The Physiological And Biochemical Response Of Perennial Ryegrass To Cadmium Stress And The Regulation Effect Of Exogenous Calcium Treatment

In order to understand the mechanism of calcium?Ca?regulation of cadmium?Cd?stress on the seedling and mature stage in the perennial ryegrass?Lolium perenne L.?,we carried out the following two experiments.The seedling stage experiment was conducted in the liquid medium with the following 6 treatments:CK?0 mg/L?,5 mg/L,25 mg/L,50 mg/L,75 mg/L,100 mg/L Cd²⁺in the mature phase,the experiment was carried out in a pot experiment with sand as substrates,the treatments are as the follows:CK,160mg/kgCa²⁺,75mg/kgCd²⁺,75mg/kgCd²⁺+160mg/kgCa²⁺,75mg/kgCd²⁺+160mg/kgCa²⁺+0.4mmol/L EGTA.The main results of the experiment are as follows:?1?With the increase of the stress concentration of Cd,the growth of the root length of perennial ryegrass gradually decreased,the poisoning rate increased,the germination rate and germination potential of the seedlings decreased.Comparing with the Cd treatments,application of 160 mg/LCa²⁺significantly increased the length of root and shoot,and the seedling biomass,greatly decreased the relative leaf conductivity and malondialdehyde?MDA?content,incremented the activity of the superoxide dismutase?SOD?and peroxidase?POD?.Application of Ca²⁺maybe presumably improve the seedling growth under Cd stress through reducing cell damage.?2?The application of exogenous Ca greatly alleviated the injury symptoms caused by Cd stress.Comparing with the Cd stress,the application of Ca greatly increased the biomass of root and shoot,chlorophyll content and net photosynthetic rate;and significantly reduced MDA content and leaf relative conductance,the production rate of hydrogen peroxide?H₂O₂?and superoxide anion?O₂^-?;increased the content of free proline and soluble sugar;accelerated the activity of SOD,POD,catalase?CAT?,ascorbic acid peroxidase?APX?activity,and the content of glutathione?GSH?;increased the effective Ca content in plants;improved the transfer ability of ryegrass to Cd,transfer Cd to the inactive region of cell metabolism and reduce the toxicity of Cd.EGTA and Ca exert less effect than Ca alone,and even inhibit it.This indicated that the external Ca can enhance the photosynthetic capacity of perennial ryegrass,inhibit ROS accumulation,enhance the antioxidant defense system,reduce the mobility of Cd,and alleviate its symptoms.