Thigmonastic Coiling of Tendrils of Passiflora quadrangularis is Not Caused by Lateral Redistribution of Auxin

The effect of thigmotropic stimuli on the distribution of exogenously applied indoleacetic acid in intact tendrils of Passiflora quadrangularis L. has been investigated. Tips of tendrils were dipped in solutions of IAA‐2‐14C for 12 h and subsequently stimulated by exposure to carbon dioxide or mechanically by rubbing. The content of 14C in dorsal and ventral halves was analysed before, during and after coiling. Our experiments failed to detect any difference from the initial dorsal: ventral ratio of 14C (44:56) as a possible consequence of stimulus or of coiling. This suggests that thigmotropic curvature is not dependent on lateral movement of auxin, supporting a theory of a built‐in asymmetrical reaction of the tissues to equal amounts of auxin and CO2, respectively.