EFFECT OF AGING ON OXYGEN RADICAL GENERATION BY SOYBEAN SEEDS

Rates of leakage of protein and electrolytes were measured in soybean embryonic axes from soybean seeds stored for 8-42 months. A significan t increase in the content of proteins and electrolytes was determined in the external medium where aged embryonic axes were incubated. Lipid peroxidation was evaluated by the measurement of thiobarbituric acid- reactive substances (TBARS) in isolated axes from aged seeds. No signi ficant differences were detected either in the content in vivo nor in the rate of generation in vitro. To assess in vivo oxidative condition of the axes, an assay employing 2',7'-dichlorofluorescein (DCFH-DA) o xidation was used. Embryonic axes from seeds stored for 8 and 42 month s showed 1.1 +/- 0.1 and 4.1 +/- 0.1 fluorescence units per min per ax es, respectively, after 24 h of imbibition. This significant increase in fluorescence was measured at all the tested incubation times. Antio xidant defences, evaluated as chemiluminescence induced by t-butyl hyd roperoxide and oc-tocopherol content, showed a significant increase wi th storage time. These data suggest that the damage due to enhanced pe roxidative events are limited by the increased amount of potent lipid soluble antioxidant.