Staining Paraffin-Embedded Plant Tissues with Acridine Orange

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Abstract
Stem, leaf, and bud tissue of sweet potato, tomato, and pepper were embedded in paraffin, sectioned, mounted, and stained with 0.01, 0.1 and 1% aqueous and 0.1% alcoholic solutions of acridine orange. Temporary and durable mounts were prepared and irradiated under short and long wave ultraviolet light. Intensity and specificity of the fluorescence imparted to tissues were chiefly affected by type of fixative. Best results were obtained with fixatives containing formalin but not acetic acid. Tests on the effect of pH obtained with McDvaine''s buffer between 4.5 and 8.3, and made only with the aqueous stain, showed 6-8 to be optimal. Aqueous staining 1 hr. in 0.1% solution, pH 6-8 is recommended for temporary mounts. Durable mounts in a nonfluorescent resin can be made after differentiation in buffer and dehydration in dioxan solutions.