Peróxido de hidrogênio como mitigador do estresse salino no cultivo irrigado de gravioleira.

Abstract

Soursop cultivation is socioeconomically important for the Brazilian Northeast region due to its economic and social importance in agribusiness. However, in this region, the concentrations of dissolved salts present in the water associated with long periods of drought during several months of the year affect the growth and development of plants, making it necessary to use technologies that mitigate the harmful effects of saline stress on plants. Based on the above, this research evaluated the growth, physiology and mineral composition of the soursop tree cv. Morada Nova due to irrigation with saline water and foliar application of hydrogen peroxide. The experiment was conducted in a greenhouse on a soil classified as a regolith neosol with a sandy loam texture, in the municipality of Campina Grande-PB, during the period from April 2020 to April 2023. The experimental design of randomized blocks was used, in 4 × 4 factorial scheme, with four levels of electrical conductivity of irrigation water - CEa (0.8; 1.6; 2.4 and 3.2 dS m-1) and four concentrations of hydrogen peroxide - H2O2 (0, 10, 20 and 30 µM) with three replicates, totaling 48 experimental plots. At 210 days after transplanting, irrigation with water with electrical conductivity above 0.8 dS m-1 inhibited stomatal conductance, internal CO2 concentration, transpiration, maximum fluorescence, crown height and vigor index vegetative soursop tree cv. Morada Nova and at 370 DAT, stomatal conductance, CO2 assimilation rate, instantaneous carboxylation efficiency, leaf water saturation deficit, chlorophyll a and b biosynthesis and the growth of soursop plants decreased. Foliar application of hydrogen peroxide at concentrations of 12, 18 and 15µM, respectively, attenuated the effects of saline stress on stomatal conductance, CO2 assimilation rate and chlorophyll a synthesis of soursop plants, 780 days after the transplant. The hydrogen peroxide concentration of 30 µM intensified the salt stress on gas exchange, variable fluorescence and electrolyte extravasation in the leaf blade and on the leaf nitrogen, phosphorus and potassium contents of soursop plants cv. Morada Nova, 780 days after transplanting.