Foliar application of ascorbic acid in guava cultivation under water replacement levels

Abstract

Ascorbic acid is a non-enzymatic compound with antioxidant action in the detoxification of reactive oxygen species in plants subjected to abiotic stress conditions. Therefore, the objective of this study was to evaluate gas exchange, photochemical efficiency, and growth of guava cv. Paluma under water replacement levels and foliar application of ascorbic acid in the post-grafting phase. The experiment was carried out under greenhouse conditions, at the Center of Technology and Natural Resources, at the Federal University of Campina Grande, in Paraíba, PB, Brazil. A randomized block experimental design was used, in a 2 × 4 factorial arrangement, whose treatments resulted from the combination of two factors: two levels of irrigation water (50 and 100% of actual evapotranspiration - ETr) and four concentrations of ascorbic acid - AsA (0, 30, 60, and 90 mM), with three repetitions. Irrigation with a 50% ETr depth reduced the growth in rootstock diameter, scion diameter, and scion volume, as well as gas exchange: stomatal conductance, transpiration, and maximum and variable fluorescence indices of guava cv. Paluma. Ascorbic acid concentration of 90 mM increases the CO2 assimilation rate and instantaneous water use efficiency and reduces electrolyte leakage in the leaf blade of guava plants, 240 days after transplanting.