The objective of this study was to evaluate the effect of a plant growth regulator (PGR; Stimulate®) on the yield and quality of zucchini fruits from plants of the cultivar Caserta-Italiana grown under different salinity levels of the irrigation water (SLIW). A randomized block design was used, in a 2 × 6 factorial arrangement consisted of two SLIW (0.5 and 5.0 dS m-1) and six PGR application modes: imbibition of seeds for 8 h in distilled water (PGR-T1; Control); imbibition of seeds for 8 h in PGR at 10 mL L-1 (PGR-T2); imbibition of seeds for 8 h in PGR at 10 mL L-1 plus foliar application at 10 mL L-1 at the flowering stage (PGR-T3); imbibition of seeds for 8 h in PGR at 10 mL L-1 plus two foliar applications at the flowering stage and at 20 and 30 days after sowing (PGR-T4); foliar application at 10 mL L-1 at the flowering stage (PGR-T5); and two foliar applications at 10 mL L-1 at 20 and 30 days after sowing (PGR-T6). The SLIW affected differently the variables of the zucchini crops evaluated. The PGR application to plants under no salt stress (0.5 dS m-1) increased the solid soluble concentration and biomass accumulation of zucchini fruits. The PGR application as seed treatment and foliar application at the flowering stage increased the fruit yield of zucchini plants irrigated with saline water.

Crops are constantly threatened by salinity. Nitric oxide (NO) is an attenuating agent for salt stress; however, the specific roles of NO in gas exchange and lettuce production are not well established. The objective of this study was to evaluate the application of different concentrations of sodium nitroprusside (SNP) as an agent to mitigate salt stress in lettuce plants. Lettuce seedlings in pots were subjected to irrigation without and with saline water (0.2 and 3.5 dS m⁻¹) and applications of different concentrations (0, 50, 100, 150, and 200 µM) of SNP, a NO donor. Saline stress negatively affected lettuce development with a reduction of 29.5% in leaf area, 6.3% in relative water content in the leaf, 17.2% in stem diameter, and 10.7% in dry matter mass in the control, but the application of SNP mitigated the deleterious effects of salt stress. Concentrations between 100 and 150 µM of SNP improved the photosynthetic metabolism of lettuce under salinity, with an increase of 46.7% in CO₂ assimilation and 42.3% in fresh matter mass. Pearson’s correlation showed that fresh matter correlated positively with CO₂ assimilation. Therefore, SNP can be used to mitigate salt stress in lettuce.

Potassium fertigation may be a strategy to reduce saline stress in okra. The objective of this study was to analyze the effect of potassium supplementation as a salinity-attenuating agent in okra. The experiment was conducted in a greenhouse at the Federal Rural University of the Semi-Arid Region, in Mossoró-RN, Brazil. The experimental design was completely randomized, in 2x5 factorial scheme with 4 replicates. Two okra cultivars (Santa Cruz 47 and Valença) fertigated with five fertigation managements [F1= irrigation with non-saline water (0.55 dS/m) and fertigation with a standard dose of potassium (6 g/plant); F2= irrigation with saline water (3.5 dS/m) and fertigation with 6 g/plant of K, F3= irrigation with saline water (3.5 dS/m) and fertigation with 9 g/plant of K, F4= irrigation with saline water (3.5 dS/m) and fertigation with 12 g/plant of K, and F5= irrigation with saline water (3.5 dS/m) and fertigation with 15 g/plant of K]. Plants were collected 110 days after emergence and evaluated for growth variables (leaf number, leaf area, leaf dry mass, stem dry mass, total dry mass) and yield (fruit number, average fruit mass and fruit production). Potassium influenced the growth and yield characteristics of okra irrigated with saline water. The highest yields of fruits occurred at 9.56 and 10.23 g/plant of K, being 330.24 and 733.36 g/plant obtained from cultivars Santa Cruz 47 and Valença, respectively. Okra irrigated with saline water is more demanding in potassium.

The electrical conductivity of the nutrient solution directly affects production and quality of the plants. We evaluated the electrical conductivity suitable for soilless cultivation of kohlrabi. The experiment was carried out in a completely randomized design, with four replicates and five treatments, composed of different nutrient solution’s conductivities (1.31, 1.71, 2.37, 2.98 and 3.75 dS m-1). We evaluated number of leaves, leaf area, specific leaf area, leaf area ratio, fresh and dry masses of leaves, bulb, roots and total, bulb volume, water content in the bulbs and pH, soluble solids, vitamin C, firmness, titratable acidity and SS/TA ratio of the bulbs. All variables related to growth were affected by the nutrient solutions, showing the highest values with the use of the nutrient solutions with EC close to 2.0 dS m-1. Considering the commercial part of the plant, the most developed bulbs were obtained with EC of 1.96 dS m-1, being 49.9 g and 41.15 cm3 per bulb. On the other hand, except for pH, the other variables responded to the increase of EC. Higher values for pulp firmness and titratable acidity occurred with EC close to 2.0 dS m-1, whereas the other variables showed higher values using a more concentrated nutrient solution.

Water availability is a limiting factor for plant production, especially in Brazilian semi-arid regions. The main aim of the study was to investigate the physiological effects of drought during the fruiting stage of watermelon cultivation. A completely randomized block design with four replications and six treatments varied by the number of lateral drip tapes (1 or 2) and the duration of drought stress (0, 4, and 8 days) was used. The following parameters were evaluated: relative chlorophyll content, relative leaf water content, electrolyte leakage, CO₂ assimilation (A), stomatal conductance (g_s), internal CO₂ concentration, leaf temperature, transpiration (E), water use efficiency (WUE), carboxylation efficiency (CE), yield, thickness, diameter, length, and fruit °brix, at 4 and 8 days of drought. Drought negatively affected photosynthesis, particularly in treatments with a single dripper and 4 days of drought, resulting in reductions of up to 60% in A, 68% in g_s, 44% in E, 58% in WUE, and 59% in CE, but did not have a significant effect on watermelon yield after 4 or 8 days of irrigation. It was concluded that drought influences the physiological responses of watermelon plants, mainly in reducing photosynthesis, but does not drastically affect fruit productivity in short periods of stress.