Attenuation of vanillic acid toxicity by foliar application with indole-3-acetic acid in tomato seedlings

Abstract

ABSTRACT The allelopathic compound vanillic acid (VA), a phenol present in tomato (Solanum lycopersicum L.), behaves as a potent autotoxin and hampers growth processes. Indole-3-acetic acid (IAA) regulates growth and metabolism of plants under various environmental extremes. The work was undertaken to determine alleviating effects of IAA (1 mM) on biochemical and physiological responses of tomato plants exposed to VA toxicity (0.5 or 1 mM). Plants were grown under glasshouse conditions, treated with VA by root exposure and IAA through foliar application. The VA restrained plant growth at both doses by reducing pigment content, relative water content, protein content, nitrate reductase activity and anthocyanin content. Increased antioxidant enzyme activity, electrolyte leakage, lipid peroxidation, hydrogen peroxide, proline content and phenylalanine ammonia lyase activity were measured in stressed plants. Foliar application of IAA in plants treated with VA alleviated biophysical and biochemical parameters to promote restoration. The foliar IAA application could protect plant cellular mechanisms against endogenous autotoxins in plants grown in fields under monocropping. The IAA may protect plants exposed to VA toxicity by accelerating defense mechanisms.