Fisiologia e produção do meloeiro sob soluções nutritivas salinas e ácido salicílico.

Abstract

High levels of salinity can cause oxidative stress in plants, limiting growth and productivity in semi-arid regions, mainly due to climatic conditions, such as the Brazilian Northeast. In this context, salicylic acid can minimize the effect of salts, improving the absorption of plant nutrients. The aim was to evaluate the effect of salicylic acid concentrations in mitigating salt stress on the physiology and production of melons grown in a Laminar Nutrient Flow Technique hydroponic system. The experiment was carried out in a greenhouse in Pombal - PB, with a completely randomized experimental design, in a 4 × 4 factorial scheme, with four levels of electrical conductivity of the nutrient solution - CEsn (2.1 - control; 3.2; 4.3 and 5.4 dS m-1), and four concentrations of salicylic acid - AS (0; 1.5; 3.0 and 4.5 mM) applied via foliar, with 6 repetitions. The NEC of up to 4.3 dS m-1 resulted in an increase in maximum and variable fluorescence. Salicylic acid at a concentration of 4.5 mM led to an increase in CO2 assimilation rate and instantaneous water use efficiency. Salicylic acid stimulates total chlorophyll synthesis, CO2 assimilation rate and instantaneous water use efficiency in hydroponic melons. Excess salts in the nutrient solution reduce net photosynthesis, instantaneous carboxylation efficiency and chlorophyll b.