Improved staining procedures for photographic documentation of phenolic deposits in semithin sections of plant tissue

Summary Several modifications of the toluidine blue O and safranin O staining procedures and a differential staining method with safranin O/azure II are described. These modifications include prestaining oxidation with sodium hypochlorite and/or poststaining treatment with iodine/potassium iodide. Greatly enhanced contrast of phenolic vacuolar inclusions is achieved by prestaining oxidation. Additionally, poststaining treatment with iodine results in a characteristic colour change of all stained tissue constituents except phenolic vacuolar inclusions. In particular, cellulose walls and cytoplasm exhibit a marked shift in colour from violet to brown (toluidine blue O) or from red to orange (safranin O). It is concluded that the methods presented can be recommended for superior photographic documentation of vacuolar polyphenol deposition in semithin sections of glycol‐methacrylate‐embedded plant tissue.