Cytochemistry of pit plugs in Bossiella californica (Corallinales, Rhodophyta)

Abstract

The chemical composition of pit plugs in the articulated coralline red alga Bassiella californica (Decaisne) Silva (Rhodophyta) was investigated using light and electron microscopic staining methods, enzyme digestion, and FITC-labelled lectin probes. Light microscopic cytochemical techniques indicated that the outer cap layer was composed of glycoproteins. It gave a reaction with the periodic acid-Schiff procedure, specific for carbohydrates, and with mercuric bromophenol blue, a protein stain. The pit plug core was reactive only with the protein stain. Twenty-two enzymes were tested for their effects on the ultrastructure of pit plugs, but only three proteolytic enzymes, namely proteinase K, pancreatin and pronase E, caused any discernible change. All three enzymes digested the outer plug cap layer, first removing reactivity to phosphotungstic acid-chromic acid, a selective ultrastructural stain, and then removing the cap layer from the section. The plug core and inner cap layer were not affected. The ten lectins tested showed no binding to any region of the pit plugs.