Observational and experimental studies of the meristem of leguminous plants. II. Differentiation of the pericycle in the root tips of Pisum sativum.

The available data concerning the differentiation of the pericycle in the primary root tip of Pisum sativum, variety ‘Alaska’, may be summarized as follows.1) The root tips from 3 to 4 day old seedlings germinated in a darkroom at 24°C were fixed with Lillie's buffered neutral formalin under green light at between 2 and 4 P.M. May 17, 1976.2) By applying a combination of Lillie's formalin fixation together with methyl blue and/or Heidenhain's hematoxylin and safranin, the initial symptom of triarch xylary procambium appeared in a procambial cylinder in the transverse section of 250μ from the apical initials.3) Deeply stainable protoplasts of several layers of the pericyclic cells which were localized outside of the xylary procambium show a separation from the thin cell wall. The author would like to designate as ‘α-cells’ these stainable pericyclic cells. The α-cells were localized in the area 550μ to 2150μ from the apical initials.4) Three to six pericyclic cells in which the protoplasm scarcely stained with the dye solution should be designated as ‘β-cells’. The triarch β-cell zone was localized in a limited area, 550μ to 1750μ from the apical initials. Two or three sieve elements were observable inside of the β-cells.5) By applying a combination of the Lillie's formalin fixation and methyl blue staining, small spherical granules take a deep blue stain in the cytoplasm of the β-cell.6) The β-cell which contains these granules were interspersed within a limited area of the root tips.