Effects Of Ozone Pollution On Membrane Lipid Peroxidation And Antioxidant Function Of Vegetables

The increased concentration of ozone in the near-surface layer has caused great harm to human health,agricultural production,and forest ecology.O₃ pollution can also cause harm to vegetables,reduce vegetable biomass and yield,and cause economic losses.In order to reveal the intrinsic response mechanism of vegetables to O₃ pollution,studies were conducted on the effects of O₃ pollution on the membrane peroxidation and antioxidant properties of vegetables.The research was conducted on Brassica campestris ssp.pekinensis,Brassica campestris,Brassica pekinensis,Lactuca sativa var.longifolia,Ipomoea aquatica,Lactuca sativa var.ramosa,Raphanus sativus var.radculus,Spinacia oleracea,Cucumis sativus and Phaseolus vulgaris.Ten vegetables were used as research objects.Using an open top chamber（OTC）,the experimental subjects were fumigated with four O₃ concentrations:NF（ambient atmospheric O₃ concentration）,NF40(NF+40 nmol·mol^-1),NF80(NF+80 nmol·mol^-1),and NF120(NF+120 nmol·mol^-1).After the start of the fumigation experiment,regularly collect fixed leaf leaves and measure the malondialdehyde（MDA）,reduced ascorbic acid（reduced AsA）,total ascorbic acid（total AsA）,reduced glutathione（GSH）,and total antioxidant capacity（T-AOC）of vegetable leaves.Through statistical analysis of the above physiological and biochemical indicators,the main research results are as follows:1.Response characteristics of MDA content:（1）Compared with the control group,O₃fumigation treatment resulted in an increase in MDA content in the leaves of ten vegetables,and the overall performance showed a positive correlation with the increase in O₃concentration.The MDA content of Ipomoea aquatica leaves fluctuated among the experimental groups along with the experimental process.（2）With the prolongation of fumigation time,the MDA content of Brassica campestris ssp.pekinensis,Brassica campestris,Lactuca sativa var.longifolia,Raphanus sativus var.radculus and Phaseolus vulgaris generally showed a trend of first increasing and then decreasing.Lactuca sativa var.ramose and Spinacia oleracea show a gradual upward trend,while Ipomoea aquatica shows a trend of first decreasing,then increasing,and then decreasing.The trend of changes over time in the experimental groups of Brassica pekinensis and Cucumis sativus is not the same.The MDA content of various vegetables exhibits different changes with the prolongation of fumigation time.（3）The MDA content of nine vegetables except Phaseolus vulgaris was significantly positively correlated with AOT40（P<0.01）.2.Response characteristics of reduced AsA content:（1）Compared with the control group,O₃ fumigation treatment resulted in an increase in the content of reduced AsA in the leaves of ten vegetable species,and generally showed a trend of increasing with the increase in O₃concentration.（2）With the prolongation of fumigation time,the content of reduced AsA in Brassica campestris ssp.pekinensis,Brassica campestris,Brassica pekinensis,Lactuca sativa var.longifolia,Ipomoea aquatica and Cucumis sativus showed a trend of first increasing and then decreasing.The content of reduced AsA in Raphanus sativus var.radculus gradually increased,while the content of reduced AsA in Lactuca sativa var.ramosa,Spinacia oleracea and Phaseolus vulgaris showed fluctuations with time in each experimental group.The reduced AsA content of various vegetables exhibits different changes with the prolongation of fumigation time.（3）There was no significant correlation between the reduced AsA content in the leaves of Ipomoea aquatica and Phaseolus vulgaris and AOT40（P>0.05）,while there was a significant positive correlation between the reduced AsA content and AOT40 in the other eight vegetables（P<0.01）.3.Response characteristics of total AsA content:（1）With the increase of O₃ concentration,the variation trend of total AsA content in leaves of ten kinds of vegetables is different.The total AsA content of Brassica pekinensis,Ipomoea aquatica,Raphanus sativus var.radculus and Cucumis sativus increased compared to the control group.The other six vegetables showed fluctuating characteristics along with the experimental process.（2）With the extension of fumigation time,the total AsA content of Brassica campestris,Lactuca sativa var.longifolia and Ipomoea aquatica showed a trend of first increasing and then decreasing,while Raphanus sativus var.radculus and Spinacia oleracea showed a trend of first decreasing and then increasing.The experimental groups of Brassica campestris ssp.pekinensis,Brassica pekinensis,Lactuca sativa var.ramosa,Cucumis sativus and Phaseolus vulgaris showed different trends over time.The total AsA content of various vegetables showed different changes with the prolongation of fumigation time.（3）There was a significant positive correlation between the total AsA content of Brassica campestris ssp.pekinensis,Brassica campestris,Lactuca sativa var.ramosa,Raphanus sativus var.radculus,Spinacia oleracea,Cucumis sativus and AOT40（P<0.05）,but there was no significant correlation between the total AsA content of Brassica pekinensis,Lactuca sativa var.longifolia,Ipomoea aquatica,Phaseolus vulgaris and AOT40（P>0.05）.4.Response characteristics of GSH content:（1）Compared with the control group,O₃fumigation treatment resulted in an increase in GSH content in all ten vegetables,and generally showed a trend of increasing with the increase in O₃ concentration.However,there were differences in different experimental groups of Brassica campestris,Ipomoea aquatica,Lactuca sativa var.ramosa,Cucumis sativus and Phaseolus vulgaris.