Given the quantitative scarcity of low-salinity water resources in the Brazilian semi-arid region, it is necessary to use water with a high concentration of salts. Thus, identifying salt-stress tolerant cultivars of crops is an alternative for expanding irrigated agriculture. The objective of this study was to evaluate the tolerance of passion fruit cultivars as a function of irrigation water electrical conductivity. The experimental design was randomized blocks, in a 5 × 3 factorial scheme, whose treatments consisted of the combination of five values of electrical conductivity of irrigation water - ECw (0.3, 1.1, 1.9, 2.7, and 3.5 dS m^-1) and three sour passion fruit cultivars (BRS GA1, BRS SC1, and SCS437, with three replicates. Electrical conductivity of water from 0.3 dS m^-1 reduces the relative water content, gas exchange, and the number of fruits and increased electrolyte leakage in the leaf blade of passion fruit plants, at 153 days after transplantation. The passion fruit cultivars BRS GA1, BRS SC1, and SCS437 were classified as sensitive, with threshold electrical conductivity of water of 0.3, 1.0, and 0.3 dS m^-1, respectively.

The objective of this study was to evaluate the physiology and growth of guava cv. Paluma as a function of irrigation with saline water and foliar application of ascorbic acid. The study was conducted using a randomized block experimental design in a 5 × 4 factorial scheme, whose treatments were formed by combining five levels of electrical conductivity of irrigation water - ECw (0.3, 1.2, 1.9, 2.6, and 3.3 dS m^-1), associated with four concentrations of ascorbic acid - AsA (0, 30, 60, and 90 mM), with three replicates and one plant per plot. Stem diameter, crown volume, vegetative vigor index, photosynthetic pigment contents, photochemical efficiency, electrolyte leakage, and relative water content were evaluated. Ascorbic acid at concentration of 60 mM increased electrolyte leakage and relative water content in plants under ECw of 3.2 and 2.9 dS m^-1, respectively. AsA concentration of 90 mM stimulated the biosynthesis of chlorophyll a, chlorophyll b, and total chlorophyll of guava plants grown under water salinity of 3.3 dS m^-1. Salinity above 0.3 dS m^-1 reduced chlorophyll a fluorescence, crown volume, and vegetative vigor index of guava. Foliar application of 30 mM ascorbic acid increased the quantum efficiency of photosystem II up to ECw of 2.5 dS m^-1. The beneficial effect of ascorbic acid was obtained under ECw of 0.3 dS m^-1.

Fruit growing is an activity of great relevance for agribusiness in Brazil, with emphasis on guava. However, water deficiency is one of the limiting factors for plant productivity, so the use of phytohormones such as salicylic acid has been employed as a strategy to mitigate the effects of water deficit. The objective of this study was to evaluate the foliar application of salicylic acid as an attenuator of water deficit in guava genetic materials. The experimental design adopted was randomized blocks, in a 2 × 2 × 5 factorial scheme, considering two water regimes (irrigation depths equivalent to 50 and 100% of the reference evapotranspiration - ETr), two guava genetic materials (‘Crioula’ and ‘Paluma’) and five concentrations of salicylic acid (0, 1.2, 2.4, 3.6, and 4.8 mM). Foliar application of salicylic acid at a concentration of 2.4 mM promoted growth, gas exchange, and chlorophyll a fluorescence of ‘Crioula’ guava under irrigation with 50% ETr. Water deficit reduced growth, gas exchange, chlorophyll contents, and chlorophyll a fluorescence of guava. Among the genetic materials, greater growth, gas exchange, chlorophyll contents, and chlorophyll a fluorescence was observed in ‘Paluma’ compared to ‘Crioula’ under irrigation with 50% ETr without foliar application of salicylic acid. Foliar application of salicylic acid at a concentration of 1.2 mM increases leaf area, number of leaves, and total dry mass in the ‘Crioula’ genetic material under 50% ETr.

The objective of this study was to evaluate the physiology and production of sugar-apple as a function of irrigation intervals and foliar application of proline under the conditions of Paraíba’s semi-arid region. A randomized block design was laid out in a 4 × 2 factorial scheme, with treatments resulting from the combination of four irrigation intervals (1, 4, 8 and 12 days) and two concentrations of proline (0 and 10 mM), with four replicates, and the plot consisted of four usable plants. Increase in irrigation intervals reduced the gas exchange of sugar-apple plants at 298 days after transplanting. Exogenous application of proline at concentration of 10 mM increased contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids and fruit fresh mass in plants grown under 12-day irrigation intervals.

This study evaluated the effects of reduced glutathione (GSH) application on the production and quality of sour passion fruit irrigated with brackish water in the semi-arid region of Paraíba, Brazil. The experiment was conducted in drainage lysimeters under greenhouse conditions at the Center of Technology and Natural Resources of the Federal University of Campina Grande (UFCG). Treatments combined five levels of electrical conductivity of brackish irrigation water (Bw: 0.4, 1.2, 2.0, 2.8, and 3.6 dS m⁻¹) and four GSH concentrations (0, 40, 80, and 120 mg L⁻¹), arranged in a randomized block design with three replicates. Salinity levels above 0.4 dS m⁻¹ negatively affected fruit production and post-harvest quality of ‘BRS GA1’ sour passion fruit. Foliar application of 120 mg L⁻¹ GSH increased fruit yield, while 74 mg L⁻¹ GSH mitigated salt stress effects on production and pulp chemical quality. The ‘BRS GA1’ cultivar was highly sensitive to salinity, showing a 26.9% yield reduction per unit increase in Bw electrical conductivity above 0.4 dS m⁻¹. The results suggest that GSH can alleviate salt stress damage, improving crop productivity and fruit quality under semi-arid conditions.

The objective of this study was to evaluate gas exchange, biomass, and quality of guava seedlings as a function of the cationic nature of the water used in irrigation and foliar application of salicylic acid. The experiment was carried out in a greenhouse in Pombal, PB, Brazil, using a randomized block design, in a 6 × 4 factorial scheme with six cationic compositions of irrigation water [S1 - Control (supply water); S2 - Na⁺; S3 - Ca²⁺; S4 - Na⁺+Ca²⁺; S5 - Mg²⁺, and S6 - Na⁺+Ca²⁺+Mg²⁺], associated with four concentrations of salicylic acid (0, 1.3, 2.6, and 3.9 mM), with 3 replicates. Plants in control (S1) were irrigated with water of electrical conductivity (ECw) of 0.3 dS m^-1, while in the other treatments were irrigated with different types of water and had an ECw of 4.3 dS m^-1, consisting of different cations, in the form of chloride. In the seedling formation phase, guava plants were sensitive to calcic water, which resulted in a marked decrease in their growth. Stomatal conductance, transpiration, and biomass accumulation of guava seedlings were more affected by variation in electrical conductivity than by cationic nature of the water. Salicylic acid at concentrations of 2.9 and 1.9 mM increased stomatal conductance and stem dry biomass, respectively, of guava seedlings. Water with ECw of 4.3 dS m^-1 allowed the formation of guava seedlings with acceptable quality for transplanting to the field, regardless of the cationic nature of the water.