Leaf photosynthesis and yield components of mung bean under fully open-air elevatedCO2

摘要

cqvip:Mung bean(Vigna radiata L.) has the potential to establish symbiosis with rhizobia,and symbiotic association of soil micro flora may facilitate the photosynthesis and plant growth response to elevated[CO_2].Mung bean was grown at either ambient CO_2 400 μmol mol^(-1) or[CO_2]((550+17) μmol mol^(-1)) under free air carbon dioxide enrichment(FACE) experimental facility in North China.Elevated[CO_2]increased net photosynthetic rate(P_n),water use efficiency(WUE) and the non-photochemical quenching(NPQ) of upper most fully-expanded leaves,but decreased stomatal conductance(G_s),intrinsic efficiency of PSII(F_v '/F_m'),quantum yield of PSII(φ_(PSll)) and proportion of open PSII reaction centers(q_p).At elevated[CO_2],the decrease of F_v'/F_m',φ_(PSII),q_p at the bloom stage were smaller than that at the pod stage.On the other hand,P_n was increased at elevated[CO_2]by 18.7 and 7.4%at full bloom(R2) and pod maturity stages(R4),respectively.From these findings,we concluded that as a legume despite greater nutrient supply to the carbon assimilation at elevated[CO_2],photosynthetic capacity of mung bean was still suppressed under elevated[CO_2]particularly at pod maturity stage but plant biomass and yield was increased by 11.6 and 14.2%,respectively.Further,these findings suggest that even under higher nutrient acquisition systems such as legumes,nutrient assimilation does not match carbon assimilation under elevated[CO_2]and leads photosynthesis down-regulation to elevated[CO_2].