Simple method for differential staining of paraffin embedded plant material using toluidine blue O

Differential staining of paraffin embedded plant material is accomplished without removing the paraffin. Material fixed in 3% glutaraldehyde in 0.02 M phosphate buffer is dehydrated, embedded, sectioned, and mounted on glass slides using conventional methods. The slides are placed in 0.05% toluidine blue O in distilled water for 2-30 min, rinsed in water for 1 min, and allowed to air dry. Paraffin is removed with 2 changes of xylene and the cover slip mounted with resin. Lignified tissue, suberized tissue, and some tannins are stained blue-green, while nonlignified walls are stained red-purple. An advantage of the method is the short time required for staining and mounting. Also, critical counterstaining is not required.