Foliar Application of Salicylic Acid Mitigates Saline Stress on Physiology, Production, and Post-Harvest Quality of Hydroponic Japanese Cucumber

Abstract

Salicylic acid (SA) is a phenolic compound capable of inducing physiological and metabolic changes that enhance the tolerance of plants to saline stress associated with using a hydroponic system and enable the use of saline water in semi-arid regions. In this context, this assay aimed to evaluate the impact of the foliar application of SA on mitigating salt stress effects on Japanese cucumber cultivated in a hydroponic system. The experiment was carried out in a protected ambient (greenhouse), using the Nutrient Film Technique—NFT hydroponic system. A completely randomized design was performed in a 4 × 4 split-plot scheme, with four levels of electrical conductivity of the nutrient solution—ECns (2.1, 3.6, 5.1, and 6.6 dS m−1)—considered as plots and four SA concentrations (0, 1.8, 3.6, and 5.4 mM), regarded as subplots, with four replicates and two plants per plot. An increase in the ECns negatively affected the physiology, production components, and post-harvest quality of cucumber. However, the application of SA to leaves at concentrations between 1.4 and 2.0 mM reduced the deleterious effects of saline stress and promoted an increase in the production of and improvement in the post-harvest quality of cucumber fruits.

Foliar Applications of Salicylic Acid on Boosting Salt Stress Tolerance in Sour Passion Fruit in Two Cropping Cycles

“…These results may be related to low efficiency in quinone photoreduction and electron flow between photosystems, which results in low PSII activity in the thylakoid membrane, directly influencing the flow of electrons between photosystems [ 62 , 63 ]. In addition, it may indicate that the photosynthetic apparatus was damaged by salt stress, compromising photosystem II, with negative effects on the photosynthetic process [ 1 ], as observed in this study.…”

“…Despite the deleterious effects of salt stress on RWC and EL, foliar application of salicylic acid in concentrations between 1.0 and 1.2 mM mitigated the effects of irrigation water salinity in the first cropping cycle of sour passion fruit. Salicylic acid acts to protect plant cells from the toxicity caused by ion accumulation and improves antioxidant activity, nitrogen metabolism, and water absorption in plants [ 46 , 47 ], increasing leaf turgor and reducing cell membrane damage [ 1 ].…”

“…In recent years, the availability of fresh water has caused concerns, especially in semi-arid regions [ 1 ]. Climate change that has occurred all over the world has increased atmospheric temperatures and caused droughts [ 2 , 3 ].…”

Hydroponic Cultivation of Laranja Cherry Tomatoes under Salt Stress and Foliar Application of Hydrogen Peroxide

“…Substrate preparation and seedling formation were carried out according to a study carried out by Mendonça et al [17]. The proportion and preparation of salinity levels of the nutrient solution were carried out according to Oliveira et al [11].…”

“…The harmful effects caused by salt stress are related to the reduction in the availability of water and nutrients to plants and to the toxic effect of Na + and Cl − [8,9]. Excess salts present in the water also induce osmotic stress, ionic toxicity, and secondary stress as oxidative stress, directly leading to reductions in fruit production and post-harvest quality [10][11][12].…”