PAS-positive reaction of phenolic inclusions in plant cell vacuoles.

The experimental data presented show that positive reaction of phenolic inclusions in the PAS test may be caused by the presence of phenolic glycosides and/or certain non-glycosidic phenols, namely flavan-3,4-diols. These both possibilities and their respective importance under conditions of conventional histological procedures are discussed. The findings emphasize the need for extreme care in interpreting the results of the PAS reaction applied to plant material.