GAS EXCHANGE AND PRODUCTION OF PASSION FRUIT AS AFFECTED BY CATIONIC NATURE OF IRRIGATION WATER

Abstract

Yellow passion fruit is a fruit species widely cultivated throughout the Brazilian semi-arid territory, but its yield is affected by the quality of the waters of this region. In this context, the objective was to evaluate the gas exchange and production of passion fruit cv. BRS Rubi do Cerrado irrigated with waters of different cationic natures. The study was conducted in drainage lysimeters under greenhouse conditions in Campina Grande, PB, Brazil, in a randomized block design, and the treatments were eight cationic natures of irrigation water (S₁ - Control; S₂ - Na⁺; S₃ - Ca²⁺; S₄ - Mg²⁺; S₅ - Na⁺ + Ca²⁺; S₆ - Na⁺ + Mg²⁺; S₇ - Ca²⁺ + Mg²⁺ and S₈ - Na⁺ + Ca²⁺ + Mg²⁺) with three replicates. Plants in the control treatment were irrigated with water of low electrical conductivity (ECw = 0.4 dS m^-1), while those of the other treatments were irrigated using water with ECw of 3.5 dS m^-1. The treatments Na⁺ + Ca²⁺, Na⁺ + Mg²⁺ and Ca²⁺ + Mg²⁺ were prepared in the equivalent ratio of 1:1, and Na⁺+Ca²⁺+Mg²⁺ in the ratio 7:2:1, respectively. Water salinity of 3.5 dS m^-1 reduced gas exchange, and stomatal conductance and transpiration were the most sensitive variables of passion fruit. The number of fruits of passion fruit cv. BRS Rubi do Cerrado decreased with water salinity, regardless of the cationic nature. The waters of calcic and calcic+magnesian nature caused the greatest deleterious effects on the production variables of passion fruit, at 259 days after transplanting.