Physiological and biochemical responses of mini watermelon irrigated with brackish water under two types of irrigation system

Abstract

the use of marginal quality water can be a viable alternative in regions with water scarcity when associated with an adequate irrigation management strategy. The aim of this study was to evaluate the physiological and biochemical responses of ‘Sugar Baby’ mini watermelon as a function of irrigation management and salinity of the nutrient solution (ECsol). The experiment was carried out in a greenhouse of the Federal University of Recôncavo of Bahia, in the municipality of Cruz das Almas - BA, in a completely randomized design, with four replications. The plants were grown under two types of irrigation management (conventional drip - CD and pulse - PD) and four saline levels of the fertigation nutrient solution (2.5 - control; 4.5; 5.5; 6.5 dS m-1). At 65 days after cultivation, the following variables were evaluated: chlorophyll a and b content, chlorophyll a fluorescence, and organic and inorganic solutes content. The treatments did not influence the levels of chlorophyll a and b. Salinity decreased the quantum yield of photochemical energy conversion due to the increased quantum yield of unregulated energy loss. Irrigation management and water salinity did not affect carbohydrate content in mini watermelons leaves. However, soluble proteins were higher in the CD than in PD and decreased with increasing salinity in both managements. Salinity increased free amino acids in CD but did not change the content of these solutes in PD. Free proline was only influenced by the management system and was higher in CD than in PD. Sodium, chloride, and sodium to potassium ratio increased with ECsol, but these increases were more pronounced in PD. Salinity increased potassium content in PD and reduced in CD. The CD led to lower absorption of toxic ions, reducing the effects of salinity on the mini watermelon.