Transmission electron micrographs of 5, 8, and 12 DAP endosperm cell walls labeled with the LM11 (left-hand column) antibody for arabino-(1→4)-β-d-xylan and those pretreated with α-l-arabinofuranosidase before labeling with LM11 (right-hand column). A, Immunogold-labeled section of cellularizing endosperm at 5 DAP showing no gold particles in the cell walls. B, Treatment with α-l-arabinofuranosidase prior to LM11 labeling reveals arabino-(1→4)-β-d-xylan to be present in the early endosperm cell walls. C, No labeling using the LM11 antibody can be seen in the cell walls of the starchy endosperm at 8 DAP. D, LM11 labeling after pretreating 8 DAP sections with α-l-arabinofuranosidase reveals significant gold labeling along starchy endosperm cell walls. E, Gold particles are absent when the peripheral starchy endosperm at 12 DAP has been labeled with the LM11 antibody. F, The presence of arabino-(1→4)-β-d-xylan is revealed in the peripheral starchy endosperm of 12 DAP sections when treated with α-l-arabinofuranosidase prior to LM11 labeling. Bars = 0.2 μm. cw, Central starchy endosperm wall; pcw, peripheral starchy endosperm wall.