Hydrogen peroxide in the induction of tolerance of guava seedlings to salt stress

Guava cultivation plays a significant role in the socioeconomic development of the Brazilian semi-arid region, contributing to employment opportunities and income generation. However, this region often faces the challenge of high levels of dissolved salts in water sources, necessitating strategies to mitigate the adverse effects of salt stress on plants. This study aimed to assess the impact of foliar application of hydrogen peroxide on gas exchange, photochemical efficiency, growth, and quality of guava seedlings subjected to salt stress. The experiment was conducted under greenhouse conditions in Pombal - PB, Brazil, following a randomized block design. The treatments comprised a 5 x 4 factorial arrangement, representing five levels of electrical conductivity in the irrigation water (ECw: 0.3, 1.3, 2.3, 3.3, and 4.3 dS m(-1)) and four concentrations of hydrogen peroxide (H2O2: 0, 25, 50, and 75 mu M). Each treatment was replicated four times, with two plants per plot. Irrigation with water having an electrical conductivity of 0.3 dS m(-1) significantly inhibited gas exchange, photochemical efficiency, and growth of guava seedlings after 91 days of emergence. Foliar application of hydrogen peroxide at concentrations up to 75 mu M did not alleviate the effects of salt stress during the seedling formation phase of guava plants. Guava cv. Paluma was found to be sensitive to water salinity during the seedling formation phase, with a threshold level of 0.3 dS m(-1) and a decrease in the growth rate of 11.48% per unit increase in salinity.