Plasma membrane intactness, demonstrated by Evans Blue staining. (A) Window stage leaf stained with Evans Blue. Note the gradient of PCD that exists, with the outermost cells being non-PCD (NPCD) stage cells and the centermost being late-PCD (LPCD) stage cells and the centermost being late-PCD stage cells (LPCD). Also note that only LPCD stage cells, with collapsed PMs, stain blue. (B) Higher magnification of a similar leaf as shown in panel A, again note that only cells with collapsed PMs possess blue staining. Scale Bars: A = 100 μm, B = 50 μm.