Summary
Transport of indolyl-3-acetic acid (IAA) was studied during the phototropic responses of intact shoots and detached coleoptiles of Zea mays L. and Avena sativa L. The use of a high specific activity [5-3H]IAA and glass micropipettes enabled asymmetric application of the IAA to be made to individual coleoptiles with minimal tissue damage.
A unilateral stimulus of 2.59×10-11 einstein cm-2 of blue light, probably in the dose range of the first positive phototropic response, caused significant net lateral movement of radioactivity from [5-3H]IAA away from the illuminated side of intact shoots and detached coleoptile apices of both Avena and Zea. The magnitude of the net lateral movement was 15.3% in Zea seedlings and 12.3% in Avena seedlings. Chromatographic analyses indicated that the movement of radioactivity reflected that of IAA. A phototropic stimulus of 1.24×10-7 einstein cm-2, which was probably in the second positive dose range, caused significant lateral movement of radioactivity in intact shoots and detached coleoptiles of Zea but not of Avena.
In intact Zea seedlings, neither phototropic dosage affected the longitudinal transport of IAA. In intact Avena seedlings, first positive stimulation inhibited longitudinal transport only when the IAA was applied to the illuminated side of the coleoptile, but second positive stimulation inhibited basipetal movement of IAA regardless of the side of application.
Exposing the intact seedlings to red light before phototropic stimulation abolished lateral transport after a first positive stimulus in Zea and in Avena.
Phototropic stimulation can thus induce a lateral transport of IAA towards the shaded side of the coleoptiles of both Zea and Avena seedlings, and can affect longitudinal movement of IAA in the coleoptile of Avena. However, since phototropic curvature was observed under certain conditions in the absence of either of these effects, the extent to which they are involved in the induction of asymmetric growth in a stimulated coleoptile has yet to be resolved.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Boysen Jensen, P.: Die phototropische Induktion in der Spitze der Avenacoleoptile. Planta (Berl.) 5, 464–477 (1928)
Briggs, W. R.: Mediation of phototropic responses of corn coleoptiles by lateral transport of auxin. Plant Physiol. 38, 237–247 (1963a)
Briggs, W. R.: Red light, auxin relationships, and the phototropic responses of corn and oat colcoptiles. Amer. J. Bot. 50, 196–207 (1963b)
Briggs, W. R.: The phototropic responses of higher plants. Ann. Rev. Plant. Physiol. 14, 311–352 (1963c)
Briggs, W. R., Tocher, R. D., Wilson, J. F.: Phototropic auxin redistribution in corn coleoptiles. Science 126, 210–212 (1957)
Cane, A. R., Wilkins, M. B.: Independence of lateral and differential longitudinal movement of indoleacetic acid in geotropically stimulated coleoptiles of Zea mays. Plant Physiol. 44, 1481–1487 (1969)
Chon, H. P., Briggs, W. R.: Effect of red light on the phototropic sensitivity of corn coleoptiles. Plant Physiol. 41, 1715–1724 (1966)
dela Fuente, R. K., Leopold, A. C.: Lateral movement of auxin in phototropism. Plant Physiol. 43, 1031–1036 (1968)
Gordon, S. A., Shen-Miller, J.: Auxin relations in phototropism of the coleoptile: a reexamination. In: Biochemistry and physiology of plant growth substances, p. 1097–1108, Wightman, F., Setterfield, G., eds. Ottawa: The Runge Press Ltd. 1968
Naqvi, S. M., Gordon, S. A.: Auxin transport in Zea mays coleoptiles. II. Influence of light on the transport of indoleacetic acid-2-14C. Plant Physiol. 42, 138–143 (1967)
Pickard, B. G., Thimann, K. V.: Transport and distribution of auxin during tropistic response. II. The lateral migration of auxin in phototropism of coleoptiles. Plant Physiol. 39, 341–350 (1964)
Shaw, S., Gardner, G., Wilkins, M. B.: The lateral transport of IAA in intact coleoptiles of Avena sativa L. and Zea mays L. during geotropic stimulation. Planta (Berl.) 115, 97–111 (1973)
Shaw, S., Wilkins, M. B.: Auxin transport in roots. X. Relative movement of radioactivity from IAA in the stele and cortex of Zea root segments. J. Exp. Bot. 25, 190–207 (1974)
Shen-Miller, J., Cooper, P., Gordon, S. A.: Phototropism and photoinhibition of basipolar transport of auxin in oat coleoptiles. Plant Physiol. 44, 491–496 (1969)
Shen-Miller, J., Gordon, S. A.: Hormonal relations in the phototropic response. III. The movement of C14-labelled and endogenous indoleacetic acid in phototropically stimulated Zea coleoptiles. Plant Physiol. 41, 59–65 (1966)
Thornton, R. M., Thimann, K. V.: Transient effects of light on auxin transport in the Avena coleoptile. Plant Physiol. 42, 247–257 (1967)
Wilkins, M. B.: Hormone movement in geotropism. In: Gravity and the organism, p. 107–124, Gordon, S. A., Cohen, M. J., eds. Chicago: University of Chicago Press 1971
Zimmerman, B. K., Briggs, W. R.: Phototropic dosage-response curves for oat coleoptiles. Plant Physiol. 38, 248–253 (1963)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Gardner, G., Shaw, S. & Wilkins, M.B. IAA transport during the phototropic responses of intact Zea and Avena coleoptiles. Planta 121, 237–251 (1974). https://doi.org/10.1007/BF00389324
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00389324