Ecofisiologia de cajueiro anão precoce sob estresse salino e ácido salicílico na fase pós-enxertia.

Abstract

Irrigation water salinity may restrict cashew production in the Brazilian semi-arid region. However, the adoption of cultivation strategies, such as the application of salicylic acid, can guarantee the development of irrigated agriculture. In this context, the objective of this research was to evaluate the effect of applying salicylic acid, via the leaves, as a mitigating factor for saline stress on growth and physiology of early dwarf cashew trees in the post-grafting phase. The experimental design was in randomized blocks, in a 5 × 4 factorial arrangement, with five levels of electrical conductivity of irrigation water - ECw (0.4; 1.2; 2.0; 2.8 and 3.6 dS m-1) and four concentrations of salicylic acid (0, 1, 2 and 3 mM) with three replications, totaling 60 experimental units. Irrigation with water with an electrical conductivity above 0.4 dS m-1 negatively affected the relative water content in the leaf blade, leaf gas exchange, photosynthetic pigments and growth of plants that did not receive salicylic acid. However, salicylic acid at a concentration of 1.0 mM attenuated the effects of salt stress on electrolyte leakage, relative water content, gas exchange, photosynthetic pigment synthesis and growth of early dwarf cashew trees under ECw of up to 3.6 dS m-1. Water salinity above 0.4 dS m-1 decreased maximum and variable fluorescence and photosystem II quantum efficiency and increased initial cashew fluorescence at 280 days after transplanting. Precocious dwarf cashew plants cultivated with 0.8 dS m-1 water and 1.0 mM salicylic acid foliar application, obtained greater relative growth in rootstock and scion diameter in the period of 220-280 days after transplant.