Fig. 13.

Vascular strands at the base of a maize ear around the time of pollination. Phloem strand contains carboxyfluorescein (green) and xylem strand contains safranin (red), each with 30–60 vascular elements. The large number of vascular elements presumably feed approx. 500 florets in the ear, each with a phloem terminus. The dyes were fed simultaneously to the stem 24 h earlier. Note the absence of green fluorescence in tissues surrounding the strands, indicating that the phloem axis did not release carboxyfluorescein to the apoplast. Scale bar = 1 mm. From Mäkelä et al. (2005).