Differential effects of ethylene on pith peroxidase of intact tobacco plants and excised tissue.

Ethylene increases the pith peroxidase activity of intact tobacco plants (Nicotiana tabacum) but not of excised pith, either at atmospheric or reduced pressures. In the intact plant, the increased activity involves augmentation of the two constitutive anodic isoperoxidases. In the excised pith, ethylene strongly represses one injury-induced isoperoxidase, while not markedly affecting other isozymes known to be repressed by auxin. Thus, the previously described auxin-induced repression of peroxidase is not due mainly to auxin-induced ethylene formation.