Salicylic acid concentrations and forms of application mitigate water stress in sour passion fruit seedlings.

The present study aimed to evaluate concentrations and forms of application of salicylic acid used for water stress mitigation on the gas exchange and growth of yellow passion fruit. The experimental design was arranged in randomized blocks in a 4 × 4 × 2 factorial scheme, with four concentrations of salicylic acid (SA) via foliar application (0.0, 0.7, 1.4, and 2.1 mM), four SA concentrations via fertigation (0.0, 0.7, 1.4, and 2.1 mM), and two irrigation depths estimated based on the actual evapotranspiration - ETr (50 and 100% of ETr), with three replications. Water stress negatively affected the physiology and growth of yellow passion fruit seedlings at 75 days after sowing (DAS). The application of salicylic acid, regardless of the form of application, attenuates the effects of water stress on gas exchange and growth of yellow passion fruit, with the best results obtained when applying a concentration of 1.30 mM via leaf or 0.90 mM via fertirrigation. The combination of foliar application of AS and fertigation contributed to improve photosynthetic and growth parameters under water conditions of 50 and 100% of ETr. The foliar application of AS presents superior responses to the application via fertigation. These results reinforce the hypothesis that the attenuation of water stress by salicylic acid is related to the maintenance of gas exchange, which depends on the concentration and form of application, and studies testing combinations throughout the crop cycle become promising for advances in knowledge from the action of this phytohormone on abiotic stress.

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.

Physiology and production of sugar-apple under water stress and application of proline.

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.

Irrigation with saline water in the cultivation of mini watermelon under phosphate fertilization.

The objective of this study was to evaluate the water status, photosynthetic pigments, and photochemical efficiency of mini watermelon plants under salt stress and phosphate fertilization. The experiment was conducted in pots under greenhouse conditions in Pombal, PB, Brazil. The experimental design used was randomized blocks in a 5 × 4 factorial scheme, with five levels of electrical conductivity of irrigation water - ECw (0.3, 1.3, 2.3, 3.3, and 4.3 dS m-1) and four doses of phosphorus (60, 80, 100, and 120% of the recommendation), with three replicates. The relative water content in the tissues decreased with the increase in ECw levels in all phosphorus doses, with decreases of 7.05, 7.81 and 8.83% per unit increase in ECw, in plants fertilized with 80, 100 and 120% P2O5. On the other hand, ECw levels increased electrolyte leakage, regardless of phosphorus doses of the recommendation. The synthesis of photosynthetic pigments and the quantum efficiency of photosystem II were inhibited by increasing water salinity from 0.3 dS m-1 in plants grown under phosphorus doses above 60% of the recommendation. Water salinity from 0.3 dS m-1 reduced chlorophyll b contents, initial, maximum, and variable fluorescence of mini watermelon plants, with a decrease of 11.86, 4.51, 4.53, and 4.54% per unit increment of ECw, respectively.

Salicylic acid does not relieve salt stress on gas exchange, chlorophyll fluorescence, and hydroponic melon growth.

The objective of this study was to evaluate the salicylic acid applications in attenuating the harmful effects of saline nutrient solution on the physiology and growth of 'Gaúcho' melon cultivated in the NFT hydroponic system. The experiment was conducted in a greenhouse, in Pombal-PB, Brazil. The cultivation system used was the Nutrient Film Technique - NFT hydroponics. A completely randomized split-plot design was used, with the plot referring to four levels of salinity in the nutrient solution - ECns (2.1 control, 3.2, 4.3, and 5.4 dS m-1) and the sub-plot four concentrations of salicylic acid (SA) (0, 1.5, 3.0, and 4.5 mM), applied via foliar spray, with six replications. Nutrient solution of 4.3 and 5.4 dS m-1 electrical conductivity promotes higher maximum and variable fluorescence, respectively. The stomatal conductance, transpiration, stem diameter, main branch length, leaf dry mass, and stem dry mass of 'Gaúcho' melon plants decrease with the increase in salinity of the nutrient solution. Salicylic acid increases the initial fluorescence and the main branch length of 'Gaúcho' melon plants in hydroponic cultivation. Salicylic acid at a concentration of 1.5 to 4.5 mM did not attenuate the effects of salt stress on the internal CO2 concentration, CO2 assimilation rate, and root dry mass of 'Gaúcho' melon plants.

