The size and distribution of individual cell organelles (plastids, mitochondria, oleosomes, protein bodies) and of the three main storage compounds (starch, fat, protein) have been studied micromorphometrically at the electron microscopical level in ray cells of poplar wood during early winter. The three cell types of the rays (contact cells, isolation cells, cells of the contact cell rows) show remarkable differences in size and distribution of organelles and of storage material which manifest an existing physiological specialisation of these cells. The micromorphometric data on storage compounds are compared with the biochemically determined amounts of starch, proteins, fat-bound glycerol, and of various sugars in the wood. At the stage investigated, a prominent protein storage, an extensive starch-sugar transition, but no indications for a starch-fat transition are found. Micromorphometry proved to be a useful tool for the detection of cell-specific differences within a tissue.
