Induction of Thermotolerance through Heat Acclimation and Phytohormones in Mung Bean Seedlings

Abstract

High temperature is one of the major abiotic stress that can reduce yield of any crop. Plants have different optimum temperature for best morphological and physiological performance and 30°C is optimum temperature for mung bean where as lethal temperature is 50°C. The ultimate aim is  to study the pretreatment effect of moderately high temperature (40°C) and phytohormones [indole acetic acid (IAA) and gibberellic acid (GA₃) prior to heat shock (50°C) to reduce the adverse effects of  heat shock and induction of thermotolerance in mung bean seedlings.  The experimental material consisted of mung bean genotype (NM 13-1), seeds were imbibed in distilled water, 100 µM IAA and 100 µM GA₃ for 20 h, allowed to grow in distilled water for 24 h, then treated with heat shock (50°C for 2h) and pretreated with moderately high temperature (40°C for 1h ) prior to 50°C. Heat shock showed extremely retarded growth, low levels of proteins, ascorbate peroxidase (APX) and catalase (CAT) with increased activity of guaiacol peroxidase (GPX) as compared to control (30°C). In contrast, the moderately high temperature (40°C for 1 h) prior to 50°C observed improved growth and further increase in the activity of APX, CAT and GPX. The growth effect and enzymes activity became more enhancing when seedlings were imbibed in IAA and GA₃ for both control (30°C) as well as treated samples. Protein profile also revealed minor variations among control and treated samples. Pretreatment with moderately high temperature and phytohormone is an easy and effective method for the induction of thermotolerance in mung bean.  

Keywords: Antioxidant enzymes, ascorbate peroxidase, catalase, gibberellic acid, guaiacol peroxidase, heat shock,  indole acetic acid, thermotolerance