Morphology of 'Crioula' guava seedlings under irrigation with increasing salinity water and nitrogen/potassium fertilization.

Several studies have been conducted evaluating the management of fertilizers as strategies to mitigate the deleterious effects of salt stress, so the objective of this work was to evaluate the quality of 'Crioula' guava seedlings under irrigation with water of different salinity levels and fertilized with combinations of nitrogen and potassium. The experiment was performed in a protected (screened) environment using a randomized block design and analyzed in a 5 × 4 factorial scheme, with four replicates, with the plot formed by two plants. The treatments were formed from the combination of the factor electrical conductivity of irrigation water (ECw 0.3, 1.1, 1.9, 2.7 and 3.5 dS m-1), with the factor combinations (C) of nitrogen (N) and potassium (K2O) doses, being C1 = 70% N + 50% K2O, C2 = 100% N + 75% K2O, C3= 130% N + 100% K2O and C4= 160% N + 125% K2O. The recommended dose of 100% N and K, respectively, was 541.1 mg N dm-3 soil and 798.6 mg K dm-3 soil. The combinations of N and K fertilization corresponding to 70% N + 50% K2O and 100% N + 75% K2O of the recommended doses promoted greater growth of 'Crioula' guava seedlings. Water with ECw of 2.1 dS m-1 promotes the formation of quality 'Crioula' guava seedlings.

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.

Methods of application of salicylic acid as attenuator of salt stress in cherry tomato.

Salt stress caused by excess salts present in irrigation water, is one of the biggest barriers in agricultural production, especially in semi-arid regions. Thus, the use of substances, such as salicylic acid, that minimize the deleterious effects of salinity on plants can be an alternative to ensure satisfactory production. In this context, the objective of this study was to evaluate the effects of different methods of application of salicylic acid on the growth, production and water use efficiency of cherry tomato plants under salt stress. The study was conducted in a greenhouse, using an Entisol soil with a sandy loam texture. The treatments were distributed in a completely randomized design, in a 2×4 factorial arrangement, corresponding to two levels of electrical conductivity of irrigation water - ECw (0.6 and 2.6 dS m-1) and four methods of application of salicylic acid (Control - without application of SA; via spraying; via irrigation and via spraying and irrigation), with five replicates and one plant per plot. The salicylic acid concentration used in the different methods was 1.0 mM. Application of salicylic acid via foliar spraying increased the growth, production and water use efficiency of cherry tomato plants. The salt stress induced by the electrical conductivity of 2.6 dS m-1 was attenuated by the foliar application of salicylic acid. The use of water of 2.6 dS m-1 associated with the application of salicylic acid via irrigation water further intensified the adverse effects of salinity on cherry tomato plants.

Salicylic acid does not mitigate salt stress on the morphophysiology and production of hydroponic melon.

The excess of salts present in the water can limit the hydroponic cultivation of melon in semi-arid regions of the Brazilian Northeast, making it necessary to use strategies that allow the use of these waters. Among these strategies, the use of elicitor substances stands out, such as salicylic acid. In this context, this study aimed to evaluate the effect of foliar application of salicylic acid in mitigating the harmful effects of salt stress on the morphophysiology and production of 'Gaúcho' melon cultivated in a hydroponic system. A completely randomized design was adopted in a split-plot scheme, with four levels of electrical conductivity of the nutrient solution - ECsn (2.1, 3.2, 4.3, and 5.4 dS m-1) considered the plots and four salicylic acid concentrations - SA (0, 1.5, 3.0, and 4.5 mM), the subplots, with six replications. The foliar application of salicylic acid concentrations did not mitigate the deleterious effects of salt stress on the morphophysiology and yield of melon grown in hydroponic system. The concentration of 4.5 mM of salicylic acid intensified the harmful effects of the salinity of the nutrient solution on gas exchange and fresh weight of hydroponic melon.