| Leymus chinensis is widely distributed in the grassland of China.It is a kind of perennial grass with high productivity,nutritional value and palatability,and plays a major role in conserving soil and water resources and supporting livestock production.Now facing serious degeneration and various biotic and abiotic stresses,it is urgent to restore grassland productivity through effective measures.This paper focuses on the effect of brassinolide(BR)on seedling growth of L.chinensis under low temperature stress and shading,and tries to clarify the mechanism of physiological function.It is expected to provide a method to restore degradation of grassland productivity,and provide a theoretical basis for the artificial cultivation of grass.The main results are as follows: 1.Effect of brassinolide on growth and physiological characteristics of L.chinensisunder low temperature stress This experiment was conducted to study the effects of exogenously applied different concentration of BR on the growth and physiological characteristics of L.chinensis seedlings under low temperature.The results indicated that foliar application of BR could improve plant height,leaf area,increase plant fresh weight,dry weight,chlorophyll a and chlorophyll b,total chlorophyll,carotenoid contents and chlorophyll a/b ratio,at the same time,further increase the contents of proline,soluble sugar and protein,antioxidant enzyme activity,and reduce the accumulation of MDA.The suitable concentration of BR treatment was 0.1mg/L.BR could improve the biosynthesis of photosynthetic pigments,regulating the contents of osmotic adjustment substances and antioxidant enzyme activity,reducing the accumulation of MDA.In this way it is possible to promote the growth of L.chinensis under low temperature stress.2.Effect of brassinolide on photosynthesis and chlorophyll fluorescence traits of L.chinensis under varying levels of shade This experiment was conducted to study the effects of BR on the photosynthetic efficiency and chlorophyll fluorescence and growth of L.chinensis under different light conditions: control(100% natural light),light shading(70% natural light),moderate shading(50% natural light).The result showed that shading significantly increased the growth,photosynthetic pigment synthesis,photosynthetic rate and improved chlorophyll fluorescence characteristics of L.chinensis as compared to control.The order of increase was mild shade>moderate shade>natural light except chlorophyll where the order of increase was moderate shade>mild shade>natural light.Also,the application of BR further increased the plant height,fresh weight,dry weight,chlorophyll and carotenoid content and characteristics of gas exchange and chlorophyll fluorescence characteristics.In the experiment conditions,the results showed that appropriate shading significantly promote plant growth through alterations in physiological attributes of L.chinensis,while,application of BR further improves the plant growth through enhances photosynthetic efficiency.3.Effects of brassinolide on antioxidant characteristic and endogenous hormones of L.chinensis in different illumination strength The effects of BR on the endogenous levels of hormones,lipid peroxidation,osmolytes and antioxidants characteristics of L.chinensis under control(100% natural light),light shading(70% natural light)and moderate shading(50% natural light)by pot experiments were studied.The results showed that as compared with control,shading increased the contents of abscisic acid(ABA),zeatin riboside(ZR),gibberellin(GA)and indole-3-acetic acid(IAA);at the same time,reduced osmolytes accumulation(soluble sugar,protein,free amino acid and proline),lowered antioxidant enzymes such as peroxidase(POD),superoxide dismutase(SOD)and catalase(CAT)activities.But the application of BR improved the osmolytes accumulation and antioxidant enzyme activity of plant;reduced the content of malondialdehyde(MDA)and relative conductivity.The application of BR increased the contents of ABA,ZR,GA levels,and decreased IAA level.It needs to further research the regulation mechanism of BR on antioxidant characteristics,osmolytes accumulation and endogenous hormones of L.chinensis in different illumination strength. |
PDF Full Text Request