BIOCHEMICAL ASPECTS AND CHLOROPHYLL A FLUORESCENCE IN HYDROPONIC MINI WATERMELON PLANTS UNDER SALT STRESS

Abstract

Salinity is one of the main abiotic stresses that induce biochemical and physiological disorders in diverse crops. The objective of this study was to investigate the effects of the nutrient solution salinity (ECsol) on the production, accumulation of organic and inorganic solutes and chlorophyll a fluorescence in mini watermelon plants cv. Sugar Baby. The experimental design was completely randomized with four replications. The plants were grown in a hydroponic system with five levels of ECsol: 2.5; 3.5; 4.5; 5.5 and 6.5 dS m^-1. The variables evaluated were: mass of the fruit, biomass of the aerial parts, contents of chlorophylls a and b, fluorescence of chlorophyll a, and contents of organic and inorganic solutes. The mass of the fruit and the dry biomass of the aerial parts were negatively influenced by ECsol. There was a reduction in the concentration of total soluble carbohydrates, free amino acids, soluble proteins and free proline with the increase in ECsol. The sodium, chloride and sodium/potassium ratio increased with ECsol and potassium levels were reduced. The increase in ECsol linearly increased the chlorophyll b content and reduced the quantum yield of the photochemical energy conversion of the PSII promoting a slight increase in the quantum yield of the regulated energy loss of the PSII.