(A) In ambient light. (B) in the dark.The robust light emission belongs to the cells of shoot pith parenchyma (in the center of the stem). Weaker bioluminescence is observed from core parenchyma cells (periphery of the stem). Maximal light intensity corresponds to the region of the axillary bud — newly forming meristem — and surrounding parenchymatous cells. Completely lignified tissues, xylem and phloem, with cambium in between, lack luminescence (visible at the right side of the stem as a dark band). The images are representative of two experiments with similar results.