Research On Cold Resistance Of Mangrove Seedlings Kandelia Obovata In High Latitudes Based On Artificial Intervention

Mangrove plants are thermophilic plants,and temperature has always been the main factor limiting mangrove development to the north.At present,the northernmost boundary of artificial introduction is Yueqing,Zhejiang?28°N?.Kandelia obovata is the most cold-resistant mangrove species in China today.The research team has developed a series of domestication techniques for mangrove K.obovata to the north and successfully moved it to Zhoushan,Zhejiang?29.9°N?,In this study,the K.obovata seedlings introduced from the north are used as test objects.The cold tolerance of the Kandelia seedlings is studied through manual interventions such as artificial introduction,setting of a rheological domestication system,and addition of external nutrients.We use the means of manual intervention as independent variables,POD,SOD,CAT,MDA,chlorophyll,volatile substances,total phenol,ASA,proline and other antioxidant-related indicators as dependent variables.The main research contents and results of this article are as follows:1.K.obovata seedlings grown in different places from the same source showed different adaptability.Under natural low temperature stress,K.obovata seedlings introduced artificially to Zhoushan grow slowly,when subjected to natural cold stress.The chlorophyll's contents exhibit the decrease tendency and 2-butanol and 2,3-butanediol are firstly found in K.obovata after being moved to Zhoushan.The SOD and CAT activity of half-wilted K.obovata leaves from Zhoushan increase significantly,and their POD activity decrease.And SOD could convert oxygen radicals to hydrogen peroxide,and then CAT and POD could work together to remove hydrogen peroxide.The study provides a foundation for mangroves response to natural low temperature in high latitude.2.Under the domestication of a mobile and convenient system,winter K.obovata seedlings grow slowly,lower than the other three seasons,but maintains a normal physiological state as a whole.By increasing the temperature during part of the time,the system enables the plant body to produce sufficient nutrients to cope with low temperature stress,so that the MDA level of winter K.obovata seedlings remains normal.The content of chlorophyll and phenols also reached the highest value in the four seasons in summer.Antioxidant enzyme system regulates stress when the plant body is under stress,so that the plant body maintains a healthy state,and the enzyme activity shows a certain correlation with temperature.3.Under low temperature stress,exogenous proline regulates changes in antioxidant enzyme activity and stable proline production,therefore,the anti-oxidation ability of the K.obovata seedlings can be maintained,and the cell membranes and the like can be prevented from being oxidized by free radicals,so that the mangrove seedlings can adapt to the low temperature environment.It can be seen that exogenous proline plays an important role in the plant's antioxidant defense system under low temperature stress.In addition,it is important to strictly control and balance the production and elimination of ROS at the intracellular level.Otherwise,cellular components and damage caused by ROS will affect the overall growth,metabolism,development and overall productivity of mangrove.Under low temperature stress,exogenous application of porphyrin magnesium complex did not significantly improve the antioxidant system of K.obovata seedlings to cope with stress,on the contrary,it will make the K.obovata seedlings overreact.Therefore,it is proposed that when photosynthesis exceeds the limit of the plant body itself,the electron transfer system is oversaturated to generate excess electrons,which is transferred to O₂ to produce O₂^-and other active oxygen,which leads to a sustained increase in the content of MDA.Under low temperature stress,the application of exogenous glucose can alleviate the antioxidative system of K.obovata seedlings in response to low temperature stress.Before20 d,the MDA content of the experimental group to which exogenous glucose was applied was relatively stable and lower than that of the control group.The purpose of exogenous glucose application is to ensure that the K.obovata seedlings under cold stress have sufficient carbon source nutrients.Therefore,exogenous application of glucose to the plant body of K.obovata seedlings can alleviate the effects of low temperature stress.