The region of a plant stem in which cells divide to increase its diameter is

Step 1: Analyze the question The question asks which region of a plant stem contains cells that divide to make the stem wider (increase in diameter). This is called secondary growth or growth in girth.

Step 2: Explain the concept Plants grow in two main ways:

• Primary growth (growth in length) happens at the apical meristems at the tips of shoots and roots.
• Secondary growth (growth in thickness) happens at the lateral meristems. In stems, the lateral meristem is the vascular cambium, which lies between the xylem and phloem in dicot stems.

The cambium divides actively. It produces new xylem (secondary xylem) on the inside and new phloem (secondary phloem) on the outside. This thickens the stem year after year, which is why trees grow wider and form annual rings.

Step 3: Check each option

• A. Cambium: A meristematic tissue whose cells keep dividing. It increases stem diameter. ✔
• B. Phloem: Conducts manufactured food (sucrose) from the leaves to other parts. Its cells do not divide to thicken the stem.
• C. Xylem: Conducts water and minerals and gives support. It is produced by the cambium but does not divide itself.
• D. Collenchyma: A living supporting tissue with cell walls thickened at the corners. It gives flexible support to young stems and does not divide to increase diameter.

Step 4: Answer The cambium is the region of cell division that increases the diameter of a plant stem.

Exam tip: Link "C" in cambium with "Circumference/girth". Remember that apical = length, lateral (cambium) = width. If a question mentions "division," "meristem," or "increase in thickness," think cambium.