An Atypical Growth of Cabbage Seedling Roots. Iii. Tissue Culture and Physiological Comparisons of Typical and Atypical Roots

Induction of an atypical growth of cabbage roots under sterile conditions (8) by p-chlorophenoxyacetic acid (POA) has led to a comparative study of typical and atypical growth. The atypical growth (tumor) is a massive tissue, as opposed to the thin, straight morphology of a normal root. The The words tumor or callus as applied to cabbage root growths are intended only as a convenient abbreviation of atypical growth. The material is not malignant, and therefore cannot be considered a true tumor. It differs greatly in degree of organization from the usual plant calluses. It is not as disorganized as the usual callus or tumor tissue culture, but is seen to consist of many abnormal lateral roots growing in a nondivergent, fasciated condition. Since this tissue can be grown under conditions identical with those of the normal roots from which it is derived, it becomes possible to compare the physiological and biochemical characteristics of the two. Aside from the descriptive interest of such a study, the information gathered might be pertinent to the mechanism of induction of the atypical growth, or to the causal relationships between the new biochemical activities and the new morphology. The purpose of the present work has been to compare tumorous roots of POA-treated plants with typical roots of untreated plants in regard to growth in tissue culture, dry weight, total nitrogen and protein content, and some respiratory characteristics ; and to compare the distribution of nitrogen and dry weight in entire treated and untreated seedlings.