Water stress-induced changes in the levels of ethylene, ACC and ACC-oxidase activity in French bean

Changes in leaf relative water content (RWC), ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) and ACC-oxidase activity were studied in two cultivars of French bean, IIHR-909 (susceptible) and Contender (tolerant) subjected to varied durations of water stress at vegetative and flowering stages. Water stress treatment (4 & 8 day) increased ethylene production, ACC content and ACC-oxidase activity while longer stress duration (10 & 12 day) declined these parameters in both the cultivars, with cv. IIHR-909 showing greater changes. The leaf RWC with stress registered progressive decline in both the cultivars. The water stress induced ethylene production under short stress durations is attributed to accelerated rate of ACC accumulation and enhanced ACC-oxidase activity. The similarity in the trends of leaf ethylene production and ACC levels under stress and their inconsistency with stress severity reveal that these may not be good indicators of stress tolerance.