Phenolic Biosynthesis Inhibitors Accentuate the Effects of Heat-Shock Injury in Mung Bean Seedlings

Abstract

ABSTRACT Germinating seeds of Vigna radiata (Linn) Wilczek cv. ML 311, with a radicle length of 5 mm, were subjected to a brief heat-shock episode of 50°C for 2 h followed by transfer to the normal temperature (28°C) for three days in the dark. Exogenous effects of salicylic acid and two inhibitors of phenylalanine ammonia lyase (PAL), i.e., AOPP (L-a-aminooxy-β-phenyl propionic acid) and AIP [2-(aminoindan-2-phosphonic acid)], applied either as a pre-treatment at the normal temperature (28°C, 2 h) or as a co-treatment during the heat-shock period itself (50°C, 2 h), were studied alone and in combination, with a view to modulate the heat-shock response of etiolated seedlings. Growth analysis revealed that treatment with AOPP and AIP rendered the seedlings more vulnerable to heat shock, whereas co-application of salicylic acid either alone or in combination with PAL inhibitors appreciably enhanced the thermotolerance ability of both roots and hypocotyls in intact seedlings. Enhanced thermotolerance was ass...