Root formation in vine (Vitis vinifera L. cv. Albariño) was accompanied by at first a rise and then a fall in total peroxidase (EC 1.11.1.7) activity in the explant. These variations ran parallel to similar changes in the amount of the three cathodic isope‐roxidases detected, the most abundant of which, C2, also exhibited IAA oxidase activity. The anodic isoperoxidase bands detected were very weak and underwent no variation during rooting. Changes in the opposite direction (a fall followed by a rise) were shown by certain endogenous phenolics, including monoferuloyl, monocaffeoyl and mono‐ρ‐coumaroyl tartaric acids, some of which may act as auxin protectors.
Auxin protectors and IAA oxidase activity were comparatively analyzed in the upper and the lower parts of shoots of chestnut (Castanea sativa Mill.) cultivated in vitro with indolebutyric acid (IBA) pretreatment. Rhizogenesis of the shoots is accompanied by an increase in auxin protectors in the lower parts and by a decrease of these protectors in the upper parts. Besides, the IAA oxidase activity declines in the basal parts during the rooting process while it increases in the upper ones. These biochemical events would enhance the IAA level in the rooting region of the shoots. In untreated, non‐rooted cuttings, the IAA oxidase activity remains low in the upper parts and high in the basal parts of the shoots. The results thus indicate that the IBA treatment may control the endogenous auxin level of the cuttings, either through a direct regulation of the IAA oxidase system or more indirectly through the transport of auxin protectors.
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