Hydrogen peroxide is involved in abscisic acid-induced adventitious rooting in cucumber (Cucumis sativus L.) under drought stress

Abscisic acid (ABA) and hydrogen peroxide (H2O2) are important regulatory factors involved in plant development under adversity stress. Here, the involvement of H2O2 in ABA-induced adventitious root formation in cucumber (Cucumis sativus L.) under drought stress was determined. The results indicated that exogenous ABA or H2O2 promoted adventitious rooting under drought stress, with a maximal biological response at 0.5 mu M ABA or 800 mu M H2O2. The promotive effects of ABA-induced adventitious rooting under drought stress were suppressed by CAT or DPI, suggesting that endogenous H2O2 might be involved in ABA-induced adventitious rooting. ABA increased relative water content (RWC), leaf chlorophyll content, chlorophyll fluorescence parameters (Fv/Fm, I broken vertical bar PS II and qP), water soluble carbohydrate (WSC) and soluble protein content, and peroxidase (POD), polyphenol oxidase (PPO) and indoleacetate oxidase (IAAO) activities, while decreasing transpiration rate. However, the effects of ABA were inhibited by H2O2 scavenger CAT. Therefore, H2O2 may be involved in ABA-induced adventitious root development under drought stress by stimulating water and chlorophyll content, chlorophyll fluorescence, carbohydrate and nitrogen content, as well as some enzyme activities.