（2）With the prolongation of fumigation time,the change trend of GSH content in leaves of ten kinds of vegetables in each experimental group is different,showing an overall upward trend,which is higher in the late stage of fumigation than in the early stage.（3）There was a significant positive correlation between GSH content in leaves of ten vegetable species and AOT40（P<0.01）.5.Response characteristics of T-AOC content:（1）Compared with the control group,O₃fumigation treatment led to an overall increase in T-AOC in vegetables,and generally increased with the increase in O₃ concentration.T-AOC of Lactuca sativa var.longifolia decreased in the experimental group compared to the control group.（2）With the extension of fumigation time,T-AOC in leaves of ten kinds of vegetables showed different changes.On the whole,the T-AOC of Brassica campestris ssp.pekinensis and Brassica pekinensis,showed a trend of first increasing and then decreasing,while that of Raphanus sativus var.radculus gradually increased,while that of Spinacia oleracea first decreased and then increased.The experimental groups of Brassica campestris,Lactuca sativa var.longifolia,Ipomoea aquatica and Lactuca sativa var.ramosa had different trends with time.There was no significant change in T-AOC of Cucumis sativus and Phaseolus vulgaris（3）There was no significant negative correlation between T-AOC content in Lactuca sativa var.longifolia and exposure dose AOT40,and there was no significant positive correlation between T-AOC content in cucumbers（P>0.05）.There was a significant positive correlation between T-AOC content in the other eight vegetables and exposure dose AOT40（P<0.01）.6.Through the analysis of the sensitivity of various physiological indicators of vegetables to O₃,it was found that compared with the control group,O₃ stress reduced the sensitivity of vegetables,and overall,the higher the environmental O₃ concentration,the lower the sensitivity of physiological indicators related to antioxidant activity in vegetables.From the perspective of time course,the sensitivity of ten vegetables to O₃ fluctuated differently with the prolongation of fumigation time.The sensitivity of MDA content to O₃ in ten vegetables gradually decreased overall.The sensitivity of reduced AsA content varies among experimental groups and stages.The sensitivity of total AsA content to O₃ in Brassica campestris ssp.pekinensis,Brassica campestris,Brassica pekinensis,Lactuca sativa var.longifolia,Ipomoea aquatica and Lactuca sativa var.ramosa showed a trend of first increasing and then decreasing,while Raphanus sativus var.radculus,Spinacia oleracea,Cucumis sativus and Phaseolus vulgaris generally showed a trend of first decreasing and then recovering.The sensitivity of GSH content to O₃ in Brassica campestris ssp.pekinensis,Ipomoea aquatica and Raphanus sativus var.radculus showed a trend of first increasing,then decreasing,and then increasing.Brassica campestris,Lactuca sativa var.ramosa and Spinacia oleracea showed a trend of first increasing,then decreasing.Lactuca sativa var.longifolia and Phaseolus vulgaris gradually decreased,while Brassica pekinensis first decreased,and then increasing,with differences among various species.The sensitivity of T-AOC levels to O₃ in Brassica campestris ssp.pekinensis,Brassica campestris,Brassica pekinensis and Ipomoea aquatiac increased first and then decreased,while the sensitivity of Spinacia oleracea to O₃ gradually decreased.Raphanus sativus var.radculus,Cucumis sativus and Phaseolus vulgaris first decreased and then increased.7.Through the correlation analysis of various physiological indicators of vegetables,it was found that there were differences in the correlation between various physiological indicators of ten vegetables.Among them,there was a significant positive correlation between the physiological indicators of Brassica campestris ssp.pekinensis,Brassica campestris,Lactuca sativa var.ramosa and Raphanus sativus var.radculus（P<0.01）,and it significantly increased with the prolongation of fumigation time.8.Through redundancy analysis of vegetable varieties,physiological indicators,and concentration time,it was found that O₃ concentration and time treatment were positively correlated with physiological indicators,and there was a positive correlation between various physiological indicators.The results of principal component analysis showed that the correlation between reduced AsA,total AsA,and T-AOC was high,while the correlation between MDA and GSH was high.The physiological responses of different vegetable varieties to O₃ stress were different.9.The results of principal component analysis showed that T-AOC level was the most important antioxidant physiological index of vegetables under O₃ stress,followed by GSH content.The order of tolerance to O₃ stress in ten vegetables is:Spinacia oleracea>Phaseolus vulgaris>Cucumis sativus>Brassica campestris>Brassica campestris ssp.pekinensis>Raphanus sativus var.radculus>Brassica pekinensis>Lactuca sativa var.ramosa>Lactuca sativa var.longifolia>Ipomoea aquaticaIn summary,there are differences in the response characteristics of physiological indicators related to membrane lipid peroxidation and antioxidant function of ten vegetables to O₃ stress at different concentrations and fumigation times.Overall,under O₃ stress,the content of MDA in vegetable leaves increased,and the degree of membrane lipid peroxidation increased.Vegetables increased their antioxidant capacity by increasing the content of AsA and GSH,and their total antioxidant capacity increased.With the prolongation of fumigation time,the sensitivity of various antioxidant physiological indicators of vegetables to O₃ stress decreased,indicating that vegetables have developed a certain degree of adaptation to O₃ stress.