Figure 2

Description of the PCD gradient within a window stage lace plant leaf. The three-part differentiation of an areole within a stage 2, or window stage leaf. A) A detached stage 2, or "window" stage leaf. Note the green and pink coloration, which is due to the presence of the pigments chlorophyll and anthocyanin, respectively. B) Single side of a window stage leaf, cut at the midrib. Note the gradient of PCD, in that PCD is most advanced closest to the midrib (bottom) and least advanced towards to leaf edge (top). C) PCD has also been delineated at the level of a single areole. Within a single areole of a stage 2, or window stage leaf, cells closest to the vasculature tissue (between white and red lines) will not undergo PCD and are known as non-PCD cells (NPCD); NPCD cells often contain a marked amount of the pigment anthocyanin. The next group of cells (between red and green lines) are in very early stages of PCD and are known as early PCD cells (EPCD); EPCD cells often contain a marked amount of the pigment chlorophyll. The centermost cells (green lines inward) are cells in late stages of PCD, and are known as late PCD cells (LPCD); LPCD cells have lost most of their pigment, and are clear in nature. Scale bars (A) = 25 mm; (B) = 500 μm; (C) = 250 μm.