Ácido salicílico e condutividade elétrica da água de irrigação no crescimento e na fisiologia de mudas do mamoeiro

Abstract

Papaya is considered a crop of great socioeconomic importance in Brazil and worldwide. The Northeast region of Brazil stands out in terms of production, however, the arid and semi-arid regions are characterized by having an excess of salts in the water. Salicylic acid is among the main classes of hormones found in plants, considered a regulator of responses to abiotic stresses, such as salinity. The objective of the research was to evaluate the action of salicylic acid as a mitigation of the effects of electrical conductivity of irrigation water on the growth and physiology of papaya seedlings. The experiment was carried out in a protected environment, in the fruit nursery at the Federal University of Paraíba, in Areia, Paraíba, Brazil. The experiment was carried out in a protected environment, in the fruit nursery at the Federal University of Paraíba, in Areia, Paraíba, Brazil. The experimental design was in randomized blocks, with the treatments obtained according to the Box Central Composite experimental matrix, referring to five electrical conductivities of irrigation water and five doses of salicylic acid, with minimum and maximum values of 0.3 and 5.0 dSm-1 and 0.0 and 2.0 mmol L-1, with three repetitions. Seedlings were evaluated for growth (height, stem diameter, leaf area and dry matter mass), gas exchange, chlorophyll fluorescence and chlorophyll content. There was an interaction of the studied factors for leaf area and stem diameter. In isolation, a significant difference was found for height and shoot dry matter. As for the physiological variables, there was an interaction of the studied factors for initial fluorescence, Fv/Fm ratio, transpiration and stomatal conductance, thus, both factors interfere simultaneously in papaya seedlings. In isolation, the indices of a, b and total chlorophylls, net photosynthesis and maximum fluorescence were significantly influenced for the aforementioned factors, except for net photosynthesis and maximum fluorescence, which were significant only for electrical conductivities of irrigation waters. Salt stress reduces all the studied variables, referring to the growth and physiology of papaya seedlings. Salicylic acid increases Fv/Fm, transpiration and stomatal conductance at the highest values of electrical conductivity of irrigation water.