Aspectos morfofisiológicos, bioquímicos, produção e pós-colheita de aceroleira sob estresse salino e combinações de adubação com npk

Abstract

The use of saline waters in the cultivation of West Indian cherry (Malpighia emarginata) in the semiarid region of Northeastern Brazil can be made viable through fertilization management, targeting to minimize the damage caused by saline stress. In this context, the objective was to evaluate the effect of fertilization with combinations of nitrogen, phosphorus and potassium as an attenuator of saline stress, on growth, morphophysiology, enzymatic activity, harvest and post-harvest in West Indian cherry, during the second year of production. The study was conducted in a randomized block design, in 2 x 10 factorial scheme, with two levels of electrical conductivity of irrigation water - ECw (0.6 and 4.0 dS m-1), and ten combinations of nitrogen fertilization (N), phosphorus (P2O5) and potassium (K2O) fertilization: (80-100-100; 100-100 100; 120-100-100; 140-100-100; 100-80-100; 100-120-100; 100-140-100; 100-100-80; 100 100-120; 100-100-140% N-P2O5-K2O), with three repetitions. The growth of new branches of West Indian cherry cv. Flor Branca, leaf water status, electrolyte leakage, gas exchange, photosynthetic pigment content, chlorophyll fluorescence, organic and inorganic solutes, enzymatic activity, production, and post-harvest were evaluated. An interaction was verified between the electrical conductivity levels of irrigation water and the fertilizer combinations for relative water content, internal CO2 concentration, CO2 assimilation rate, initial fluorescence, maximum fluorescence, free amino acids, free proline, activity of superoxide dismutase, catalase, ascorbate peroxidase, total number of fruits, total fruit weight, average fruit weight, total titratable acidity, hydrogen potential, total soluble solids, maturation index ratio, vitamin C, reducing sugars, phenolic compounds, flavonoids, and anthocyanins. In isolation, saline levels affected the relative water content, the percentage of electrolyte leakage, internal CO2 concentration, stomatal conductance, transpiration, CO2 assimilation rate, instantaneous carboxylation efficiency, instantaneous water use efficiency, photosynthetic pigments, chlorophyll fluorescence, soluble proteins, free amino acids, activity of superoxide dismutase, catalase, ascorbate peroxidase, total number of fruits, total fruit weight, average fruit weight, equatorial diameter of fruits, total titratable acidity, hydrogen potential, total soluble solids, maturation index ratio, vitamin C, reducing sugars and flavonoids. The irrigation with the higher ECw (4.0 dS m-1) compromised the leaf water status, the leakage of electrolytes from the leaf blade, leaf gas exchange, the content of photosynthetic pigments, the quantum yield of the photosystem II, the growth of new branches and, consequently, affecting all West Indian cherry production variables, at 120 days after pruning, during the second year of production. The enzymatic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) increased when subjected to salt stress (ECw of 4.0 dS m-1). The combination of CA5 fertilizer = 100-80-100% of NPK recommendation (200, 24 and 80 g of NPK per plant) for the second year of production modulates the enzymatic activity of SOD and APX, which mitigates the impacts of salinity in the West Indian cherry, being an efficient choice to preserve its redox homeostasis under saline stress.