The Different Components of the Movement and the Areas of Retention of Labelled Molecules after Application of [3H]‐ indolyl‐acetic acid to the Apical Bud of Vicia faba

Abstract

After application of [3H]‐auxin (0.8 nmol) to a young leaf of Vicia faba L. cv. Aguadulce. about 6% (1.1 × 10‐2 nmol) of applied IAA enters the stem during the first 6 h of transport. This corresponds to a [3H]‐auxin flux which is probably not very different from the endogenous flux. A wave of [3H]‐ auxin moves down to the roots mainly among preferential pathways situated in the vascular bundle. This movement is accompanied and followed by certain events: (I) In the upper part of the stem, some radioactive molecules leave the pathways of polar transport and enter the young leaves near the donor leaf. (2) In other parts of the stem, the auxin transport is highly polar. As the peak of the wave approaches and passes a node with an axillary bud. and for a few hours afterwards, there is no clearly detectable radioactivity in this bud, although the nodal tissues are very radioactive. (3) A retention of labelled molecules often occurs in the nodes. (4) Retention of label is regularly seen in the basal part of the first internode and in the hypocotyl, which together form that part of the axis where Ifle highly inhibited cotyledonary buds are found. This retention is still manifest a week after the downward transport of [3H]‐auxin. (5) After 48 h. a high proportion (about 45%) of the [3H]‐auxin exported by the donor leaf is found in the roots. (6) Subsequently, a part of the label returns to the upper parts of the plant, and especially to the leaves, where it normally appears to be immobilized. (7) As time goes on some labelled molecules, probably coming from different areas, enter the axillary buds.

Auxin and cytokinin related gene expression during active shoot growth and latent bud paradormancy in Vitis riparia grapevine

“…Several studies in trees have also shown that removal of the apical buds enhanced outgrowth of the buds immediately below them, but the same was not apparent for more distal basal buds (Fosket, 1968;Rohde et al, 1997;Suzuki et al, 1990). Auxin applications resulted in a similar outgrowth pattern in Scrophularia arguta, Vicia faba (broad bean) and Ipomoea nil (Japanese Morning Glory) (Bourbouloux and Bonnemain, 1979;Chern et al, 1993;Prasad et al, 1993). Similarly, cytokinin applied to buds at nodes three or four (from tip) of pea plants with four fully expanded leaves did not promote the outgrowth of these buds, but could promote outgrowth of buds at node two (King and Van Staden, 1988).…”

Regulation of vascular differentiation in leaf primordia during the rhythmic growth of Gnetum africanum

“…These results, like ours, suggest that one or several stimuli from young leaves control the differentiation of the vascular tissues. Auxin synthesized in young leaves (Humphries and Wheeler 1964) accumulates particularly in the region of the bundles during their course of differentiation (Bourbouloux et al 1973;Bourbouloux and Bonnemain 1974;Miginiac et al 1978) and therefore appears to be one such stimulus. Defoliation considerably reduced vascular differentiation in the stem and the replacement of the young leaves by the external application of auxin restored their action on vascular differentiation (Wangerman 1967).…”

“…Auxin causes an increase in the level of abscisic acid while a high level of the latter reduces the tissue level of auxin (Lovell 1977). Taking into account the role of auxin in vascular differentiation, a very low level of this growth regulator could very well be the cause of nondifferentiation into vascular bundles, and because of their role in the transport of nutritive molecules and hormones (Bourbouloux and Bonnemain 1979;Miginiac 1974;Miginiac et al 1978;Wardlaw 1965), the absence of these bundles could also explain the inhibition of leaf primordia.…”

Effet du refroidissement local de la tige sur le transport du AIA exogène en provenance du bourgeon apical et sur la croissance des bourgeons axillaires

“…Nous avons verifie que Fensemble du systeme et notamment l'application de vaseline n'a pas d'effet sur ie transport de l'auxine a 22°C. Application de l'auxine radioactive et methode d'analyse Une heure apres la mise en place de la barriere thermique, le AIA-^H (activite specifique 925 GBq mmor\ CEA, France) ou le AlA-2-"C (activite specifique 925 MBq mmol"', CEA, France) sont appliques sur une jeune feuille du sommet de la piante, seion une methode deja decrite (Bourbouloux et Bonnemain 1974 : emplacement de la barriere thermique a 5'C Tableau 1. Quantite moyenne de radioactivite (dpm) retrouvee par piante au-dela de ia barriere thermique (2 cm de large) 15 h apres l'application du AIA-^H sur une jeune feuiSie du bourgeon terminal (n = 10 plantes).…”

“…Quantite moyenne de radioactivite (dpm) retrouvee par piante au-dela de ia barriere thermique (2 cm de large) 15 h apres l'application du AIA-^H sur une jeune feuiSie du bourgeon terminal (n = 10 plantes). la technique precedemment decrite (Bourbouloux et Bonnemain 1979).…”