Susceptibility of Colchicum and Chlamydomonas to Colchicine

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Abstract
Resistance to colchicine occurs generally in 2 types of organisms: those which naturally contain colchicine {Colchicum and related genera) and those which have no natural contact with the alkaloid (protista and fungi). By means of temporary cultures of excised Colchicum corm roots and bacteria-free cultures of Chlamydomonas pseudococcus, resistance of these organisms to colchicine was verified. Colchicum byzantinum showed typical colchicine effects in 5% colchicine, and mitosis in Colchicum autumnale was blocked by 10% colchicine. The colchicine effects were: disappearance of the spindle, accumulation of metaphase stages, scattering of chromosomes without anaphase separation, inhibition of the cell plate, and production of 4n nuclei by the return of the blocked mitoses to interphase without anaphase separation of the chromosomes. The mitotic mechanism in Colchicum is evidently like that of other plants in that it depends upon a colchicine-sensitive process. Reproduction of Chlamydomonas is only moderately slowed by 0.015% colchicine or sat. aqueous soln. of acenaphthene. The retardation apparently decreases with increase in length of exposure, indicating acclimatization of the flagellates, or destruction of the drugs. In these 2 types of organisms, resistance to colchicine seems to reside in some extra-mitotic process.