| With the rapid development of human activities and industrialization,a large number of chlorofluorocarbons are released into the air,resulting in the thinning of the atmospheric ozone layer,which significantly increases the level of UV-B radiation reaching the earth's surface.UV-B can damage antioxidant system,protein and cell membrane,reduce photosynthetic activity and hinder plant growth.Wetland biology is an important part of natural ecosystem,which provides important ecological services for human survival and development.Iris wilsonii is one of the most important wetland organisms,which has the functions of water purification and ornamental.In order to further understand the response of antioxidant system and UV absorbing substances of Iris wilsonii leaves to enhanced UV-B radiation,the changes of active oxygen,antioxidant system,isoflavone metabolism and UV absorbing substance content of iris flaviflora leaves under three UV-B levels were studied in constructed wetland,and the adaptability and mechanism of iris flaviflora leaves to enhanced UV-B radiation were analyzed.The main achievements are as follows:1.Under enhanced UV-B radiation,the active oxygen content of the leaves of Iris wilsonii.Under the treatments of 210?w·cm-2and 252?w·cm-2,the average content of O2-and H2O2increased by 16.64%,58.08%and 20.12%,61.82%,respectively.The MDA content increased significantly,and the cell plasma membrane permeability increased significantly.Compared with the control group,the average MDA content and relative conductivity of the low-irradiation group increased by 9.5%and 18.89%,and the average MDA content and relative conductivity of the high-irradiation group increased by 20.25%and 25.35%.Moreover,the damage effect was enhanced with the increase of UV-B radiation intensity and exposure time.2.Under enhanced UV-B radiation,at the fifth day,the As A,DHA,and GSH contents in the leaves of Iris wilsonii reached the highest content,and then it began to decrease.Under the treatment of 210?w·cm-2,the contents of As A,DHA,GSH,and GSSG increased by 218.6%,37.08%,30.07%,and 31.91%,respectively,compared with the control group.Under the treatment of 252?w·cm-2,As A The content of DHA,GSH and GSSG increased by 277.3%,71.57%,97.97%,82.81%respectively compared with the control group.The activities of POD,APX,GR,and CAT in Iris leaves showed an increasing trend with the prolonging of radiation treatment time.The activities of SOD and MDHAR continued to decrease,and the activities of DHAR increased first and then decreased.Under low-dose(210?w·cm-2)UV-B radiation treatment,the activities of SOD,POD,APX,GR,CAT,DHAR and MDHAR in iris leaves increased by 6.31%,7.23%,194.84%,20.65%,56.38%on average compared with the control group,12.83%and 23.07%;under high-dose(252?w·cm-2)UV-B treatment,the average increase in leaf SOD,POD,APX,GR,CAT and DHAR activities were 10.79%,18.59%,331.79%,68.55,respectively%,43.05%and 28.11%,but the MDHAR activity is lower than the control(-1.06%).It shows that under enhanced UV-B radiation,the leaves of Iris odorifera mainly rely on increasing the activities of As A,DHA,GSH,GSSG and APX,CAT,GR and DHAR to resist the stress of reactive oxygen species.The As A-GSH circulatory system plays an important role in the removal of reactive oxygen species.3.The content of 12 kinds of phenolic acids and isoflavones in the leaves of Iris wilsonii was the most abundant(all above 20mg/kg,the control average is98.53mg/kg,under low radiation it is 153.37mg/kg,under high radiation It was122.15mg/kg),vanillic acid followed(all above 7mg/kg,control average 17.86mg/kg,low radiation 24.80mg/kg,high radiation 12.38mg/kg),syringic acid was the lowest(both at 2mg/kg).Under the control group averaged 1.35mg/kg,low radiation group1.02mg,high radiation group 0.35mg/kg).Under low-dose and high-dose enhanced UV-B treatments,the total flavonoid content of Iris iris leaves increased by 9.45%and6.67%,and the total anthocyanin content increased by 5.94%and 18.72%on average.The total phenol content was higher than that under low dose UV-B radiation The control increased by 14.12%and decreased by 6.87%compared with the control under high-dose treatment.Among them,the content of rutin,irisin and irisin increased with the increase of radiation intensity,and ferulic acid,vanillic acid and irisin in low-dose UV The content of-B is higher under enhanced treatment,the content of oridoside,genistein and iris is almost unchanged under the three UV-B radiation treatments,and the content of syringic acid is slightly reduced under the enhanced UV-B treatment.4.Under the conditions of enhanced UV-B radiation,the activity of key enzymes in the metabolic pathway of isoflavones and anthocyanins in the leaves of Iris wilsonii was inconsistent.Under low-dose and high-dose UV-B treatment,respectively,the activities of PAL,CHS,IFS,ANS,LAR,UFGT and DFR in Iris leaves increased with the increase of UV-B radiation dose,and increased by 28.60%and 56.76%,130.66%and 160.70%6.66%and 11.76%,45.86%and 74.49%,15.55%and 31.86%,5.51%and 12.41%,4.74%and 10.63%;the activity of C4H and FLS in the leaves increased at a higher dose than at a high dose,and increased by 26.83%and 16.57respectively compared with the control%,38.00%and 0.91%;CHI and 4CL and activities increased by 17.32%and 3.34%under low-dose UV-B treatment,but decreased by 9.19%and 4.32%under high-dose UV-B treatment;F3H activity decreased by 1.40%under low-dose UV-B treatment,and increased by 7.40%under high-dose UV-B treatment.In the control group and the high UV-B radiation group,the content of syringic acid was extremely negatively correlated with the activity of LAR,and the content of ferulic acid was extremely negatively correlated with the activity of CHI;the content of resveratrol in the control group and the low UV-B radiation group was correlated with The activity of C4H and DFR and the content of iris aglycone were significantly positively correlated with the activities of C4H,DFR and UFGT;in the low UV-B radiation group and the high UV-B radiation group,the rutin content was extremely significantly positively correlated with the F3H activity.The content of phenolic acid compounds and the correlation between total flavonoids and anthocyanidins under the treatment of three intensities of UV-B radiation showed certain differences.The similarities and differences of the compound content in the leaves of iris is mainly because the plant mobilizes the substance content in the body to resist stress damage.5.UV-B radiation can increase the content of ultraviolet absorbing substances in plants.The total anthocyanin content in the leaves of Iris wilsonii was increased,and the average increase was 5.94%and 18.72%under the treatments of 210?w·cm-2and252?w·cm-2.In the low-irradiation group,the content of total phenols and total flavonoids both increased;but in the high-irradiation group,the total flavonoids content changed in a wave shape,that is,first increased,then decreased,and then slightly increased;while the total phenol content decreased slowly afterwards raise again.Under 210?w·cm-2and 252?w·cm-2treatments,the average increase in total phenol content was 14.12%and the decrease was 6.87%,respectively;the average increase in total flavonoid content was 9.45%and 6.67%.In summary,this study analyzed the water and mechanical properties of the soil in the test area,and discussed the conditions of enhanced UV-B radiation in terms of active oxygen production,antioxidant systems,isoflavones and anthocyanidin metabolism,and UV-absorbing substances.The effects and mechanisms of leaf damage,adaptation,and resistance to oxidative stress provide an important empirical basis and mechanism explanation for understanding the adaptation of Iris to enhanced UV-B radiation stress. |
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