Caracterização biométrica e bioquímica de cultivares de soja submetidas ao déficit hídrico severo

Abstract

Water deficit (DH), considered one of the main limiting factors in agriculture, affects the growth, development, and biochemical responses of numerous crops. Plants respond to it in a complex way, involving a range of factors related to genetic, morphological, physiological and biochemical characteristics. In this sense, this work aimed to determine, through a biometric and biochemical characterization, the degree of tolerance to water deficit of four commercial high-yield soybean cultivars. The experiment was carried out in a greenhouse, under a completely randomized 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 biometric variables evaluated were: absolute growth rate (TCA), relative growth rate (TCR), specific leaf area (AFE), leaf area ratio (RAF), leaf mass ratio (RMF), stem mass ratio (RMC), root mass ratio (RMR), root/shoot ratio (R/PA); and the biochemical variables were: soluble carbohydrates, soluble N-amino, soluble proteins, proline, and the activities of the enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (GPOD). The isolated factor DH reduced about 23.73% of the absolute growth rate, 18.15% of the relative growth rate, 14.79% of the R/PA ratio, compared to the control treatment. For biochemical analysis, water stress increased about 24.51% proline, 46.74% soluble N-amino, 19.4% soluble carbohydrates, 12.98% soluble proteins, 9.76% APX enzyme activity and 40.97% of the GPOD enzyme, in relation to the control treatment. The cultivars Monsoy 8644 and Extrema IPRO showed the best results for the biometric variables, showing better plant development. Exposure to water deficit caused the cultivars to increase the amount of organic solutes, especially the cultivar Extrema IPRO. It can be concluded that the water deficit is unfavorable for the growth rate and mass ratios in soybean plants, regardless of the cultivar. The cultivars Extrema IPRO and TMG 2383 showed superior root elongation and the highest activities of the antioxidant system, indicating greater tolerance to DH in relation to the other cultivars, and may be indicated for cultivation in the Northeast region.