Physiologic And Biochemical Of Perennial Ryegrass Response To Cadmium & Acid Soil Complex Stress And Release Effect Of Exogenous Melatonin

Pot experiments are carried out to study acid soil(p H7.0,H5.0,p H4.5,p H4.0,p H3.5,p H3.0)and cadmium(0mg/L,5mg/L,10mg/L,20mg/L,30mg/L,50mg/L,75mg/L,100mg/L)stress regularity about perennial ryegrass biomass accumulation,acid soil and cadmium combined stress(50mg/L Cd + p H4.0 acid soil,50mg/L Cd + p H3.0 acid soil,100mg/L Cd + p H4.0 acid soil,100mg/L Cd + p H3.0)effects on growth metabolism and nutrient absorption of perennial ryegrass and the regulatory effects of exogenous melatonin(100?mol/L,200?mol/L,300?mol/L)on perennial ryegrass under acid soil and cadmium combined stress.The results of this study are as follows:The results of single stress test of cadmium & acid soil show that the acid soil of p H5.0 and p H4.0 promote the growth of the perennial ryegrass,while the acid soil of p H3.5 and p H3.0 inhibit the growth of the perennial ryegrass.The growth inhibition of Perennial Ryegrass is most significant in the acid soil of p H3.0,and the biomass of the aboveground and underground part of the perennial ryegrass decreased by 5.13%and 7.31%,respectively,compared with that of p H7.0.The effect of Cd on the perennial ryegrass also has the same rule,when the concentration of Cd treatment is less than 30mg/L,the growth of the perennial ryegrass is promoted,but when the concentration of Cd is higher than 30mg/L,the growth of the perennial ryegrass is inhibited.The most inhibition of the growth of the perennial ryegrass with the concentration is100mg/L Cd.Compared with the 0mg/L Cd treatment,the biomass of the aboveground and underground parts of perennial ryegrass decreased by 48.97% and 51.33%,respectively.The results show that cadmium & acid soil combined stress treatment have significant effects on the growth and metabolism of perennial ryegrass.The stress degree of perennial ryegrass under 100mg/L Cd & acid soil stress treatment of ph3.0 is the highest.Compared with 100mg/l Cd treatment,the content of available Cd in soil increased by 48.15%,the content of Cd in aboveground and underground part of perennial ryegrass also increase by 10.97% and 20.34%,respectively.The inhibitory effect on the growth of aboveground and underground parts of perennial ryegrass is the highest,and the nutrient elements(K,Ca,Mg,N,P)in the body are significantly decreased.The content of Cd in perennial ryegrass increases,which aggravated the degree of oxidative stress.At the same time,cadmium & acid soil combined stress also inhibits the absorption of mineral nutrients of the roots of perennial ryegrass,and affects the growth and development of perennial ryegrass.Exogenous melatonin at different concentrations(100 ?mol/L,200 ?mol/L,300 ?mol/L)can effectively alleviate the injury of perennial ryegrass under cadmium & acid soil combined stress,and 200?mol/L melatonin have the most significant remission effect on perennial ryegrass.Compared with 100mg/L Cd &p H3.0 acid soil compound stress treatment,the Cd content in the aboveground part of perennial ryegrass decrease by 48.02%.The biomass,chlorophyll content and nutrients nutrient elements in the abovegrund part of perennial ryegrass is reduced by 48.02%,and the content of superoxide anion and malondialdehyde in perennial ryegrass are significantly decreased.The results show that melatonin could effectively hinder the transport of Cd from underground part to underground part in perennial ryegrass,and at the same time,it also can eliminate excessive reactive oxygen species in perennial ryegrass.Thus,the oxidative stress of Cd on perennial ryegrass is effectively alleviated.