Summary
The positive geotropic responses of the primary roots of Zea mays and Pisum sativum seedlings depend upon at least one growth inhibiting factor which arises in the root cap and which moves basipetally through the apex into the extending zone. The root apex (as distinct from the cap) and the regions more basal to the extending zone are not sources of growth regulators directly involved in the geotropic response. A difference in the concentration or effectiveness of the inhibitory factor(s) arising in the cap must be established between the upper and lower halves of a horizontal root. Positive geotropic curvature in a horizontal root is attributable, at least in part, to a downward lateral transport of inhibitor(s) from the upper to the lower half of the organ.
Similar content being viewed by others
References
Audus, L. J.: Geotropism. In: The physiology of plant growth and development, p. 205–242, ed. M. B. Wilkins. London: McGraw-Hill 1969.
Audus, L. J.: Linkage between detection and the mechanisms establishing differential growth factor concentrations. Proc. Symp. on Gravity and the organism. Tuxedo, New York (1967), p. 137–150, eds. S. A. Gordon and M. J. Cohen. Chicago: University of Chicago Press 1971.
Audus, L. J., Brownbridge, M. E.: Studies on the geotropism of roots. I. Growth rate distribution during response and the effects of applied auxins. J. exp. Bot. 8, 105–124 (1957).
Bennet-Clark, T. A., Younis, A. F., Esnault, R.: Geotropic behaviour of roots. J. exp. Bot. 10, 69–86 (1959).
Cerkek, L.: Effect of X-radiation on regeneration and geotropic function of barley root caps. Int. J. Radiat. Biol. 17, 187–194 (1970).
Darwin, C., Darwin, F.: The power of movement in plants. London: Appleton & Co. 1880.
Gibbons, G. S. B., Wilkins, M. B.: Growth inhibitor production by root caps in relation to geotropic responses. Nature (Lond.) 226, 558–559 (1970).
Hawker, L. E.: Experiments on the perception of gravity by roots. New Phytologist 31, 321–328 (1932).
Juniper, B. E., Groves, S., Landau-Schachar, B., Audus, L. J.: Root cap and the perception of gravity. Nature (Lond.) 209, 93–94 (1966).
Keeble, F., Nelson, M. G.: The integration of plant behaviour. V. Growth substance and traumatic curvature of the root. Proc. roy. Soc. B117, 92–119 (1935).
Keeble, F., Nelson, M. G., Snow, R.: The integration of plant behaviour. IV. Geotropism and growth substances. Proc. roy. Soc. B108, 537–545 (1931).
Konings, H.: On the indoleacetic acid converting enzyme of pea roots and its relation to geotropism, straight growth and cell wall properties. Acta. Bot. Neerl. 13, 566–622 (1964).
Konings, H.: The significance of the root cap for geotropism. Acta. Bot. Neerl. 17, 203–211 (1968).
Larsen, P.: Influence of gravity on rate of elongation and on geotropic and autotropic reactions in roots. Physiol. Plantarum (Cph.) 6, 735–774 (1953).
Pilet, P. E.: Root cap and georeaction. Nature (Lond.) 233, 115–116 (1971a).
Pilet, P. E.: Rôle de l'apex radiculaire dans la croissance, le géotropisme et le transport des auxines. Bull. Soc. Bot. suisse 81, 52–65 (1971b).
Pilet, P. E.: Root cap and root growth. Planta (Berl.) 106, 169–172 (1972).
Sachs, J. von: Über das Wachstum der Haupt- und Nebenwurzeln. Arb. bot. Inst. Würzburg 1, 385–474 (1874).
Scott, T. K., Wilkins, M. B.: Auxin transport in roots. II. Polar flux of IAA in Zea roots. Planta (Berl.) 83, 323–334 (1968).
Scott, T. K., wilkins, M. B.: Auxin transport in roots. IV. Effects of light on IAA movement and geotropic responsiveness in Zea roots. Planta (Berl.) 87, 249–258 (1969).
Shaw, S.: Hormone transport in relation to the geotropic response of roots. Ph. D. Thesis of the University of Nottingham (1972).
Snow, R.: The conduction of geotropic excitation in roots. Ann. Bot. 37, 43–53 (1923).
Snow, R.: Further experiments on the conduction of tropic excitation. Ann. Bot. 38, 163–174 (1924).
Spalding, V. M.: The trauma-tropic curvature of roots. Ann. Bot. 8, 423–451 (1894).
Syre, H.: Untersuchungen über Statolithenstärke und Wuchsstoff an vorbehandelten Wurzeln. Z. Bot. 33, 129–182 (1938).
Younis, A. F.: Experiments on the growth and geotropism of roots. J. exp. Bot. 5, 357–372 (1954).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Shaw, S., Wilkins, M.B. The source and lateral transport of growth inhibitors in geotropically stimulated roots of Zea mays and Pisum sativum . Planta 109, 11–26 (1973). https://doi.org/10.1007/BF00385449
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00385449