Cultivo de minimelancia com águas salobras: aspectos fisiológicos, produtivos e qualidade pós-colheita

Abstract

To evaluate the development, physiological, productive aspects and postharvest quality of miniwatermelon in brackish water, four experiments were done. The first experiment evaluated the initial growth of 'Sugar Baby' miniwatermelon through univariate and multivariate statistical techniques, using four electrical conductivities of irrigation water (ECa): 0.33; 1.5; 3.5; 5.5 dS m-1 . Water salinity negatively affected the emergence time of miniwatermelon seedlings, plant height and dry mass. Multivariate analysis allowed for better visualization of the results. The second experiment evaluated the production, quality, and physiological and biochemical responses of 'Sugar Baby' miniwatermelon in substrate using two types of irrigation management (conventional and pulsed drip) and four saline levels of the nutrient solution for fertigation (2.5; 4.5; 5.5 and 6.5 dS m-1 ). Salinity affected some production variables, however it did not affect the quality of 'Sugar Baby' miniwatermelon fruits and conventional dripping was the most suitable for high salinity. The salinity of the water did not compromise the integrity of the miniwatermelon photosynthetic apparatus, however, it does increase the dissipation of unregulated non-photochemical excitation. The sodium and chloride contents and the sodium/potassium ratio in the leaf increased with the water salinity in the pulse management. Salinity increased potassium levels in pulse management and decreased in conventional one. The third experiment evaluated the water relationships, physiology, biochemistry, production, postharvest quality of 'Sugar Baby' miniwatermelon cultivated in a hydroponic system using brackish water in the nutrient solution (2.5; 3.5; 4.5; 5.5; 6.5 dS m-1). The salinity of the nutrient solution negatively affected the fruit mass, cross-sectional circumference and diameter of the miniwatermelon pulp, but did not influence the Brix. Organic solute contents and sodium, chloride ions, sodium/potassium ratio and photochemical energy conversion quantum yield of photosystem II (FSII) were reduced with salinity. Water salinity increased leaf chlorophyll b and potassium content and quantum yield of FSII regulated energy lost. The fourth experiment consisted of evaluating the yield, postharvest quality and solute content of two miniwatermelon genotypes (Champagne and Fancy) cultivated in a hydroponic system using brackish water from nutrient solutions with different electrical conductivities: 2.5; 3.5; 4.5; 5.5; 6.5 dS m-1. Salinity reduced the main productive characteristics of the miniwatermelon, but maintained the post-harvest commercial acceptance standards. The results of organic and inorganic solutes in the leaves showed possible differences regarding the acclimation of the genotypes to salinity.