Fig. 3. Whole mounts of excised quiescent centers (QC) with or without the adjacent proximal meristem (PM); from roots pre-treated for 2-3 hours with the redox sensitive dye carboxy H2DCFDA. Fluorescence indicates a relatively oxidizing environment. (A,B) An isolated QC with its distal face showing. Photographed in white light (A) or in UV light (B). (C,D) QC and adjacent PM. Photographed simultaneously with white and UV light (C), or in UV light only (D). Note the metaxylem initial (xi arrow) on the distal face of the PM. Scale bar: 100 µm.