Effect Of High Temperature And Waterlogging On Agronomic And Physiological Traits In Flowering Chinese Cabbage

Flowering Chinese cabbage is one of the main vegetable crops in South China and is planted throughout the year.However,in the summer and autumn high temperature seasons,the area is often accompanied by higher rainfall,and causes high temperature with waterlogging stress,which seriously affects the normal growth and development of flowering Chinese cabbage,resulting in a decline in yield and quality.At present,studies for the effects of high temperature stress on the growth and physiological characteristics of flowering Chinese cabbage have several reports,but there are few reports in studies for the effects of high temperature with waterlogging on the growth and physiological characteristics of flowering Chinese cabbage.In this study,4 flowering Chinese cabbage cultivars were selected as the research materials,some agronomic traits?such as plant height,plant weight,stalk height and stalk weight?and several physiological traits?such as SPAD value,some enzyme activities related to removing active oxygen species,a protective substance betaine,and an oxidative product malondialdehyde?MDA??were determined among 4 varieties under control and high temperature with waterlogging stress,the effects of the growth and physiological traits were analyzed under stress conditions,and several gronomic and physiological traits related to stress resistance were identified.These traits could be considered as indexes for evaluating the resistance capability of heat with waterlogging stress in flowering Chinese cabbage.The main results of the research are as follows:1.The effect of high temperature and waterlogging stress on agronomic traits in flowering Chinese cabbageThe capability tolerant to high temperature with waterlogging stress for the varieties tested was preliminarily confirmed.The effect of high temperature with waterlogging stress on the yield trait—stalk weight was measured in 4 varieties tested,it was found that the stalk weight decreased with different degrees for 4 varieties under heat with waterlogging stress,but the decline for“Sijiu-19 caixin”variety was smaller and non-significant compared with the control;while the stalk weight for the other three varieties“3T6”,“Youlu 50”and“Liuye 50”was significantly decreased in comparison with that under control condition.Therefore,“Sijiu-19 caixin”was preliminarily determined to be higher resistance to high temperature with waterlogging stress,and the other three varieties are those with weak resistance to high temperature and waterlogging stress.The effects of high temperature and waterlogging stress on some agronomic traits were analyzed in 4 flowering Chinese cabbage varieties.In comparison with control,the plant weight for four varieties was reduced,but the reduction amount of“Sijiu-19 caixin”was significantly lower than that of the other three varieties,which was basically consistent with the performance of stalk weight.The maximum canopy spread,maximum leaf length,maximum leaf width and maximum leaf petiole length in four varieties decreased in various degrees under high temperature with waterlogging stress,and the order of their sizes was basically the same as plant weight,“Sijiu-19 caixin”was the largest,followed by“Youlu 50”,“3T6”and“Liuye 50”.Among the above-mentioned traits,the differences among“Youlu 50”,“Liuye 50”and“3T6”were basically not significant,but the traits of three varieties were quite different from“Sijiu-19 caixin”.However,under high temperature with waterlogging stress,the plant height and stalk diameter had no significant difference compared with the control in the 4 cultivars tested,indicating that high temperature with waterlogging had little effect on the stalk diameter and plant height.Correlation analysis showed that the stalk weight had a very significant positive correlation with plant weight,and significant positive correlation with maximum canopy spread,maximum leaf length,maximum leaf width and maximum petiole length.These results indicated that stalk weight and plant weight could be considered as important indexes for evaluation the resistance to high temperature with waterlogging stress in flowering Chinese cabbage,and the maximum canopy spread,maximum leaf length,maximum leaf width and maximum petiole length could be considered as secondary indexes.2.The effect of high temperature with waterlogging stress on some physiological traits in flowering Chinese cabbageThe SPAD values of 4 varieties decreased with stress time under high temperature with waterlogging stress,but the reduced amounts in stress-sensitive varieties“3T6”,“Youlu 50”and“Liuye 50”were obviously more than that in stress-resistant variety“Sijiu-19 caixin”.In addition,the MDA contents in 4 varieties were increased under high temperature with waterlogging stress,indicated the degree of membrane-lipid peroxidation increased in all cultivars under the stress,but the increasement in the stress-tolerant variety“Sijiu-19 caixin”was much lower than that in the other three varieties.These results indicated that the reduction amount of SPAD value and MDA content could be considered as physiological indicators in flowering Chinese cabbage to evaluate its capability tolerant to heat with waterlogging stress.Under short-term high temperature with waterlogging stress,catalase?CAT?activity increased sharply in 4 cultivars;the other traits such as betaine content,O₂^-production rate,H₂O₂content,and activities of superoxide dismutase?SOD?and peroxidase Oxidase?POD?increased slightly.No significant difference was observed for the values of these traits in four varieties.With stress time,except for SOD enzyme activity,the other traits varied under stress in 4 varieties.The stress-tolerant variety“Sijiu-19 caixin”had higher betaine content,higher POD and CAT enzyme activities in comparison with stress-sensitive varieties,while the O₂^-production rate and H₂O₂content were lower than those in stress-sensitive varieties under high temperature with waterlogging stress.Therefore,these physiological traits could be considered as reference indexes for evaluating the capability of resistance to high temperature with waterlogging stress.