Structural changes in the carrot petioles from stage 1 (A), stage 2 (B), stage 3 (C), stage 4 (D), and stage 5 (E).

<p>Collenchyma (C), epidermis (Ep), exodermis (Ex), phloem (P), and xylem (X) are marked in the Figure. Scale bars in A, B, C, D, and E are 100 μm in length.</p>