低温胁迫下亚精胺对菜豆幼苗PSⅡ功能及叶绿素代谢关键基因表达的影响OA

In this study,the effects of 1.0 mmol·L-1 exogenous spermidine(Spd)and methylglyoxal diamidine hydrazone(MGBG)on the growth,chlorophyll content,photosystemⅡ(PSⅡ)function,chlorophyll degradation and synthase activity and related gene expression of common bean seedlings under low temperature stress were investigated at 12℃/8℃.The results indicated that compared with the control,low-temperature stress inhibited the growth of seedlings;chlorophyll content maximum photochemical efficiency of PSⅡ(Fv/Fm),photochemical quenching coefficient(qP),electron transport rate(ETR)and actual photochemical efficiency(ΦPSII)were all significantly reduced(P<0.05);while non-photochemical quenching coefficient(qN)significantly increased(P<0.05).Under low-temperature stress,the chlorophyll fluorescence induction(OJIP)curve showed significant alterations:the fluorescence intensities at the J-and P-steps were reduced,while the heat dissipation per unit cross-section(DIo/CSm)and energy dissipation per reaction center(DIo/RC)were markedly elevated.Under low temperatures(T2),the application of Spd reversed the aforementioned trends,with significant increases in light energy absorption(ABS/CSm),conversion(TRo/CSm),and electron transport(ETo/CSm).Spd-induced downregulation of key chlorophyll degradation genes PvCLH1(chlorophyllase 1)/PvCLH2(chlorophyllase 2)and PvRCCR1(red chlorophyll metabolite reductase 1)resulted in decreased chlorophyllase(CLH)activity;Key chlorophyll synthesis genes PvPOR1(proto-deplastidic chlorophyll reductase 1)/PvPOR2(proto-deplastidic chlorophyll reductase 2)showed significantly increased relative expression(P<0.05),with elevated chlorophyll acidase activity.The results indicate that exogenous Spd alleviates the suppression of photosynthesis in common bean seedlings under low-temperature stress by upregulating the expression of chlorophyll synthesis-related genes,increasing chlorophyll content,and enhancing the absorption and utilization of light energy by PSⅡ.