Crescimento e desempenho fisiológico de cultivares de soja submetidas ao déficit hídrico severo

Abstract

The drought stress (DH), caused by prolonged periods of dry, represents a problem for the development and productivity of agricultural crops, such as soybeans, requiring the use of cultivars with a higher degree of tolerance to this condition for agricultural success. In this sense, this study aimed to determine, through a physiological and growth characterization, the degree of tolerance to water deficit in four commercial soybean cultivars for high yield. The experiment was carried out in a greenhouse, using a completely randomized experimental design, in a 2 x 4 factorial scheme, referring to two water conditions (irrigated and water deficit) and four commercial soybean cultivars indicated for the Northeast (Brasmax Extrema IPRO, Monsoy 8644, Monsoy 8349 and TMG 2383) with five replications, totaling 40 experimental units. The variables evaluated were: biometric variables (plant height, stem diameter, total leaf area, dry mass of the aerial part, dry mass of the root, root volume and root length); gas exchange variables and chlorophyll a fluorescence (liquid photosynthesis, stomatal conductance, transpiration, instant carboxylation efficiency, water use efficiency, PSII potential photochemical efficiency, FSII effective quantum yield, electron transport rate, photochemical quenching, non-photochemical quenching and non-photochemical extinction coefficient); photosynthetic pigments (relative index of chlorophyll, chlorophyll a, b, total and carotenoids); relative water content and electrolyte leakage. The isolated factor DH reduced about 11.47% of the height, 24.87% of the leaf area, 22.15% of the dry mass of the aerial part, 33.89% of the dry mass of the root, 47.22% of the root volume , 9.47% of the root length, 38.89% of photosynthesis, 9.33% of the Fv / Fm ratio, 44.47% of chlorophyll b, 9.77% of the relative chlorophyll index, 13.05% and 9 , 37% of the relative water content, compared to the control treatment. The cultivars Monsoy 8349 and Extrema IPRO showed good physiological results, which reflected in a better development of the plants. The cultivars Monsoy 8644 and TMG 2383, in spite of the good results, did not show good growth (biometric parameters), indicating a certain sensitivity to HD. It can be concluded that the water deficit was unfavorable for growth and physiological performance in high yield soybean cultivars. The cultivars Monsoy 8349 and Extrema IPRO showed a higher degree of tolerance to water deficit, which can be indicated for cultivation in the Northeast region.