ALTERAÇÕES FISIOLÓGICAS EM PLANTAS DE SOJA SUBMETIDAS A NÍVEIS DE DÉFICIT HÍDRICO E INOCULAÇÃO COM FUNGOS MICORRÍZICOS ARBUSCULARES

Abstract

Soybean is the most produced and consumed oilseed in the world, and Brazil occupies the first place in the world production of this grain. Agriculture is highly dependent on climatic factors, the summer constants, common in the mid-west, restrain the maximum potential productivity of crops. Water is one of the main resources for crop growth and represents about 90% of soybean plant biomass. Arbuscular mycorrhizal fungi (AMF) play a vital role in nature, which act as an extension of plant roots and maximize nutrient and water absorption effectively. These fungi colonize plants to bring them several advantages, mainly in terms of nutrient accumulation, greater plant growth and productivity enhancement. Moreover, plants that live with these fungi maintain greater stomatic conductance during periods of water scarcity. This study aimed to analyze the physiological performance of soybean plants associated with AMF, under three levels of water deficit. The plants that were inoculated received 31g of the inoculum G. margarita (3.3 g-1 spores) and 46 g of FMA G. gigantea (2.2 g-1 spores) in the sowing groove, separately and grew in a greenhouse under natural conditions of light with RH and average temperature of 28 °C. The control of the water content was performed through irrigation sensors, model 10 HS (METER Group, Inc. USA), after measuring the field capacity using gravimetric method. Water deficit was imposed when the plants reached stage V3, being divided into three groups: 80% of WC, 60% of WC and 40% of WC. Biometric and physiological parameters of the plants were evaluated. After the first analyses, the plants were reirrigated up to 80% of WC for two days and the analyses were performed again. Soybean plants inoculated with AMF G. margarita and G. gigantea showed higher rates of stomatic conductance, transpiration and maximum fluorescence than plants without inoculation. These results demonstrate that plants inoculated with AMF have higher tolerance to water deficit due to the contribution of fungi. The data obtained show that the greater the deficit, the greater the response to AMF inoculation. Therefore, inoculation with AMF G. margarita and G. gigantea maximizes soybean development under water deficit conditions.