Histochemical Determination of Polysaccharides in Fruit Pulp Cell Walls

Abstract

For histochemical investigations of fruit pulp, before fixation tissue should be dehydrated in absolute alcohol at dry ice temperature (-78°C) to avoid cell shrinkage. Cell wall polysaccharides can be removed selectively without section losses provided the sections are mounted on slides coated with a solution made with 0.5g gelatin, 0.2g chrome alum and 100ml H₂O. Pectic acids are removed by overnight pectinase treatment at 30°C, followed by 2 hrs in 0.5% aqueous ammonium oxalate at 90°C. Hemicellulose and noncellulosic polysaccharides are removed by 12 hr treatments respectively with 4% and 17.5% aqueous NaOH at room temperature, with slices kept affixed by a coating made up by dipping the slides into a 0.5% ethyl cellulose solution in a 4:1 mixture of toluene and absolute ethanol.
After the extraction the coating is dissolved away and periodic acid Schiff staining is subsequently used to detect and evaluate remaining cell wall polysaccharides.