Beneficial roles of arbuscular mycorrhizas in citrus seedlings at temperature stress

Citrus, a cold-sensitive plant, often suffers from low temperature, which seriously affects citrus productivity. The objective of the study was to elevate the roles of an arbuscular mycorrhizal fungus, Glomus mosseae, in growth, photosynthesis, root morphology and nutrient uptake of citrus (Citrus tangerine) seedlings under temperature stress conditions. Three-month-old seedlings with or without G. mosseae were grown for 55 days at moderate temperature (25 °C) and low temperature (15 °C). Low temperature severely restrained symbiotic development including mycorrhizal colonization, entry point, vesicle and arbuscule relative to moderate temperature. Mycorrhizal seedlings grown at 25 °C maintained better stem diameter, plant height, leaf area, root and total dry weights, higher photosynthetic rate, transpiration rate and stomatal conductance, higher root volume, and more uptake of P, Ca and Mg relative to corresponding non-mycorrhizal control. However, mycorrhizal inoculation significantly increased only the root length and the Ca content of the seedlings grown at 15 °C. The results indicated that mycorrhizal formation had the beneficial effects on growth, photosynthesis, root morphology and part nutrient uptake of citrus seedlings grown at moderate temperature, but the beneficial roles of arbuscular mycorrhizas were almost lost at low temperature.