Effects of Arbuscular Mycorrhizal Fungi on Photosynthetic Characteristics in Leaves of Flue-cured Tobacco

The effects of AM fungi on agronomic attribute, dry matter accumulation, gas exchange parameters, chlorophyll, chlorophyll fluorescence parameters of flue-cured tobacco were studied by pot experiments in order to investigate the tobacco growth effect of the AM fungi inoculation. The results showed that AM fungi inoculation increased significantly tobacco biomass. The agronomic attributes in various growth stages and root cap ratio effects varied with types of AM fungi. Inoculation of AM fungi resulted in increase of net photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll a/b value, the maximum quantum yield of PSII, relative maximal electron transport rate and onset of light saturation in leaves, but the intercellular CO₂ concentration and stomatal limitation value did not change significantly. There were differences between different AM Fungi on the total chlorophyll content, carotenoid content, chlorophyll a content, chlorophyll b content and the PS II potential activity in tobacco leaves, but the initial slope was lower than in non-AM plants. The results demonstrated that inoculation of AM fungi might enhance the PSII reaction centers in leaves, which caused photosynthetic organization in leaves were more tolerant to strong light and more conducive to photosynthesis, but the effects of AM fungi promoted the growth of flue-cured tobacco varied.