Study On Chelating Agents And Plant Growth Regulator Strengthening Tall Fescue To Repair Heavy Metal Contaminated Soil

Cadmium is the most polluted heavy metal in China’s soil,which is difficult to degrade under natural conditions and poses a threat to the ecological environment and human health.Tall fescue has good tolerance to heavy metal cadmium and is an ideal phytoremediation material.Abscisic acid（ABA）can improve stress tolerance in plants,but the application of natural type ABA in agricultural practice is limited due to its chemical instability,rapid catabolism and high production cost.8′-alkynyl abscisic acid[8′-（C₂H）ABA],a functional analogue of ABA,has similar application effects to natural ABA and has higher activity than ABA.At present,there are few studies on the application of 8′-（C₂H）ABA in heavy metal contaminated soils.In this thesis,we compared the concentration and application methods of exogenous8′-（C₂H）ABA,a plant growth regulator,and biodegradable chelators,tetrasodium glutamate diacetate（GLDA）and ethylenediamine disuccinate（EDDS）,to investigate the effects of 90 mg/kg cadmium treatment on physiological,biochemical and photosynthetic characteristics of tall fescue,as well as the effects on cadmium uptake,translocation and enrichment in tall fescue,to investigate the effects of exogenous8′-（C₂H）ABA and biodegradable chelating agents were applied in combination as follows:（1）90 mg/kg Cd had a significant inhibitory effect on the biomass of tall fescue,increased reactive oxygen species（ROS）caused oxidative damage,promoted membrane lipid peroxidation,and decreased chlorophyll content affected its photosynthetic capacity.exogenous 8′-（C₂H）ABA significantly improved the growth of tall fescue under Cd stress,enhanced the tolerance of tall fescue to Cd,improved its uptake and translocation enrichment capacity of Cd,and reduced the toxic effects of Cd on The protective effect of exogenous 8′-（C₂H）ABA on photosynthetic system of tall fescue under Cd stress was demonstrated by chlorophyll fluorescence induction kinetic curve.Combined with the physiological index data,20 mg/L exogenous8′-（C₂H）ABA had the best effect on enhancing the stress resistance and cadmium transport enrichment of tall fescue.（2）At a Cd stress of 90 mg/kg,the bioeffective state of Cd could be increased by adding the biodegradable chelating agent GLDA or EDDS to the soil in stages,which also alleviated the toxic effects on plants due to excessive levels of chelating agent applied at one time,promoted the growth of tall fescue,and enhanced the uptake and transport enrichment of Cd.Among the treatment groups,9 mmo/L GLDA had the best effect on the activation of cadmium form.Among the EDDS treatment groups,treatment with 6 mmol/L EDDS had the best effect on biomass and cadmium uptake and translocation enrichment of tall fescue;among the GLDA treatment groups,the 9mmo/L GLDA treatment group had the best effect on biomass and cadmium uptake and translocation enrichment of tall fescue,which was better than the 6 mmol/L EDDS treatment group.（3）The combination of exogenous 8′-（C₂H）ABA and biodegradable chelator GLDA or EDDS applied to tall fescue under 90 mg/kg Cd stress significantly increased its biomass and also enhanced its Cd translocation and enrichment capacity.The combination of biomass and Cd translocation and enrichment of tall fescue showed that the combination of 20 mg/L 8′-（C₂H）ABA+9 mmo/L GLDA treatment group was the most effective.In terms of biomass,the root and aboveground biomass of the 20 mg/L 8′-（C₂H）ABA+9 mmo/L GLDA treatment group was 1.85 times and1.07 times higher than that of the Cd treatment group without 8′-（C₂H）ABA with chelator,respectively;compared with the Cd treatment group,the translocation coefficient and extraction rate of tall fescue were increased by 1.37 times and Compared with the Cd treatment group,the transport coefficient and extraction rate of tall fescue increased by 1.37 times and 12.97 times,and the enrichment coefficients of roots and aboveground increased by 2.32 times and 7.05 times,respectively.（4）The results of this study showed that the efficiency of Cd-contaminated soil remediation by tall fescue under 90 mg/kg Cd contamination could be improved by foliar spraying of 20 mg/L exogenous 8′-（C₂H）ABA combined with the application of 9 mmol/L GLDA to the soil.