Response Characteristics To Cd Stress Of Salix Viminalis Seedling And Cutting Seedling

Salix viminalis is a Salix plant of Salicaceae,which is a potential tree species that can effectively accumulate heavy metal Cd.Studies have shown that different genotypes of Salix viminalis have great differences in the accumulation ability of heavy metals.Therefore,the breeding of Salix viminalis resistant varieties has important practical significance.At present,the breeding period of Salix viminalis resistance is long and the efficiency is low,and the research on the resistance of Salix viminalis is mainly based on cutting seedlings,and there are few studies starting from the seed germination stage.Therefore,in order to improve the efficiency of resistance screening of Salix viminalis,in this study,we analyzed the physiological changes of germination,seedlings and cuttings of Salix viminalis and the expression of genes related to Cd stress under Cd stress.The response characteristics of Salix viminalis seedlings and cuttings to Cd stress were investigated.The main findings are as follows:(1)By observing the seed germination index under Cd stress,we can see that the low concentration of Cd stress promoted the germination and seedling growth of Salix viminalis seeds to some extent;while the high concentration of Cd treatment significantly inhibited the wormwood seed germination and early seedling growth.Among them,the two indexes of the activity index and the root length were the most affected by stress,indicating that these two indicators can reflect the tolerance of plants to some extent.(2)The SOD activity and POD activity of Salix viminalis seedlings and cutting seedlings were significantly higher than that of the control at the initial stage of low concentration stress.There was a downward trend.Therefore,the antioxidant enzyme activities of seedlings and cuttings under Cd stress were consistent.(3)The proline changes in Salix viminalis seedlings and cuttings are consistent,but the soluble sugar content of Salix viminalis seedlings is lower than the control on the 20 th day,cutting seedlings on the 20 th day,it fell below the control,and the soluble sugar content in the seedlings did not increase significantly,indicating that the seedlings were more resistant than the cutting seedlings.(4)Under Cd stress,the content of malondialdehyde in the leaves of Salix viminalis seedlings and cuttings was higher than that of the control,and it increased first and then decreased with the number of stress days.The difference was that the total malondialdehyde content in the seedlings was the same.Below the cutting seedlings,it indicated that the seedlings had a lower degree of membrane lipid peroxidation and stronger resistance under Cd stress.(5)Among the genes related to Cd uptake and transport,Nramp3,Nramp6,ZIP1,were inhibited in leaves of Salix viminalis seedlings,and ZIP1 were up-regulated in cuttings.In the genes associated with Cd stress detoxification,MT2 B,PCS1 were significantly different from the control in the seedlings.PCS1,MT2 B,and Cu/Zn SOD showed significant changes in the cutting seedlings.In summary,The resistance of Salix viminalis seedlings to Cd stress was stronger than that of cutting seedlings.Principal component analysis shows that in the germination index,the vigor index and the root length inhibition rate can be used as key indicators for the early tolerance screening of Salix viminalis.Among the physiological and molecular indicators measured,antioxidant enzymes SOD,POD,osmotic regulator PRO,membrane lipid peroxidation product MDA,genes related to cadmium uptake and transport,Nramp3,Nramp6,ZIP1,and cadmium detoxification-related gene MT2 B,PCS1 can be used as an important index to evaluate the tolerance of heavy metals in Salix viminalis seedlings;antioxidant enzymes SOD,POD,osmotic adjustment substances PRO,SS,genes related to cadmium absorption and transport ZIP1,genes related to cadmium detoxification PCS1,MT2 B,Cu/ Zn SOD can be used as an important index to evaluate the heavy metal tolerance of Salix viminalis.The analysis of the above physiological indexes and gene expression provided a reference for the screening of key indicators of tolerance to heavy metals in Salix viminalis and the mechanism of resistance breeding of Salix viminalis.