A Comparison of Auxin Destruction by Tissue Extracts and Intact Tissues of the Fern, Osmunda cinnamomea L.

Abstract

In the fern O. cinnamomea, auxin diffusion data show that the only disappearance of endogenous auxin in the leaf rachis is in the zone of active elongation. The final rate of diffusion of indoleacetic acid, applied in a lanolin-water emulsion to the epidermis of the rachis below the zone of active elongation is constant for sections of rachis of comparable age and diameter, and independent of the length of the transport path. It is therefore suggested that there is no endogenous destruction within this tissue. A comparison of in vivo auxin disappearance and in vitro auxin inactivation by different parts of the rachis shows that extracts of tissues above and below the zone of elongation will destroy auxin, although none disappears within these tissues while they are still intact. Ether extractions of various parts of the rachis indicate that there is also no disappearance of ether-extractable auxin from tissues below the zone of elongation, although considerable auxin is moving through these tissues. Water extracts of rhizome tissue entirely fail to destroy added indoleacetic acid, although ether extractions clearly show a disappearance of endogenous auxin in the rhizome upon removal of auxin producing leaves. Therefore, the auxin-inactivating enzyme system found in the extracts is considered to be of little importance in the normal growth physiology of this fern as a factor limiting leaf growth.