Arbuscular mycorrhizae improves low temperature stress in maize via alterations in host water status and photosynthesis

The effect of arbuscular mycorrhizal (AM) fungus, Glomus etunicatum, on growth, water status, chlorophyll concentration and photosynthesis in maize (Zea mays L.) plants was investigated in pot culture under low temperature stress. The maize plants were placed in a sand and soil mixture at 25°C for 7 weeks, and then subjected to 5°C, 15°C and 25°C for 1 week. Low temperature stress decreased AM root colonization. AM symbiosis stimulated plant growth and had higher root dry weight at all temperature treatments. Mycorrhizal plants had better water status than corresponding non-mycorrhizal plants, and significant differences were found in water conservation (WC) and water use efficiency (WUE) regardless of temperature treatments. AM colonization increased the concentrations of chlorophyll a, chlorophyll b and chlorophyll a + b. The maximal fluorescence (Fm), maximum quantum efficiency of PSII primary photochemistry (Fv/Fm) and potential photochemical efficiency (Fv/Fo) were higher, but primary fluorescence (Fo) was lower in AM plants compared with non-AM plants. AM inoculation notably increased net photosynthetic rate (Pn) and transpiration rate (E) of maize plants. Mycorrhizal plants had higher stomatal conductance (g_s) than non-mycorrhizal plants with significant difference only at 5°C. Intercellular CO₂ concentration (Ci) was lower in mycorrhizal than that in non-mycorrhizal plants, especially under low temperature stress. The results indicated that AM symbiosis protect maize plants against low temperature stress through improving the water status and photosynthetic capacity.