Soluções nutritivas salobras e aplicação foliar de ácido ascórbico no cultivo de tomate-cereja em sistema hidropônico com substrato.

Abstract

In the Brazilian semiarid region, due to the use of water sources with high salt content, plants are constantly exposed to saline stress conditions. Therefore, it is extremely important to identify strategies capable of mitigating the deleterious effects of saline stress on plants, among which the foliar application of ascorbic acid stands out. The objective of this study was to evaluate the effect of foliar application of ascorbic acid on the physiological indices, growth, production and postharvest quality of ‘Laranja’ cherry tomatoes grown in brackish nutrient solutions in a hydroponic system with substrate. The research was conducted under greenhouse conditions at the Federal University of Campina Grande, Campina Grande Campus, Paraíba, using a randomized block design in a 5 × 5 factorial scheme, corresponding to five levels of electrical conductivity of the nutrient solution - ECsn (2.1-Control; 2.8; 3.5; 4.2 and 4.9 dS m-1) and five concentrations of ascorbic acid - AsA (0; 150; 300; 450 and 600 mg L-1) with 4 replicates. According to the results, the electrical conductivities of the nutrient solutions from 2.1 dS m-1 negatively affected the physiological indices, growth, production components and phenolic compounds of the cherry tomato plant ‘Laranja’. However, in relation to the other treatments, the foliar application of ascorbic acid at a concentration of 600 mg L-1 associated with the nutrient solution with EC of 2.1 dS m-1 increased the stomatal conductance, transpiration, CO2 assimilation rate, variable fluorescence, leaf area, plant height and number of leaves of the cherry tomato ‘Laranja’. The brackish nutrient solution with ECsn of 4.9 dS m-1 plus the application of AsA at a concentration of 600 mg L-1 increased the parameters of firmness, total soluble solids and total titratable acidity. AsA at a concentration of 600 mg L-1 increased the instantaneous efficiency in water use, the instantaneous efficiency of carboxylation, maximum fluorescence and the synthesis of chlorophylls a and b. The ECsn of 4.9 dS m-1 increased the contents of ascorbic acid, flavonoids and anthocyanins.