Effect Of Brassinolide On Physiological Characteristics Of Leymus Chinensis (Trin) Under Salt Stress And High Temperature Stress

Leymus chinensis(Trin)is a kind of grassy perennial plant,which is one of the important pastures of grassland meadow.L.chinensis not only has the characteristics of delicious herbaceous,high protein content and high grass content,but also plays an important role in preventing soil erosion and improving grassland ecological environment.With the destruction of the ecological environment,the growth of L.chinensis is now seriously threatened.Brassinolide(BR)is a new type of plant growth regulator,which not only can effectively promote the normal growth and development,but also alleviate the damage caused by stress on physiological and biochemical characteristics of plant.Pot experiment was conducted to assess whether exogenously applied BR at various concentrations could alleviate the adverse effects of salt stress and high temperature stress on L.chinensis and to clarify the mechanism of physiological function which will provide the theoretical basis and technical reference for exogenous BR application.The main results are as follows:1.Effects of different concentrations of BR on growth and development of L.chinensis under salt stressThe effects of different concentrations(0.01 mg / L,0.1mg / L,1mg / L)of BR on the growth and development of L.chinensis were studied.The results revealed that salt stress(Na Cl concentrations is 150nmol/L)substantially disrupted the growth and development of L.chinensis.And the experimental results also showed that spraying the appropriate concentration of BR treatment,help to alleviate the salt stress on the growth and development of L.chinensis.In the treatment of three different concentrations,0.1 mg / L BR treatment had the best effect for increasing the plant height,leaf area,root/shoot ratio,chlorophyll b,carotenoids,soluble protein content,dry and fresh weight and the malondialdehyde(MDA)content was the lowest;0.01 mg/ L BR treatment had the best effect on increasing total chlorophyll,chlorophyll a contents,root activity and proline content.In terms of the activity of five antioxidants,the highest activity of superoxide dismutase(SOD)and glutathione reductase(GR)was found with 0.01 mg / L BR treatment,the highest activity of ascorbate peroxidase(APX)and peroxidase(POD)was found with BR concentration 1 mg / L treatment,and the highest activity of catalase(CAT)was found with BR concentration of 0.1mg /L treatment.In general,the optimal concentration of BR treatment was 0.01~0.1 mg/L under salt stress.2.Effects of different concentrations of BR on growth and development of L.chinensis under high temperatureThe effects of different concentrations(0.01 mg / L,0.1mg / L,1mg / L)of BR on the growth and development of L.chinensis were studied y exogenous spraying under high temperature stress.The results showed that exogenous spraying BR could increase the plant height,leaf length,leaf width,fresh weight,photosynthetic pigment,proline,soluble substance and antioxidant enzyme activity,and reduce the amount of MDA.BR concentration of 1mg/L treatment significantly increased the plant height and accumulation of dry matter of L.chinensis.BR concentration of 0.1mg / L treatment could gain the largest root vitality.The experimental results revealed that high temperature stress substantially perturbed the growth,photosynthetic pigments and root activity of L.chinensis,however,the deleterious effects of high temperature were partially ameliorated by the application of BR.The chlorophyll a,carotenoid,total chlorophyll content,chlorophyll a / b value,proline content and GR activity were the highest when treated with 1 mg / L BR.When the concentration of BR was 0.1 mg/ L,the leaf width,dry and fresh weight,chlorophyll b,soluble sugar and protein,root activity and SOD,CAT and APX activities were the largest and MDA content were the smallest.When the concentration of BR was 0.01 mg / L,the plant height,leaf area,leaf length and POD activity were the highest.In general,when the BR concentration of 0.1mg / L and 1mg / L treatments were used,there were significantly promoting the growth and development and biomass of L.Chinensis and when the BR concentration of 0.1 mg / L was the most effective remedy for L.chinensis under high temperature stress.