Fig. 4.
Boric acid excess results in secondary xylem development and lignin deposition in the outer endodermal cell walls (yellow arrows) in the CsiLAC4OE line, but not in the wild‐type (Col‐0), nor in CsiLAC17OE and miR397OE lines. (a) Primary roots from 14‐d‐old seedlings were transversely sectioned at the mature zone and stained with phloroglucinol‐HCl. Red arrows indicate the Casparian strips. Double arrowheads indicate the metaxylem. Xylem area (b) and diameter of metaxylem vessels (c) were determined by ImageJ software, and the number of metaxylem vessels was hand‐calculated. Results are mean ± SD. Asterisks indicate significant differences at: *, P < 0.05; and **, P < 0.01 by one‐way ANOVA (Student‐Newman‐Keuls method, n = 4). Bar, 50 µm.