Cell-specific expression of MIP-A, MIP-B, and MIP-F in stem sections. Fixed cross-sections (8–10 μm) of stems were used and treated as described in Figure 2. A, C, and E represent images after staining with preimmune serum for MIP-A, MIP-B, and MIP-F, respectively. B, D, and F are stained with serum against MIP-A, MIP-B, and MIP-F, respectively. Bars in A and B represent 70 μm, and in C through F, 150 μm. Arrows in B point to phloem elements, arrows in D to old xylem vessels and xylem parenchyma, and arrows in F to developing xylem vessels.