Alleviation And Physiological Mechanism Of Hydrogen Sulfide In Cadmium Stress Of Phlox Paniculata L.

Cadmium(Cd)pollution seriously harms the environment and human health.Excessive cadmium in soil is easy to be absorbed and accumulated by plants,which affects plant growth,cell division and metabolic activities.Hydrogen sulfide(H2S)is a small molecule gas.Recent studies have found that H2S is related to the response process of plant hormones and other signal molecules,which can not only regulate the growth and development of plants,but also improve the ability of plants to resist abiotic stress.This study Phlox exam(Phlox Paniculata L.)as the experimental material,through the seed germination experiment and pot experiment,to explore the injury to plants under cadmium stress and damage the physiological mechanism of H2S to alleviate stress,groping under Cd stress appropriate concentrations of H2S to improve plant stress resistance,further for phytoremediation of cadmium pollution to provide certain theoretical basis.1.Seed germination test results were obtained by soaking 0(CKH2s),0.3,0.6,0.9 and 1.2 mM sodium sulfide hydride(NaHS,H2S donor)in CdC12 solution with concentrations of 0(CKCd),100,200 and 300 M,respectively.Results are as follows:(1)Cd stress can significantly reduce the blessing from the seed germination rate,and NaHS with relief,of which 300 mu M CdCl2 under duress,0.9 mM NaHS treatment group compared with CKH2s,seed germination rate increased by 225%.(2)Cd of radicle growth also has obvious inhibitory effect,under 200 mu M CdC12 stress,65%lower than in control CKcd radicle length,and length of radicle after 0.6 mM NaHS treatment increased by 27%.Under 300 M Cd severe stress,NaHS had no obvious effect.(3)Cd stress also significantly reduced the length of the germ,while NaHS did not significantly promote the growth of the germ,but inhibited its growth.2.The 2-year old Phlox plants were potted in the soil containing 0,0.3,0.6 and 1.2 mg/kg CdC12,and then the leaves were sprayed with NaHS(0,0.3,0.6,0.9 and 1.2 mM).Results are as follows:(1)As the increase of CdC12 concentration,plant height,leaf length,leaf width and stem thickness all showed a decreasing trend when H2S was not sprayed.However,the decreasing trend could be slowed down by spraying H2S,and the overall effect of 0.6mm NaHS treatment was obvious.Further studies have shown that H2S can reduce the Cd transport coefficient of Phlox,suggesting that H2S can alleviate the inhibition of Cd on plant growth by reducing the accumulation of Cd in leaves.(2)The production rate of MDA,superoxide anion radical and the leakage rate of relative electrolyte all showed an upward trend with the increase of cadmium stress concentration.The determination results of antioxidant enzymes showed that external application of H2S can improve the activity of APX,POD,CAT and SOD,indicating that H2S can resist the harm of reactive oxygen species generated by Cd stress on plants by increasing the activity of antioxidant enzymes.(3)Cd stress can reduce Photo,Cond and Tr.0.6 M H2S under Cd stress can increase Photo by 33%,82%and 30%,respectively.Chlorophyll fluorescence parameters of determination results showed that when the blessing by Cd stress test,PSII actual photochemical efficiency(?PS II)?and electron transfer efficiency(ETR)is reduced,which both had different degree after spraying hydrogen sulfide,suggested that H2S can improve the activity of PSII linear electron transfer,increase efficiency and increase the net photosynthetic rate and reduce the heat dissipation(NPQ).(4)H2S sprayed can reduce the rise of ABA under stress.Combined with the results of Cond,it is speculated that hydrogen sulfide can reduce the influence of the transition decline of stomatal conductance caused by ABA accumulation under cadmium stress on photosynthesis.Based on the above experimental results,factor analysis method was used to calculate and evaluate the damage status of plants.This study also established a prediction model for H2S to increase plant resistance and reduce soil cadmium pollution,aiming to provide reference data for H2S to improve plant resistance and enhance environmental remediation capacity.