Rhizoid differentiation in Spirogyra I. Basic features of rhizoid formation

Several types of rhizoids occurring in the process of differentiationin Spirogyra sp. are described and their interrelation was elucidated.There are two differentiation sequences: P_pPRh_ros or PpPRh_rodRh_ros(for explanation of abbreviations see p. 533), although undersome conditions the sequences ceased halfway through. The initiationtime for rhizoid formation had no relation to the cell cyclestage. The difference in growth patterns between the rhizoidand ordinary filament cells was demonstrated with Calcofluor-stainingand centrifugation. The optimum temperature and pH of the culture medium for rhizoiddifferentiation were 20?C and pH 7, respectively. A contactstimulus was not necessary for induction. Of the several environmental factors examined, light was themost important, for rhizoid formation, since a rhizoid was inducedonly when light was given after cutting the filament. (Received December 14, 1972; )