Date of Award
The fact that shoots grow upwards and roots grow downwards is common knowledge. These recognized tendencies are called "geotropic reactions". We apply the term, "positive geotropism" to the tendency of roots growing downwards; meaning that they respond in a positive manner to the pull of gravity. To the response of shoots we apply the term, "negative geotropism", which signifies that their growth is away from the pull of gravity.
The response of plants to external forces such as gravity has long been a subject of research. Many theories have been advanced attempting to explain the basic principles involved in the geotropic response, yet the mechanism of this phenomenon remains unknown. It is the purpose of this paper to review some of the theories that have been advanced to explain the geotropic response and to present some preliminary results of experiments on the geotropic response of roots.
Quarles, Nancy Redd, "AN HISTORICAL AND EXPERIMENTAL ACCOUNT OF GEOTROPISM" (1957). Theses, Dissertations & Honors Papers. 464.