ABA application to maize hybrids contrasting for drought tolerance: changes in water parameters and in antioxidant enzyme activity

The objective of this study was to evaluate the effects of abscisic acid (ABA) related to the increase of water-stress tolerance in two drought contrasting maize hybrids: DKB 390 (tolerant) and BRS 1030 (sensitive). The characterization of water status (pre-dawn leaf water potential, I-pd; midday leaf water potential, I-md and stem water potential, I-st) and antioxidant enzyme activity was conducted on greenhouse grown plants. The ABA, hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents were also analyzed. Water deficit was imposed for 10 days at the flowering stage and a dosage of 100 mu M ABA was applied to plant canopy. Measurements were taken during 10 days after the water recovery. With 5 days of stress, the tolerant hybrid showed lower MDA content, decrease in the water status, and higher activity of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, as well as guaiacol, glutathione reductase, dehydroascorbate reductase, polyphenol oxidase, and l-phenylalanine ammonia-lyase, as compared to the sensitive hybrid. With 10 days of stress, DKB 390 had a decrease in the activity of enzymes whereas BRS 1030 showed a higher activity. In addition, the latter showed greater amounts of H2O2 and MDA. ABA application led to a higher tolerance only in DKB 390, due to the increase of water status and the enzymatic activity, mainly the catalase.