Gaseous exchanges, photosynthetic pigments, and growth of mini-watermelons under saline stress and biostimulant treatment

Abstract

High concentrations of dissolved salts in irrigation water represent one of the main challenges for agricultural production in the semi-arid region of Northeast Brazil. To mitigate the harmful effects of salt stress on plants, it is crucial to adopt efficient strategies, particularly the foliar application of biostimulants. In this context, the objective was to evaluate the effect of foliar application of Ascophyllum nodosum L. algae extract on gas exchange, photosynthetic pigments and growth of mini-watermelon cv. Sugar Baby under irrigation with brackish waters under greenhouse conditions, in Campina Grande – PB. The experimental design was randomized blocks in a 5 × 4 factorial scheme with five levels of electrical conductivity of irrigation water – CEa (0.4 control; 1.2; 2.0; 2.8 and 3.6 dS m^-1) and four concentrations of biostimulant based on Ascophyllum nodosum L. algae (0 control; 1.0; 1.5; 2.0 g L^-1), with three replications. Water salinity above 0.4 dS m^-1 reduced the relative water content in the leaf blade, the synthesis of photosynthetic pigments, gas exchange and growth and increased the extravasation of electrolytes in the leaf blade of mini plants. watermelon. Biostimulant concentrations varying from 0.9 and 1.0 g L^-1 increased growth in leaf area and internal CO₂ concentration.