UV-B辐射对马蓝幼苗抗氧化和光合能力的影响OA

To investigate the effects of UV-B radiation on the growth and photosynthetic performance of Baphicacanthus cusia seedlings,seedlings were exposed to simulated high-intensity UV-B radiation(1 000 μW·cm-2)for 0,1,3 and 5 h,and multiple physiological parameters including growth traits,antioxidant enzyme activity,and photosynthetic performance were systematically evaluated.The results showed that UV-B radiation significantly inhibited seedling growth,particularly after 5 h of exposure.Relative to the control group(0-hour exposure),the UV-B-treated leaves exhibited significant reductions in total chlorophyll content,maximum quantum yield of PS Ⅱ(Fv/Fm),photo-oxidizable PS Ⅰ(Pm),net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),intercellular CO2 concentration(Ci),and the abundance of key thylakoid membrane proteins(D1,D2,Lhca1).Concomitant genomic DNA damage was also detected.UV-B radiation triggered substantial accumulation of superoxide radical(O2-·)and hydrogen peroxide(H2O2),accompanied by elevated malondialdehyde(MDA)levels and increased relative electrical conductivity.The antioxidant system exhibited a differential response to UV-B radiation.The activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)increased under short-term UV-B radiation but declined under long-term UV-B radiation,whereas the activity of ascorbate peroxidase(APX)was consistently inhibited across all UV-B treatment groups.Similarly,the content of carotenoid and anthocyanin showed an initial increase under short-term UV-B radiation but decreased after prolonged exposure.Collectively,these results indicate that short-term UV-B exposure(1 and 3 h)activates the protective antioxidant and photoprotective mechanisms in B.cusia seedlings.In contrast,long-term UV-B exposure to(5 h)overwhelms these defensive systems,leading to oxidative damage,irreversible impairment of the photosynthetic apparatus,and eventual plant death.This study elucidates the acute damage symptoms,physiological response mechanisms,and UV-B tolerance thresholds of B.cusia seedlings under high-intensity UV-B radiation,providing a theoretical basis and practical guidance for stress resistance evaluation and optimized cultivation of B.cusia in high-altitude regions.