Effect of saline stress, and nitrogen and potassium fertilization on morphophysiology of <i>Passiflora edulis</i> Sims. f. <i>flavicarpa</i> Dreg.

Abstract

In Brazil semi-arid regions, excess of soluble salts is a limiting factor for the success of agricultural crops. An adequate supply of nutrients can cause positive responses in plant species under salt stress. The objective of this study was to analyze the effect of nitrogen and potassium on the morphophysiology of passion fruit (Passiflora edulis) seedlings subjected to saline stress. The design was a randomized blocks design, with treatments generated by the Box Central Composite Design matrix. Five electrical conductivities of irrigation water (ECw = 0.5, 0.98, 2.15, 3.32, and 3.80 dS m^-1), five doses of nitrogen (N) and potassium (K) (0.0, 29.08, 100.0, 170.92, and 200.0%), in four replications. The combination of 200% NK stimulated the synthesis of chlorophyll a, and total chlorophyll under low salinity conditions (0.5 dS m^-1). The chlorophyll a/b ratio was higher at ECw of 3.8 dS m^-1 and under a concentration of 20.23% NK. The increase in water salinity from of 0.5 dS m^-1 caused deleterious effects on the growth of passion fruit seedlings. The doses of NK between 100% and 120% improved the absolute growth rates of plant height and stem diameter, chlorophyll b, aerial dry matter, and total dry matter. The 200% dose of NK improved the leaf mass ratio. The combination of N and K applied foliar proved to be efficient in reducing the effects of salinity on the synthesis of photosynthetic pigments, providing better growth conditions for yellow passion fruit seedlings.