From Big Medical Encyclopedia

TROPYZMY (Greek tropos turn, the direction) — the movements of the growing bodies or change of orientation of separate parts of a motionless in general plant caused by influence of an external irritant (light, gravity, etc.). Nek-ry researchers identify T. with a taxis (see).

Depending on the nature of an irritant (light, electricity, warmly, any chemical substances, etc.) tropisms (also, as well as a taxis) subdivide into a photo (gelio) - chemo, galvano-and thermotracks-isms. Mark out also specific activity of plants in response to action of force of terrestrial gravitation (geotropism), a touch (a stereo - and a thigmotropism), pressure (baro-trogshzm); in physiology pepolzuyet-sya the term «neurotropism», the Crimea designate the phenomenon of the directed growth of nerve fibril at action various physical. - chemical factors. T. have adaptive value, providing to an organism a possibility of the choice of rather comfortable conditions in relation to a certain environmental factor.

Bibliogrb l I x e r L. Ya. Kurs of the general biology, page 82, M. — L., 1935; Fundamentals of the general biology, under the editorship of E. Libbert, the lane with whom., page 273, M., 1982.

V. N. Yarygin.