An Atypical Growth of Cabbage-Seedling Roots. I. Morphology, Histology, and Induction Conditions

Abstract

1. The induction and appearance of atypical growths on the roots of cabbage seedlings under the influence of parachlorophenoxyacetic acid (POA) are described. 2. Synthetic growth substances inducing such growth are limited to the phenoxyacetic acid series and naphthoxyacetic acid. 3. A number of sources of reduced nitrogen augment the action of the growth substance in production of these tumors. Nonspecificity of the nitrogen sources is indicated by the effectiveness of a number of amino acids and amides and of ammonium chloride. 4. Formation of the atypical growths is inhibited by buffering the medium at pH 6.0 or above; whereas buffers at pH 5.5 or below have no inhibitory effect. 5. Histological preparations of typical roots and of the atypical growths show that the tumors consist essentially of fasciated plates of lateral root tissue, with growth occurring in a massive fashion. 6. Origin of the tumors is from the pericycle, or the pericycle and endodermis combined, of the primary root. Xylem, cortex, and cpidermis are inactive in producing the growths and do not seem to be affected by POA.