Effects Of Exogenous Melatonin On Growth And Physiological Characteristics Of Chinese Cabbage Seedlings Under Temperature Stress

Chinese cabbage is a biennial Brassica plant of Cruciferae.It has good taste and high nutritional value,and is deeply loved by Chinese people.The yield of Chinese cabbage is mainly affected by high temperature or low temperature stress.However,there are few reports on the response of Chinese cabbage to low temperature stress.Previous studies have found that melatonin can improve the stress tolerance of many plants,but there are few reports on Chinese cabbage.Melatonin is a small molecule substance with high activity.Studies have found that it can also enhance the tolerance of plants to low temperature.Using ’Jiangguan’and ’Jingyan’ Chinese cabbage varieties as experimental materials,this study studied the effects of exogenous spraying melatonin on the growth and development of Chinese Cabbage Seedlings under normal temperature,low temperature stress and high temperature stress,mainly including physiological indexes such as root length,leaf length,plant height,photosynthesis,reactive oxygen species metabolism,malondialdehyde and soluble protein.Through the development of this study,we will clarify whether the physiological role of melatonin（MT）in plant stress resistance can be applied in Chinese cabbage,provide protective measures for the impact of different temperature stress on Chinese cabbage yield,and hope to provide relevant theoretical basis for the wide application of melatonin in different plants.The main results of this study are as follows:（1）The appropriate concentration of MT soaking treatment can effectively alleviate the inhibition of high temperature stress on Chinese cabbage seed germination,but the high concentration of MT soaking treatment can inhibit the germination of seeds.（2）MT pretreatment can effectively alleviate the inhibitory effect of high temperature stress on the growth of Chinese cabbage seedlings.In this test,the effect of MT treatment with 100 μ M concentration is the best.（3）MT pretreatment increased the activities of SOD,pod and cat of Chinese cabbage seedlings,so as to improve the ability of seedlings to resist high temperature stress.（4）MT pretreatment can effectively alleviate the inhibitory effect of low temperature stress on the growth of Chinese cabbage seedlings.In this test,the effect of MT treatment with 100 μ M concentration is the best.（5）MT pretreatment increased the activities of SOD,pod and cat of Chinese cabbage seedlings,so as to improve the ability of seedlings to resist low temperature stress.