Tropism theory
The tropism theory describes a mechanistic theory that only physical-chemical causes control the movements of plants and animals in response to external stimuli .
This principle of automatically acting causes was developed by the biologist Jacques Loeb (1859-1924), who z. B. from light stimulus experiments with animals from different animal classes concluded that the animal is "automatically led to the light source":
"The will of the animal, which in this case dictates the direction of its movement, is light, just as gravity is when stones fall or the planets move"
Only external analogies in the reaction to physical or chemical stimuli caused Loeb to postulate similar regulatory processes to stimuli in plants and animals and to negate the function of the nervous system in animals. The view taken by the doctrine of tropisms that the behavior and orientation of animals consist of tropisms as stimulus-determined, compulsory automatic reactions is not only theoretically untenable, but also experimentally refuted.
Today, tropism is understood to mean the movements of plants or their organs , which are related to the direction of the stimuli acting on them. They are to be differentiated from the nastia as structure-related movements of the plants independent of the direction of the stimulus on the one hand and from the taxia of freely moving individual organisms on the other.
literature
- ↑ quoted in W. Stempell, A. Koch, Elements der Tierpsychologie, Jena 1923, p. 597