Fig. 5. Whole mounts of excised quiescent centers (QC) from roots that have had their root cap (RC) excised, and subsequent regeneration allowed to proceed for various periods of time. During the last 2-3 hours of regeneration roots are treated with the redox sensitive dye carboxy H2DCFDA. (A,B) Control, time zero; RC excised just prior to placing roots in dye. Photographed in white light (A) or white plus UV (B). (C,D) 24 hours after removal of the RC. Photographed in white light (C) or UV (D). Note the disappearance of fluorescence from the QC, indicating a less oxidizing environment. (E,F) 48 hours after removal of the RC. Photographed in white light (E) or UV (F). A low level of fluorescence is detected in the center of the tissue. (G,H) 72 hours after removal of the RC. Photographed in white light (G) or UV light (H). The fluorescence has expanded to include an area similar to that of the control (Fig. 7B). Scale bar, 100 µm.