Activity of some enzymes in barley caryopses during imbibition in aluminium presence

Peroxidase, superoxide dismutase, acid and alkaline phosphatase, esterase and glucosidase activities were studied during imbibition of barley caryopses in the presence of aluminium. Antioxidative enzymes (peroxidase, superoxid dismutase) showed elevated activity already 2 h after the onset of imbibition in the presence of Al. In contrast hydrolytic enzymes (phosphatases, glucosidase, esterase) were only moderately activated at low Al concentrations (1-2mM), while strong inhibition was observed at higher Al concentrations (4-8mM). In in vitro conditions 8mM Al had no effect on the activity of acid phosphatase, moderately inhibited alkaline phosphatase and glucosidase and strongly esterase activity. During imbibition of caryopses in solution without Al an increase of the pH value of the imbibition solution from 4 to 6 has occurred, while in the presence of Al the shift in pH value was less expressive and dependent on Al concentration. At 8mM Al concentration no change in the pH value of imbibition solution was observed. The SDS-PAGE analysis of polypeptides released to the imbibition solution in the presence of Al revealed the accumulation of two polypeptides with relative molecular mass of 35 and 18 kDa. The release of 96 and 27.5 kDa polypeptides was completely inhibited at 8mM Al concentration. These results confirmed that Al is able to influence different physiological processes already during seed imbibition and early growth phases of barley seedlings.