Which statement about the cambium’s role in diameter growth is accurate?

• A. It stores water
• B. It forms bark
• C. It produces new xylem inward and phloem outward, enabling secondary growth
• D. It conducts photosynthesis

Answer: (C)

Diameter growth is driven by the vascular cambium, a lateral meristem that adds new cells to both sides of the stem. Each time it divides, it produces secondary xylem on the inside (toward the center) and secondary phloem on the outside (toward the bark). This outward-inward production creates more wood and more inner bark, increasing the stem’s girth and forming the basis for secondary growth. Over time, the pattern of cambial activity gives rise to annual growth rings in temperate species.

Water storage is handled by parenchyma and related tissues, not the cambium, so that’s not its role. Bark formation involves the cork cambium contributing to outer bark, not the vascular cambium. Photosynthesis occurs in chloroplast-containing cells in leaves (and some green stems), not in the cambium.