Papel de compostos orgânicos e inorgânicos na tolerância à seca em plantas de soja

Abstract

Soybean is the crop with the highest economic value, with Brazil being the world's largest producer and exporter of this legume. Water deficit is the stress that most compromises the physiological processes of plants, decreasing plant growth and productivity. Substances such as proline, glycine-betaine, nitric oxide and potassium phosphite can help protect plants against abiotic stresses such as water restriction. Thus, the objective of this study was to determine the effects of water deficit on water relations, gas exchange and biometric parameters of soybean, in view of the application of stress-mitigating compounds, as well as to establish a better formulation. The experiment was carried out in a greenhouse in a controlled environment, with a randomized block design with 5 replications and AxB 2x4 factorial arrangement, with factor A being the field capacities (FC) of the soil of 90% (control) and 50% (water deficit), and factor B, applications of 0 (water), formulation 1 (30 mM proline, 15 mM glycine-betaine, 300 µM sodium nitroprusside (SNP) and 1 L Ha-1 phosphite of potassium), formulation 2 (45 mM proline, 22.5 mM glycine-betaine, 450 µM SNP and 1.5 L Ha-1 potassium phosphite), and formulation 3 (60 mM proline, 30 mM of glycine-betaine, 600 µM of SNP and 2 L Ha-1 of potassium phosphite), totaling 40 experimental units. The treatments were imposed at the beginning of the flowering of the soybean plants, by means of spraying and beginning of water restriction in the soil. The plants were under water deficit for 11 days, and then analyzes of pigments, water relations, gas exchange, chlorophyll a fluorescence and biometric parameters were performed. Even with the application of stress-relieving substances, WD had a negative impact on photosynthetic, fluorescence, gas exchange and biometric parameters. The substances applied did not increase the tolerance of soybean plants in this study. For a better elucidation of the effects of the use of stress-relieving substances in a combined way in plants under water stress, it is also necessary to carry out production, biochemical and reproductive analyses.