EFFECT OF TRANSVERSE GRAVITY STIMULATION GIBBERELLIN AND INDOLEACETIC ACID UPON POLAR TRANSPORT OF IAAC14 IN STEM OF HELIANTHUS ANNUUS

Using IAAC14, polar transport has been studied in Helianthus annuus shoots in which stem elongation was inhibited by a transverse gravity stimulus induced by horizontal orientation of the plant with daily rotation. Marked inhibition of polar transport of IAA C14 occurred in the treated plants. A similar degree of inhibition occurred in the upper and lower halves of non‐rotated horizontally trained shoots. Horizontal orientation of stem segments during the transport test had no consistent effect upon IAA transport. Pretreatment of erect plants with gibberellin greatly enhanced IAAC14 transport and also reduced the inhibitory effect of horizontal orientation. Pretreatment of erect plants with non‐radioactive IAA or ethylene inhibited transport of IAA C14 and induced the same symptoms in the shoot as the transverse gravity stimulus. The similarities between the response of the auxin transport system to gravity stimulation, IAA and ethylene are discussed. Copyright © 1969, Wiley Blackwell. All rights reserved