Study On Exogenous Betaine To Improve Drought Resistance Of Phoebe Hunanensis

Biennial seedlings of Phoebe hunanensis Hand.-Mazz(P.hunanensis),which was used as the research object,were applied different degrees of water stress,and different concentration exogenous betaine solution was respectively sprayed to the leaves of P.hunanensis to improve the drought resistance.Through the determination of multiple physiological and biochemical indexes of leaves,the effects of different concentrations of betaine solution on the basic physiological effects,osmotic adjustment system and antioxidant system of P.hunanensis under different water stress conditions were investigated.The research of drought resistance of P.hunanensis could provide a theoretical basis for improving the drought resistance of P.hunanensis,and it is of great practical significance for the large-scale planting and promotion of Phoebe plants to the north of the Yangtze River.In this experiment,the leaves of P.hunanensis were respectively applied four different degrees of water stress(0m L,400 m L,800 m L,1200 m L)every three days,and at the same time,four different concentration exogenous betaine solution(0mmol/L,50mmol/L,100mmol/L,200mmol/L)was sprayed,the relative water content,electrical conductivity,malondialdehyde content,free proline content,soluble protein content,soluble sugar content,superoxide dismutase activity,catalase activity and peroxidase activity of the leaves of P.hunanensis were regularly measured through dynamic sampling method,and the results are as follows:(1)Under the drought stress condition,the relative water content of leaves of P.hunanensis was significantly reduced.Relative water content of leaves of P.hunanensis was effectively increased by spraying betaine solution,and the effect increases as the increase of betaine concentration.And the concentration of 100mmol/L of betaine solution treatment had the best effect.The relative water content of the leaves could also be maintained by betaine solution under adequate irrigation conditions,but it was not determined by its concentration.(2)Under drought stress conditions,the electrical conductivity of P.hunanensis leaves was significantly increased,and also of the malondialdehyde content.The treatment of the suitable concentration of betaine solution effectively alleviated the improvement of cell membrane permeability in this environment and inhibited the accumulation of membrane lipid peroxidation products.Under long-term sufficient irrigation conditions,the treatment of betaine could also increase the electrical conductivity of P.hunanensis leaves,and it was positively correlated with the concentration of betaine solution.The malondialdehyde content of leaves was significantly increased by the high concentration treatment of betaine solution.(3)Under drought stress conditions,the proline content,soluble protein content and soluble sugar content of leaves of P.hunanensis were increased with the prolongation of stress time,while betaine solution could further promote proline content and soluble protein content and they are positive correlated.High concentration of betaine solution can also promote the accumulation of soluble sugar content,and the promotion effect of low and medium concentration betaine solution is not well than that of high concentration.Under sufficient irrigation conditions,the treatment of betaine had no effect on the content of proline and soluble sugar in leaves of P.hunanensis,while the content of soluble sugar was positively correlated with the concentration of betaine.(4)Under the condition of drought stress,the activity of SOD and CAT enzymes in leaves of P.hunanensis were both increased,and the activity could be further increased by spraying betaine solution.The activity was positively correlated with the concentration of betaine solution,in which the activity was the best when the betaine solution concentration is 100mmol/L.Under the sufficient irrigation conditions,the activities of antioxidant enzymes(SOD,CAT,POD)in leaves of P.hunanensis gradually achieved at the same level with the prolongation of time.(5)The physiological and biochemical indexes of P.hunanensis showed a certain dose effect on exogenous betaine,and was also related to the degree of water stress.When the concentration of betaine was equal to or lower than 100mmol/L,the changes of physiological and biochemical indexes were positively correlated with the increase of GB concentration,but when the concentration was higher than 100mmol/L,the variation of these physiological indexes were not further increased but will lead to some inhibition or weakening of this activity,which is not conducive to the normal growth of P.hunanensis under this condition.However,under sufficient irrigation conditions,low concentration of betaine solution did not affect the normal growth of P.hunanensis,but high concentration would inhibit it.