OXIDATIVE STRESS AFFECTS ALPHA-TOCOPHEROL CONTENT IN SOYBEAN EMBRYONIC AXES UPON IMBIBITION AND FOLLOWING GERMINATION

The content of alpha-tocopherol (alpha T) in isolated soybean (Glycine max, var Hood) embryonic axes was measured upon germination. Dry, hig h-vigor axes contained 1.2 +/- 0.1, nmol/axis and after an increase du ring the initial 6 h of imbibition, there was a decline to 1.0 +/- 0.1 nmol/axis at 24 h of incubation. Incubation in the presence of the re dox-cycling agent paraquat (4 mM) for 24 h increased the alpha T conte nt to 1.9 +/- 0.2 nmol/axis. When the incubation medium was supplement ed with 500 mu M Fe-EDTA over 24 h, the content of alpha T increased t o 1.8 +/- 0.1 nmol/axis. Isolated axes from soybean seeds stored for 5 6 months contained 6.5 +/- 0.3 nmol of alpha T/axis after 24 h of imbi bition as compared to 1.0 +/- 0.1 nmol of alpha T/axis in axes from so ybean seeds stored for 8 months. In all of these experimental situatio ns, oxidant production as assessed in vivo by a fluorometric assay was increased by 4 mM paraquat (8-fold), 500 mu M iron (2-fold), and 56 m onths of storage (4-fold) after 24 h of imbibition. The data presented here suggest that the cellular content of alpha T is physiologically adjusted as a response to conditions of oxidative stress.