Influência da densidade de esporos de fungos micorrízicos arbusculares nativos da savana no desenvolvimento do milho (Zea Mays)

Abstract

In the symbiotic relationship between arbuscular mycorrhizal fungi (AMF) and plants, AMF assists in the absorption of water and mineral nutrients by plants, in contrast, plants supply carbohydrate to AMF, however, the uncontrolled proliferation of AMF can be harmful to plants. We evaluated the effect of arbuscular mycorrhizal fungi originated from the soil of a savanna area in Alter do Chão, in the eastern Brazilian Amazon, on the initial growth and carbohydrate metabolism of corn seedlings. Corn plants were inoculated with different densities of AMF spores using three treatments (T1=3.8; T2= 7.6 and T3=30 spores g-1 of soil) and AMF-free soil as control in a greenhouse experiment. The corn shoots were evaluated 18 days after emergence for growth parameters and quantification of carbohydrate content in the roots and aerial parts. Shoots treated with T3 had significantly smaller aerial parts, height, stem diameter, lower leaf and total mass than the control. The root/aerial parts ratio was significantly higher in the T3 and T1 treatments relative to the control. Total soluble sugar, non-reducing sugar and starch contents did not vary significantly in the root and aerial parts, except for significantly lower starch contents in the T3 and T1 treatments than in the control. Reducing sugar content was significantly higher in the aerial parts of the T2 and T1 treatments. We conclude that the spore density of T3 has negative effects on corn growth, but that the densities of the T1 e T2 have a positive effect on the reducing-sugar balance, which may confer a greater tolerance to the water déficit