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Low-temperature and weak-light conditions have major effects on the growth and flower quality of horticultural plants. A greenhouse pot experiment was performed to investigate the effects of arbuscular mycorrhizal fungi (AMF) (Funneliformis mosseae and Glomus versiforme) on the growth, photosynthesis, and chlorophyll fluorescence parameters of snapdragon (Antirrhinum majus L.) under low-temperature and weak-light stress. The growth and biomass of snapdragon were higher following inoculation with F. mosseae and G. versiforme compared with control plants. The percentage of mycorrhizal colonization and root activity were high in A. majus plants with AMF. AMF inoculation enhanced the net photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency of plants under low-temperature and weak-light conditions. Furthermore, the chlorophyll content, potential activity of photosystem II (PSII), effective photochemistry quantum efficiency of PSII, actual photochemical quantum efficiency of PSII, and photochemical quenching coefficient were higher in AMF-inoculated plants than in uninoculated plants. The application of AMF reduced the intercellular CO2 concentration and non-photochemical quenching coefficient. Thus, snapdragon plants treated with F. mosseae and G. versiforme are more resistant to low-temperature and weak-light stress than untreated plants.

It is well documented that arbuscular mycorrhizal fungi (AMF) affect growth and nutrient absorption in host plants under pot conditions. However, their effects on reproductive growth in ornamental plants under field conditions are unknown. Our study evaluated the effects of AMF on flowering and physiological traits in snapdragon (Antirrhinum majus) under greenhouse field conditions. Seedlings were inoculated with Funneliformis mosseae (Nicolson & Gerd.) and without as controls. Results showed that AMF inoculation significantly increased plant height, stem diameter, phosphorus, and soluble protein; decreased soluble sugar; and had no effect on total nitrogen, carbon, and potassium. AMF colonization increased concentrations of abscisic acid (ABA), indol-3-acetic acid (IAA), gibberellin (GA3), and zeatin riboside (ZR); increased the ZR/IAA ratio; and reduced ABA/GA3 and ABA/IAA+GA3+ZR ratios. AMF advanced flowering by five days and prolonged flowering by 13 days. Our study showed that AMF can promote flowering and prolong flowering in snapdragon, which may be due to the improvement of endogenous hormone equilibrium.