模拟道路交通NO2对观赏植物三角梅形态、生理和代谢组学的影响OA

[Objective]Under laboratory conditions simulating roadside NO2 exposure,this study investigated the leaf morphological,physiological,biochemical,and metabolomic responses of the urban roadside greening plant Bougainvillea×buttiana'Miss Manila'to long-term NO2 exposure,aiming to clarify the mechanisms underlying plant responses to NO2 and to provide a theoretical basis for the precise selection and management of urban greening plants.[Method]The common ornamental cultivar B.×buttiana'Miss Manila'was used as the experimental material.In a fully automated closed fumigation system,plants were exposed to three treatments:clean air as the control(CK),class I NO2 concentration(T1,0.02 μL·L-1),and class II NO2 concentration(T2,0.04 μL·L-1).During the treatment period,plant phenotype,photosynthetic parameters,and metabolic regulation related indicators were dynamically monitored.After exposure,leaf nitrogen metabolism,microstructure,and metabolomic profiles were comparatively analyzed.[Result]1)With prolongation of fumigation time,NO2 significantly inhibited the growth and photosynthetic rate of B.×buttiana'Miss Manila'and altered the contents of physiological regulatory substances.Under the class II concentration,the leaf integrity index and the activities of superoxide dismutase and catalase decreased by 50.14%,31.58%,and 46.81%,respectively,whereas the contents of malondialdehyde,proline,and soluble protein increased by 43.50%,149.02%,and 22.72%,respectively.2)Compared with the control,T2 treatment significantly reduced leaf chlorophyll content,net photosynthetic rate,and photochemical efficiency,damaged the leaf cuticular structure,disrupted epidermal cells and chloroplast structure,significantly enhanced the activities of nitrogen metabolism-related enzymes,and increased oxidized nitrogen content by 158.43%.3)After conducting correlation analysis and cluster analysis on the 22 selected indicators,two major groups were divided on their basic response patterns:the first group comprised chlorophyll fluorescence parameters and antioxidant enzyme indicators,and the second group comprised nitrogen forms and nitrogen metabolism-related enzyme indicators.Compared with the control,the overall response trend of B.×buttiana'Miss Manila'under T1 and T2 treatments was similar,but their temporal trajectories were non-linear.4)NO2 stress induced systemic metabolic responses,with significant changes in the contents of multiple metabolites,including L-leucine and α-linolenic acid.These changes mainly involved metabolic pathways of amino acids,α-linolenic acid,and betalain.KEGG enrichment analysis showed that metabolic pathways such as betalain biosynthesis and glutathione metabolism had relatively high enrichment factors,and the substrate content in the corresponding pathways significantly decreased,showing dose-dependent responses.[Conclusion]Inhibition of key metabolite synthesis and disruption of cellular structure may be important causes of the reduced resistance in B.×buttiana'Miss Manila'under NO2 stress,and NO2 exposure markedly alters its metabolic profile.Overall,high-concentration and long-term NO2 exposure have stronger negative effects,whereas short-term exposure to low-concentration NO2 shows a certain low-dose stimulatory effect.Therefore,in roadside environments with long-term high NO2 concentrations,B.×buttiana'Miss Manila'should be planted in combination with other plant species rather than as a single dominant species.