Effect of combined potassium-phosphorus fertilization on gas exchange, antioxidant activity and fruit production of West Indian cherry under salt stress

Abstract

Salt stress is abiotic stress that directly affects the gas exchange and redox metabolism of the plants. However, some studies claim that the combination of potassium-phosphorus fertilization may increase salt tolerance in plants. In this context, the objective of this study was to evaluate gas exchange and the antioxidant enzyme activity responses to combined potassium-phosphorus fertilization in the tissues of West Indian cherry during the fructification phase, 240 days after application of treatments (DAT) in the second year of brackish water irrigation production. The treatments were distributed in randomized blocks, in a 5 × 4 factorial scheme, with five levels of irrigation water electrical conductivity – (ECw equal to 0.6 – control, 1.4; 2.2; 3.0 or 3.8 dS m−1) and four potassium-phosphorus fertilization combinations, 200/120; 170/102; 120/72 or 90/54 g K2O/P2O5 plant−1 per year, with three replicates. Irrigation water salinity impaired the gas exchange, showing a reduction of 47.94, 47.21, and 43.92% in the stomatal conductance, transpiration, and CO2 assimilation, respectively. In contrast, it increased the antioxidant metabolism, mainly the catalase enzyme activity (+ 67.7%). The average weight of fruits was increased by 85% in the combination of 90/54 under 1.4 dS m−1. Although the average number of fruits, in same combination (90/54) was 37% lower compared to high salinities. The threshold water salinity (1.12 dS m−1) indicates that West Indian cherry is a salt sensitive crop.