In situ activity of α-glucosidase assayed with
α-X-gluc at pH 4.5 for 12 h, except where noted. A,
Three-day-old Arabidopsis seedling. B, Three-day-old mustard seedlings
stained at pH 4.5 (left) or 7.0 (right) for 3 h. C, Longitudinal
section through a broccoli stem. The curved surface on the right side
is a leaf abscission zone. Unstained tissue on the left is pith. Strong
staining is seen in the leaf trace indicated by the arrow. D,
Cross-section of a broccoli stem approximately 3 cm from the apex. E,
Cross-section of a broccoli stem through a leaf abscission zone. Arrows
point to strong staining in leaf traces at or above the point where
they separate from the vascular cylinder. A leaf abscission zone is on
the right side of the image. F, Same as E but approximately 4 mm basal.
Arrows point to the same leaf traces as in E, but both leaf traces are
below the point of separation from the vascular cylinder. G, Finer
detail of F. pi, Pith; ox, older xylem; yx, young xylem; ph, phloem;
ic, inner cortex; oc, outer cortex. Note the increased staining toward
the outer cortex and in the older xylem and in the leaf traces.
Bars = 1 mm (A, B, and D); 2 mm (C, E, and F); or 0.5 mm G.