Hydrogen peroxide on acclimation of soursop seedlings under irrigation water salinity

The Brazilian Northeast region provides favorable conditions for the exploitation of several crops, but the high salt concentration in irrigation water constitutes a limiting factor for production in most cases. In this context, this study aimed to evaluate the emergence, growth and partition of photoassimilates in soursop seedlings, cv. ‘Morada Nova’, subjected to irrigation with water of increasing salinity levels and to exogenous application of hydrogen peroxide. The study was carried out in plastic bags under greenhouse conditions, using a sandy loam Regolithic Neosol, in the municipality of Campina Grande, PB, Brazil. Treatments were distributed in randomized blocks, in a 5 x 5 factorial arrangement, relative to five levels of irrigation water electrical conductivity - ECw (0.7, 1.4, 2.1, 2.8 and 3.5 dS m-1) and five concentrations of hydrogen peroxide - H2O2 (0, 25, 50, 75 and 100 µM), with four replicates and three plants per plot. Increasing salt concentration compromised all variables analyzed and leaf area was most sensitive. As irrigation water electrical conductivity increased, the deleterious effects of water salinity on the emergence percentage, emergence speed index, stem diameter and leaf area were attenuated by the exogenous application of hydrogen peroxide, with highest efficiency at the concentration of 50 µM. Hydrogen peroxide concentrations above 38 µM inhibited the specific leaf area of soursop, cv. ‘Morada Nova’.