Physiological And Biochemical Mechanism Of Silicon On Enhancing Yield And Quality Of Glycyrrhiza Uralensis Under Drought And Salt Stress

This paper studies the effect and mechanism of silicon(Si)on root yield,the content and accumulation of effective components of Glycyrrhiza uralensis(G.uralensis)through adding exogenous Si treatment under different drought and salt stresses by pot culture experiment,and analyzing and comparing the growth,physiological and biochemical characteristics,root yield,content and accumulation of active components by dynamic sampling for one year.It provides an important theoretical basis for the high root yield and high quality of cultivation G.uralensis.The main results are as follows:1.Si significantly promoted the shoot growth of G.uralensis under all stressed treatments at 70 days after treatment,but Si increased root growth of G.uralensis under all stressed treatments at 110 days after treatment.Si effectively alleviated the damage caused by drought and salt stresses on anatomical structure of the G.uralensis leaf,made some of the spongy cells palisaded,the cells structure was relatively complete,the arrangement became tight,and the vascular area increased slightly.2.The effect of Si on root yield of G.uralensis was significantly improved under drought and salt stresses.And the enhancement effect was more obvious under SD1,SD2.Si treatment increased the relative content and accumulation of various active ingredients in G.uralensis during the experiment.And the effect was the strongest under SD2 stress,followed by S stress.3.Si increased the antioxidant enzyme activities and non-enzymatic antioxidants content to alleviate the lipid peroxidation damage caused by drought and salt stresses,reduced ROS content,decreased the cell membrane permeability and MDA content.And this effect varies with the degrees of stress and growth periods.At 70 days after treatment,Si improved CAT,APX activities and AsA content under S stress;under SD1 stress,Si mainly improved the CAT,GPX and GR activities,and GSH content;Si improved the CAT,APX,GR activities and AsA,GSH content under SD2 stress.At 110 days after treatment,the effect of drought and salt stresses and the regulation of Si were more prominent.Under S stress,Si increased APX,GPX,CAT activities and AsA content,while decreased POD activity;under SD1 stress,Si mainly improved the antioxidant CAT,APX,GR activities and GSH content;under SD2 stress,Si increased APX,GPX,GR activities and GSH,AsA content.4.Si treatment significantly reduced Na+ content under all stressed conditions and increased K+ content in roots,stems and leaves of G.uralensis under certain stress,thus increased K+ / Na+ ratio at some extent.In addition,Si treatment significantly affects the contents of proline,soluble sugar and soluble protein at 110 days after treatment,and the osmotic adjustment was achieved by synergistic effect among each other.5.Si increased the activities of carbon metabolism enzyme of G.uralensis under salt and drought stresses during the experiment.And this effect was strongest under SD2 stress.While the total carbon content reached a significant level only at 70 d after treatment under SD1,SD2 stress.Si improved the NR activity at 70 d after treatment under SD2 and increased GS activity during the experiment,increased total nitrogen content under S and SD1 stress during the experiment,thus significant increased the C / N ratio under SD1 and SD2 stress during the experiment.6.Si improved chlorophyll content,RWC under stressed conditions,thereby enhanced the photosynthetic rate;transpiration rate,stomatal conductance and intercellular CO2 concentration significantly increased,and ultimately improved water use efficiency under SD1 and SD2 stress,and then improved the tolerance of G.uralensis to drought and salt stresses.7.The possible mechanism of Si regulated root yield and quality of G.uralensis under different degrees of drought and salt stresses may as follows: On the one hand,Si could alleviate the oxidative stress,osmotic pressure,enhance carbon and nitrogen metabolism,improve photosynthesis and water use,thus improve their resistance,and further improve the growth,and improve root yield of G.uralensis.On the other hand,Si could improve organic osmolytes content and carbon and nitrogen metabolites content,thereby affect the content of effective components in G.uralensis.However,the increase of active ingredients accumulation is achieved by both the promotion of root yield and secondary metabolites content.