THE MECHANISM OF COLCHICINE–INDUCED CYTOHISTOLOGICAL CHANGES IN CRANBERRY

Abstract

ATTEMPTS TO induce polyploidy by means of colchicine have been markedly successful with many herbaceous plants, but have been only rarely successful with woody and semiwoody plants (Dermen and Scott, 1939; Dermen, 1941; Graner, 1941; Dermen and Bain, 1944). Furthermore, results with many herbaceous plants have indicated that all new growth following colchicine treatment may show a polyploidy condition. However, the work of Satina, Blakeslee, and Avery (1940) indicates that even in such plants not all of the tissues may become polyploidized uniformly; thus the polyploid condition in treated herbaceous plants may be confined to a sector within a particular tissue or tissues, or to one whole tissue and not to others. Results with peach, a woody plant (Dermen, 1941), and cranberry, a semiwoody plant (Dermen and Bain, 1941, 1944), have indicated that in these plants the occurrence of the polyploid condition in all tissues resulting from colchicine treatment is probably very rare. When colchicine treatments of these plants did produce polyploidy, it was almost entirely confined to sectorial and periclinal cytochimeras from which, in the case of cranberry, various polyploid types have eventually been isolated and propagated. It is the purpose of this discussion to consider the cytohistological basis for sectorial and periclinal cytochimeras in colchicine-treated cranberry. A clear understanding of the facts underlying these changes will undoubtedly help to explain properly some of the complexities and to overcome some difficulties encountered in attempts to induce polyploidy in plants of semiwoody and woody types. It is hoped that the discussions presented will be of particular value in working out more successful methods of identifying and isolating polyploid material from colchicine-treated plants. The following studies are believed to have a very definite bearing on our understanding of the method by which the stem apex propagates itself, as well as of the histogenesis of primary tissues, and the ontogeny of various plant organs. It appears that induction of polyploidy by colchicine not only may result in plants of economic value, but it may also provide material for a study of many fundamental botanical problems which hitherto have been difficult of solution.