Mineral composition and production of guava under salt stress and salicylic acid.

The limitation in the quality of water sources for irrigation in the semi-arid region of northeastern Brazil is increasingly present, so it is necessary to use water with high concentrations of salts for agricultural production, which makes the use of elicitors essential to mitigate the harmful effects of salinity on plants. Given the above, the objective of this study was to evaluate the effects of foliar application of salicylic acid on the mineral composition and production of guava plants under salt stress conditions in the post-grafting phase. The experiment was carried out under greenhouse conditions, in a randomized block design, in a 2 × 4 factorial scheme, with two levels of electrical conductivity of irrigation water (0.6 and 3.2 dS m-1) and four concentrations of salicylic acid (0, 1.2, 2.4, and 3.6 mM), with three replicates. During the flowering stage of guava, N, P, and K contents accumulated in the leaves according to the following order of concentration: N > K > P. Foliar application of 1.2 mM of salicylic acid increases the leaf contents of N, P, and K in guava plants grown under irrigation with water of 0.6 dS m-1. Water salinity of 3.2 dS m-1 reduces the growth and production components of guava plants.

Morphophysiology and production of bell pepper grown under salt stress and salicylic acid foliar application.

Considering the relevance of bell pepper and the limitations imposed by the deleterious effects of salt stress, especially in semi-arid regions, it is extremely important to establish strategies that can facilitate the use of saline water in vegetable production. In this scenario, this study aimed to evaluate the effect of the frequency of foliar application of salicylic acid on the morphophysiology and production of the bell pepper cv. "All Big" irrigated with saline water. The study was conducted at a greenhouse in Campina Grande - PB. The treatments were distributed in a completely randomized design and set up in a 4 × 4 factorial arrangement with three replications, corresponding to four application frequencies of salicylic acid (F1- No application of salicylic acid, F2 - Weekly application, F3- fortnightly application, and F4- monthly application) and four levels of electrical conductivity of irrigation water - ECw (0.8, 1.6, 2.4 and 3.2 dS m-1). The fortnightly application of salicylic acid at a concentration of 1.0 mM mitigated the effects of salt stress on the morphophysiology and production components of bell pepper cv. All Big cultivated with ECw of up to 2.4 dS m-1, which reinforces the hypothesis that salicylic acid can act as a signaling molecule and reduce the effects of saline stress in bell pepper, enabling the use of brackish water in agricultural activity, mainly in semi-arid regions of northeastern Brazil, which have a shortage of fresh water.

Hydrogen peroxide in attenuation of salt stress effects on physiological indicators and growth of soursop.

To mitigate the deleterious effects of salt stress, substances capable of acting as mitigators and/or inducers of tolerance to stress have been used, enabling the use of saline waters and contributing to the development of irrigated agriculture. In this context, the aim of the present study was to evaluate the effect of foliar spraying with hydrogen peroxide as an attenuator of salt stress effects on soursop morphophysiology. The experiment was conducted under greenhouse conditions in Campina Grande - PB, Brazil, using a randomized block design, in a 4 × 4 factorial arrangement, whose treatments resulted from the combination of four levels of electrical conductivity of irrigation water - ECw (0.8 - control, 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. Foliar application of hydrogen peroxide at a concentration of 10 µM increased growth, chlorophyll synthesis, and relative water content in the leaves and consequently reduced the foliar water saturation deficit of soursop irrigated with ECw up to 1.6 dS m-1. The concentration of hydrogen peroxide of 30 µM intensified the salt stress on the electrolyte leakage in the leaf blade and the photosynthetic pigments of soursop, 270 days after transplanting.