chemotropism Biol.
(kɛˈmɒtrəpɪz(ə)m)
[f. chemo- + Gr. τρόπος a turning + -ism.]
A condition of sensitiveness to a chemical substance in solution, exhibited by certain organisms, or parts of organisms, producing curvature towards the stimulus, termed positive chemotropism, or away from it, negative chemotropism. So chemoˈtropic a.
| 1897 Amer. Naturalist XXXI. 719 It is the difference in the concentration of the chemotropic substance in two layers..which controls movement. Positive chemotropism gradually disappears as diffusion renders the concentration slight. 1897 Nature 16 Sept. 481/2 The cause of the bending [of the hyphæ of fungi] lies in a powerful ‘chemotropic’ action. 1898 H. C. Porter tr. Strasburger's Text-bk. Bot. 263 Corresponding to the chemotactic irritability of Bacteria and spermatozoids, roots, fungus hyphæ, and pollen tubes exhibit positive and negative chemotropic curvatures. Ibid., Rheotropism..and Aerotropism, a form of chemotropism, are additional phenomena,..which stand in direct relations to certain vital requirements of plants. 1901 J. Loeb Compar. Physiol. Brain 186 The orientation of an organism by diffusing molecules is termed chemotropism. 1957 M. Abercrombie et al. Dict. Biol. (ed. 3) 49 Chemotropism. (1) (Bot.). Tropism in which stimulus has the form of a gradient of chemical concentration... (2) (Zool.). Often used synonymously with chemotaxis. 1959 Chambers's Encycl. VI. 612/1 Fertilization in many plants is controlled by chemotropic action. |
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Add: chemoˈtropically adv.
| 1895 Ann. Bot. IX. 344 The other possible explanation is that the hypha seeks the nucleus in virtue of its chemotropism, the chemotropically active substances being manufactured or accumulated in greatest quantities nearest the nucleus of the infected cell. 1979 Nature 14 June 635/1 The mature seed of Orobanche, stimulated chemotropically by diffusion of compounds from the host, germinates and its extending radicle establishes contact with the host. |