Study On Tolerance,Enrichment And Transport Of Iris Ensata Under Zinc And Nickel Stress

With the development of society,a large number of heavy metal pollutants enter the soil,resulting in increased soil heavy metal pollution.Excessive heavy metal pollution will destroy the growth of plants,causing adverse effects on plants,and then affect the ornamental effect of garden plants.Iris ensata is a commonly used garden flower in Heilongjiang urban green space and has high application value.Therefore,this study takes I.ensata as the research material,and uses common heavy metal pollution zinc（Zn）and nickel（Ni）as pollutants.The single and combined stress of zinc and nickel was applied to explore the tolerance and enrichment and transport characteristics of I.ensata were explored through greenhouse pot experiments,aiming to provide a theoretical basis for garden application and ecological restoration.The main results are as follows:（1）In terms of growth,single and combined stress of zinc and nickel had negative effects on I.ensata.Compared with control group（CK）,The shoot height,root length,leaf width,leaf area and biomass of each treatment decreased under three different treatments,and the higher the stress concentration,the greater the decrease.（2）In terms of physiology and biochemistry,I.ensata had physiological and biochemical responses to single and combined stress of zinc and nickel.In terms of photosynthesis,with the increase of stress concentration,net photosynthetic rate,stomatal conductance and transpiration rate showed a gradual decrease trend,while intercellular carbon dioxide concentration showed a gradual increase trend.Compared with CK,the content of the chlorophyll a decreased under the three treatments,the content of chlorophyll b and carotenoids had the minimum value at the highest concentration,the total chlorophyll content showed a decreasing trend,The single nickel stress showed a decreasing trend first and then increasing,there was no significant change under the combined stress in chlorophyll a/chlorophyll b.In terms of antioxidant system,the superoxide dismutase（SOD）activity had the maximum value at the highest concentration of each treatment.Under single nickel stress and combined stress,the SOD activity had the maximum value at the highest stress concentration,which was4 times and 3.1 times of CK,and single zinc stress had the maximum value at 1000mg·kg^-1.The catalase（CAT）activity had a maximum value at 400mg·kg^-1 under single nickel stress,under combined stress,the result showed an increasing trend first and then decreasing,under single zinc stress,the CAT activity had a minimum value at 2000mg·kg^-1.The glutathione（GSH）content of the three stress treatments showed a gradually increasing trend.under single zinc stress.The oxidized glutathione（GSSG）content had a maximum value at 500mg·kg^-1,and the rest had a maximum value at the highest concentration.The ratio of GSH/GSSG gradually increased under single nickel stress,and reached the maximum at 2000mg·kg^-1 under single zinc stress,and reached the maximum at the highest concentration under combined stress.In terms of osmotic adjustment,with the increase of stress concentration,the soluble protein content showed an increasing trend first and then decreasing under single zinc stress and single nickel stress,while the combined stress showed a gradual increase.Under single nickel stress and combined stress,the soluble sugar content increased first and then decreased,and the maximum value was at 2000mg·kg^-1 under single zinc stress.The proline content of single zinc stress and single nickel stress showed an increasing trend,and combined stress had the maximum value at the highest concentration stress.the content of malondialdehyde（MDA）had the maximum value at the highest concentration under three different stresses.The relative conductivity of single zinc stress and combined stress increased gradually,and the maximum value was at 400mg·kg^-1 under single nickel stress.Through principal component analysis of growth and physiological indexes,it was found that under single zinc stress,I.ensata mainly resisted zinc stress by accumulating proline,controlling stomatal opening and closing,changing photosynthetic rate,regulating growth,producing a large amount of GSH and increasing SOD activity.Under single nickel stress,I.ensata resisted nickel stress mainly by producing GSH,regulating photosynthesis,enhancing peroxidase（POD）activity and regulating growth.Under the combined stres,I.ensata mainly resisted the combined stress by regulating photosynthesis,regulating growth,increasing soluble protein and proline content,increasing POD activity and increasing GSH content.（3）In terms of enrichment and transport,the enrichment content showed that the underground part content>the aboveground part content under single and combined stress of zinc and nickel,and the total enrichment content was positively correlated with the stress concentration.With the increase of stress concentration,the transport factor increased gradually under single zinc stress.Under single nickel stress,the transport factor showed an increasing trend first and then decreasing.Under the combined stress of zinc and nickel,the zinc transport factor gradually increased,but the nickel transport factor gradually decreased.（4）In terms of the subcellular distribution of zinc and nickel,the result showed a same rule under single and combined stress of zinc and nickel.The interception of zinc and nickel was mainly based on the cell wall,but when the stress concentration increased,the cell wall and soluble components played a role in interception.