The Role of Tannins in Neutral Red Staining of Pine Leaf Vacuoles

Abstract

The vital stain, neutral red, was retained by the cell vacuoles of white pine, Pinus strobus L., through the fixing and embedding process. The results obtained were equivalent to living tissue when the material was fixed in 10% formalin or Bouin''s solution and embedded in wax. Chromatographic studies indicated that water-soluble tannins were responsible for adsorption of the neutral red, but only after treatment with formaldehyde. Analyses with other mono-, di-, and trihydroxy phenols suggested that ferric ions and phenols with at least 3 hydroxyl groups per molecule were essential to the reaction.