability of the main growth index than the variety W2,which had poor resistance to high temperature and waterlogging,at the same high temperature stress and high temperature waterlogging stress.2.Under high temperature stress,there were a trend of increased first and then decreased among the content of cellulose,hemicellulose and lignin,but that had a decreased trend to the soluble pectin in two non-heading Chinese cabbage varieties W1 and W2,and the change range of these dietary fiber content became more big as the temperature increased.There were additive characteristics that the effect of stress both high temperature and waterlogging on the dietary fiber content in two non-heading Chinese cabbage varieties W1 and W2,and the effect were more big to the dietary fiber content as the stress temperature increased,leading to be harder to recover after stress was removed.In addition,the variety W1 with a resistance to high temperature and waterlogging,that had a bigger increase to the content of cellulose,hemicellulose and lignin,but a smaller decrease to the content of soluble pectin when compared with the variety W2 with a poor resistance to high temperature and waterlogging under the same stress of high temperature and waterlogging.3.Under high temperature stress,there were a trend of increased first and then decreased to the activities of the CesA,SS and KORRIGAN enzymes in two non-heading Chinese cabbage varieties W1 and W2,while CE enzyme activities showed an opposite trend.And that there were a greater change trend as the stress temperature increased.Under the stress of high temperature and waterlogging,the change trend of these enzymes activities were also similar to that single high temperature stress,but which had a greater effect than that single high temperature stress.Moreover,the activities of CesA,SS,KORRIGAN enzymes in variety W1 with a resistance to high temperature and waterlogging,that had a bigger increased,but smaller decreased than the variety W2 having a poor resistance to high temperature and waterlogging.And the CE enzyme activity of variety W1 increased less but decreased more than variety W2,under the same high temperature and waterlogging stress.