Physiological changes and growth of soursop plants tinder irrigation with saline water and H2O2 in post-grafting phase

The low availability of water associated with high salt concentrations in irrigation water has become one of the leading challenges for agricultural production in the semiarid region of Northeastern Brazil. Thus, the study of strategies to enable the use of saline water in agriculture is essential. From this perspective, this study aimed to evaluate alterations in gas exchange, chloroplast pigments, and cell damage in soursop (Anonna muricata L.) irrigated with saline water and under exogenous application of hydrogen peroxide (Hp) in the post-grafting phase. A study was conducted in Campina Grande. PB, under greenhouse conditions. The treatments were distributed in a randomized block design, in a 4 x 2 factorial arrangement, consisting of four levels of electrical conductivity of water (ECvv, 1.6; 2.4; 3.2 and 4.0 dS m(-1)) and two concentrations of H2O2 (0 and 20 mu M) with four replications. Irrigation water salinity from 1.6 dS m(-1) caused changes in the stomatal conductance, respiration, and internal CO2 concentration of soursop plants. A 20 mu M concentration of H2O2 reduced the effects of salinity on transpiration and CO2 assimilation values, in addition to promoting the biosynthesis of photosynthetic pigments and reducing cell damage in soursop plants, at 150 days after transplantation. The exogenous application of 20 AM H2O2 reduced the deleterious effects of salinity on the stem diameter of both rootstock and scion in soursop plants irrigated with ECw of 1.6 dS m(-1). The exogenous application of 20 mu M H2O2 was not efficient in mitigating the damage caused by salinity on the stem diameter of the soursop at grafting point.