Atenuação de estresse híbrida em plantas de feijão-caupi tratadas com ácido salicílico

Abstract

Cowpea is a one of the legume most consumed in the North and Northeast of Brazil, being a major component of the population diet. In the critical stages, the severity of drought is one of the factors that limit the plant growth. However studies have reported that effects of drought on the plant can be mitigated through the application of endogenous elicitors such as salicylic acid (SA). Thus, the objective of this work was to evaluate cowpea genotypes subjected to drought with salicylic acid applications. The research consisted of a 2x2x5 factorial, two cowpea genotypes (BRS Paraguaçu and Pingo de Ouro 1-2), two irrigation levels (one befitting to soil moisture near field capacity, 10 and 15 kPa, and another in a condition of stress (60 to 80kPa) and five concentrations of salicylic acid (zero; 0.1; 0.5; 1.0; 2.0 mM) applied 15 days after sowing each three days during six days. The combination of these factors resulted in 20 treatments, arranged in a completely randomized design with three replications, and the experimental plot consisted of 3 working vessels initially containing 6 plants. Growth evaluations ( plant height, leaf number, stem diameter and dry mass of shoots), physiological assessments (photosynthesis, stomatal conductance, transpiration, leaf water potential and intrinsic efficiency in water use), biochemical (activities of peroxidase ascorbate - APX, catalase - CAT, superoxide dismutase - SOD and free proline content) and production (long pods, weight of pods, number of grains per pod, grain diameter, 100 seed weight, moisture content and productivity) were analyzed. The application of 1.0 mM SA provided benefits to physiological parameters in both genotypes at both conditions. The activity of antioxidant enzymes increases in water drought conditions, but no responded to foliar application of salicylic acid. Although not significant, the proline accumulation in drought conditions increased the tolerance in Pingo Gold-1-2. Pingo de Ouro 1-2 had lower productivity, but increased tolerance to drought. In the vegetative phase, the foliar application of salicylic acid attenuates water deficit in cowpea. tolerância ao déficit. Pingo de Ouro-1-2 obteve menor produtividade, porém uma maior tolerância ao déficit hídrico. A aplicação foliar do ácido salicílico na fase vegetativa atenua o déficit hídrico moderado em feijão-caupi.