As we saw in previous lectures, plants are "rooted" to one spot. As a consequence they can not avoid adverse conditions such as drought, heat, cold etc. yet are able to survive seemingly extreme conditions. Almost all aspects of plant development and physiology are influenced and directed by plant hormones. In today's lecture we look at the discovery of plant hormones in general - watch out for the appearance of an unlikely scientist - and look at specific effects of the phytohormone auxin, such as phototropism in shoots and geotropism in the roots, and apical dominance. Copyright 2012 La Trobe University, all rights reserved. Contact for permissions.