Physiological Mechanism Of Pear Plant Response To Cd Stress Mediated By Passivator Applied

Soil is an important resource for human survival.In addition to natural factors,heavy metal pollutants can enter the soil through human activities,such as mining and industrial wastewater,causing soil heavy metal pollution.Heavy metal ions will enter the body along with plants absorbing water and nutrients from the soil,and finally enter the human body through the transmission of the food chain to damage human health.Nowadays,soil heavy metal pollution has become one of the global problems that threaten food safety and human health.Sorbus seedlings were planted with a cultivation substrate mixed with 100 mg·kg^-1 heavy metal cadmium powder and 4%passivating agent（bentonite,biochar,quicklime,calcium superphosphate and their combinations）by soil volume,and the effective soil cadmium content,basic soil physicochemical data,plant biomass,photosynthetic fluorescence parameters and active oxygen content were measured after 70 d of treatment to investigate the effect of adding different passivating agent treatments on soil heavy metal The physiological response of pear seedlings to Cd stress was investigated.The results of the study showed that.2.The addition of passivators significantly reduced the effective Cd content in the soil,and the combination of two passivators was more effective than single passivator treatment.2%bentonite with 2%biochar resulted in the largest decrease in the effective Cd content in the soil,with a 66.1%reduction compared to the control.Bentonite,biochar and calcium superphosphate improved soil organic matter and fast-acting nutrient content,with biochar increasing soil organic matter content the most,by 48.50%compared to the control,and calcium superphosphate increasing soil fast-acting phosphorus content the most,by 76.03%compared to the control.Lime enhanced soil fast-acting nutrient content,but soil organic matter decreased by 5.93%compared to the control after addition.In this study,we investigated 32 pear orchards in Liaoning,analyzed the heavy metal contamination in pear orchard soil,and selected potted sorbus（Pyrus ussuriensis maxim.）seedlings as the test material for the experiment,3.The addition of passivation significantly slowed down the damage of cadmium stress on sorbus seedlings,and the MDA and reactive oxygen content in all tissues of the plants were significantly lower than that of the control,and the MDA content in all tissues of the plants decreased most significantly after the addition of 2%bentonite and 2%biochar,with 28.84%,18.95%,and 12.89%decrease in roots,stems,and leaves,respectively,compared with the control.The content of antioxidant enzymes in all tissues of the plants was also significantly lower after addition of passivation than the control,and the expression of antioxidant enzyme genes in all tissues of the plants was down-regulated.The indices of biomass,root vigor,and root mitochondrial function of the passivator treatment compared to the control plants were greatly increased.The addition of 2%bentonite with 2%biochar and 2%calcium superphosphate with 2%biochar increased the root vigor of the plants most significantly,both nearly doubled compared to the control.The photosynthetic parameters of the plant leaves were significantly increased by the addition of passivation agents,in which the net photosynthetic rate of the leaves increased by 77.26%with the addition of 2%bentonite and 2%biochar compared to the control treatment.The analysis of the physicochemical data in this study showed that the addition of 2%bentonite plus 2%biochar had the best effect on the passivation of heavy metal Cd in soil,which could improve the soil environment and promote plant growth,and was a better combination of passivating agent to mitigate soil Cd pollution.