Growth Induction in Cultures of Haplopappus Gracilis. I. The Behavior of the Cultured Cells

Blakely, L. M., and F. C. Steward. (Cornell U., Ithaca, New York.) Growth induction in cultures of Haplopappus gracilis. I. The behavior of the cultured cells. Amer. Jour. Bot. 48(5): 351–358. Illus. 1961.—Because of the unusual cytology of Haplopappus gracilis (2n = 4), a study has been made of the growth of its stem tissue in culture. Although growth may occur on a basal medium supplemented in various ways, it was stimulated for present purposes by the use of a basal medium containing casein hydrolysate, coconut milk (2–10% by volume) and naphthaleneacetic acid (0.5 p.p.m.). A definite synergism between coconut milk and naphthaleneacetic acid was demonstrated. The general form of the colonies so obtained responds to the composition of the medium, and certain effects of pigmentation indicate that the biochemistry of the cultured tissue is also a function of the conditions. The Haplopappus cultures were maintained in liquid culture either in the form of free cells or of the small cell clusters to which they readily gave rise. The form of typical cells and cell clusters is described, and stress is laid upon the range of growth forms that are encountered. Variations in suspensions of cells, or small cell clusters, may be investigated by the application of simple microbiological techniques. Haplopappus gracilis is thus a useful material for the further study of growth and morphogenesis by tissue culture techniques.