Polar transport of auxin

The polar transport of auxin in early globular embryos is essential for the establishment of bilateral symmetry during plant embryogenesis. Interference with this transport causes a failure in the transition from axial to bilateral symmetry and results in the formation of embryos with fused cotyledons (Liu et at, 1993). 

Mitchison, G.J. (1981). The polar transport of auxin and vein patterns in plants. Philosophical Transactions of the Royal Society, London, series B, Vol. 5, pp. 461-471. 

Under this conceptual framework, hormone systems may be viewed in terms of three primary functional components (1) a site of synthesis or source of the hormone, (2) movement from the source to the site of action (this may be passive as in the diffusion of ethylene or active as in polar transport of auxin) and (3) action by the hormone upon the target site. Through such a system, hormones may initiate a new path of development at the target site or simply control an established pathway. 

Goebel K (1900) Organography of plants especially of the Archegoniatae and Spermato-phyta. Part 1. General organography. Clarendon, Oxford Goldsmith MHM (1977) The polar transport of auxin. Annu Rev Plant Physiol 28 439-478... 

Fry SC, Wangermann E (1976) Polar transport of auxin through embryos. New Phytol 77 313-317... 

Osborne DJ, Mullins MG (1969) Auxin, ethylene and kinetin in a carrier-protein model system for the polar transport of auxins in petiole segments of Phaseolus vulgaris. New Phytol 68 977-991... 

Wilkins MB, Whyte P (1968) Polar transport of auxin in Zea coleoptiles under anaerobic conditions. In Wightman F, Setterfield G (eds) Biochemistry and physiology of plant growth substances. Runge, Ottawa, pp 1051-1062 Wilkins MB, Woodcock AER (1965) Origin of the geoelectric effect in plants. Nature 208 990-992... 

Oscillatory phenomena associated v ith polar transport of synthetic auxin have also been reported in Avena and Zea coleoptiles (Newman 1963, Hertel and Flory 1968, Shen-Miller 1973 a, b), thus the oscillations of basipetal efflux of endogenous auxin found in our experiments may reflect a more general property of the mechanism involved in polar transport of auxin. 

The reported velocity of the polar transport of auxin in a variety of plant tissues has usually ranged between 10 and 15 mm h (Goldsmith 1969, 1977, Thimann 1972). Thus, the increase of amplitude after 100 minutes of lAA treatment, which we observed as far as 70 mm from the place of application, was probably not due to translocation of the applied synthetic auxin. This supposition was confirmed experimentally. In these tests " C-IAA was applied to apical ends of longer pine tissue blocks. Bioassays for hormone activity were then combined with determinations of radioactivity in receiver strips of agar gel in contact with the basal ends of short serial segments cut from the longer blocks (WoDZiCKi and Brown unpublished experiments). 

The results of experimental application of synthetic substances to stem tissue blocks showed that the oscillatory system involved in polar transport of auxin is sensitive both to growth stimulators and inhibitors, and that it reacts to them by modulation of at least the amplitude of the oscillations. Since the... 

The relation between the velocity of signal propagation and the velocity of polar transport of auxin molecules (V ), then, is as follows ... 

If there were no interaction between the auxin waves in branches and in the main stem, the branches would grow generally parallel to that stem. We propose that adjustment of the organ axes to the configuration of the auxin wave vectors in the zone of major polar transport of auxin results in deviation of the branch axes from the direction of gravity. 

As an extension of the preceding discussion about the probable consequences of interactions between auxin waves in branched shoot systems, a control mechanism capable of coordinated growth of all plant parts (axes) can be proposed. Vector fields in the zones of major polar transport of auxin in axes of various orders can be envisioned as morphogenic fields specifying positional information... 

Goldsmith MHM (1977) The polar transport of auxin. Annu Rev Plant Physiol 28 439-478... 

II. Dependence upon basipetal transport. Physiol Plant 29 288-292 Wodzicki TJ, Wodzicki AB (1980) Seasonal abscisic acid accumulation in stem cambial region of Firms silvestris and its contribution to the hypothesis of a late-wood control system in conifers. Physiol Plant 48 443 47 Wodzicki TJ, Wodzicki AB (1981) Modulation of the oscillatory system involved in polar transport of auxin by other phytohormones. Physiol Plant 53 176-180 Wodzicki TJ, Zajqczkowski S (1974) Effect of auxin on xylem tracheid differentiation in decapitated stems of Firms silvestris L. and its interaction with some vitamins and growth regulators. Acta Soc Bot Pol 43 129-148 Wodzicki TJ, Wodzicki AB, Zajqczkowski S (1979) Hormonal modulation of the oscillatory system involved in polar transport of auxin. Physiol Plant 46 97-100 Wodzicki TJ, Rakowski K, Starck Z, Porandowski J, Zajqczkowski S (1982) Apical... 

Naptalam is an unrelated benzoic acid, being a half-amide formed by the reaction of phthalic anhydride and 1-naphthylamine it has a pKa of 4 and log of 3. It is applied pre- or postemergence, and its mode of action appears to be similar to that of some of the other amides. In addition, it inhibits the cell-to-cell or polar transport of auxin. It moves in the apoplast and is expected to be symplastic to some extent though information on this is sparse. ... 

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