Ácido salicílico na indução à tolerância da gravioleira ao estresse salino.

Abstract

The use of saline water in soursop cultivation in the semi-arid region of Northeast Brazil can be made possible through the use of substances that can attenuate the deleterious effects of saline stress, such as salicylic acid. In this context, the objective of the present study was to evaluate the effect of foliar application of salicylic acid concentrations on the growth and physiology of soursop irrigated with saline water. The study was carried out in a greenhouse using drainage lysimeters; a randomized block design and a 5 × 4 factorial arrangement were used, with five levels of electrical conductivity of the irrigation water - ECw (0.8-control; 1.6; 2.4; 3.2 and 4.0 dS m-1) and four concentrations of salicylic acid - AS (0 -control; 1.2; 2.4 and 3.6 mM), with three replications and one plant per plot. The growth variables and photosynthetic pigments were positively influenced by the interaction of the electrical conductivity of irrigation water and salicylic acid concentrations between 1.0 and 2.0 mM. The foliar application of salicylic acid between concentrations of 1.4 and 1.6 mM attenuated the effects of saline stress on the gas exchange of soursop. Foliar application of salicylic acid at a concentration of 1.4 mM increased the levels of photosynthetic pigments in soursop when irrigated with electrical conductivities of up to 1.5 dS m-1. There was no significant interaction of the factors under study on the fluorescence of chlorophyll a in soursop, however, irrigation with water of electrical conductivity up to 1.8 dS m-1 did not compromise the quantum efficiency of photosystem II. The percentage of electrolyte leakage was reduced with foliar application of salicylic acid to a concentration of 1.3 mM. Foliar application of salicylic acid in concentrations greater than 2.0 mM is not recommended, as it intensifies the deleterious effects of irrigation water salinity on growth, gas exchange, photosynthetic pigments and the percentage of water extravasation. electrolytes.