Physiological And Biochemical Response Of Ophiopogon Perennial Ryegrass To Aluminum Stress And Mitigative Effects Of Exogenous Magnesium Treatment

A pot experiment was conducted to explore the effects of varity concentrations?0,5,25,50,100 mg/kg?Al,and the regulatory pathway of?0.2,0.4,0.8 and 2 mmol/L?of exogenous Mg under Al treatment on the growth of Perennial ryegrass.The experimental results showed that:?1?The results showed that low-dose Al treatment?<25 mg/kg?nearly has no effect on plant growth.On the other hand,high-dose Al??25 mg/kg?significantly inhibited the growth of ryegrass plants.Moreover,with the increase of Al dose,chlorophyll contents and root activity showed a trend of decrease,same with that of N,P,K,Ca,Mg,content in plant tissues?shoots and roots?except for the root P content).With the increase of Al doses,the Al,Zn and Mn accumulation of root and shoot all gradually increased?root>shoot?.In addition,the content of malondialdehyde?MDA?,superoxide anion?O₂·^-?and the activities of peroxidase?POD?also increased with increasing Al doses,while the activity of catalase?CAT?and superoxide dismutase?SOD?showed a trend of decrease followed by increase.These results suggested that higher dose of Al??25 mg/kg?poisoned ryegrass plants may through accelerating the absorption of root Al,Zn and Mn ions,improving malondialdehyde?MDA?and O₂·^-content,decreasing antioxidant enzymes?CAT and SOD?,root activity,and reduced N,P,K,Ca,Mg accumulation.?2?Al accumulated to a greater degree in roots than in shoots and resulted in oxidative stress,as evidenced by increased concentrations of hydrogen peroxide and malondialdehyde.In addition,Al exposure markedly hindered root and shoot elongation and biomass production,decreased the content of chlorophyll and root activity,reduced the activities of H⁺-ATPase,Mg²⁺-ATPase and Ca²⁺-ATPase in the plasma membranes?PMs?,and inhibited the absorption of mineral nutrition.However,the addition of various Mg doses alleviated the inhibitory effects on plant growth caused by Al,elevated the activity of the PM H⁺-ATPase,Mg²⁺-ATPase and Ca²⁺-ATPase in both shoots and roots,and partially enhanced the uptake of minerals?N,P,K,Ca,Mg,Cu and Fe?in Al-treated plants.Shoot and root Al,Mn,Zn accumulation significantly diminished when plants were subjected to Al plus Mg treatments.Moreover,the addition of Mg considerably upregulated catalases?CAT?and superoxide dismutase?SOD?activity in shoots under Al stress.The results obtained in this work indicate that Mg applied exogenously,particularly at millimolar?0.4M,0.8M or 2M?doses,can effectively deplete the detrimental effects on perennial ryegrass growth,likely by reducing oxidative damage,modulating mineral absorption,improving root activity and re-establishing the levels of ATPases.