The older inner xylem in a woody stem that no longer conducts water and minerals is known as which term?

The older inner xylem in a woody stem that no longer conducts water and minerals is known as which term?

• A. Sapwood
• B. Heartwood
• C. Cambium
• D. Phloem

Answer: (B)

In woody stems, xylem develops into two zones as it ages: the outer, living sapwood that continues to conduct water and minerals, and the inner, older xylem that loses its function for transport. The inner xylem becomes heartwood as it ages, dying and accumulating substances like tannins and resins. This non-conductive wood provides structural support for the plant, which is why it’s preserved inside the stem even though it no longer moves water. The other tissues mentioned aren’t the non-conductive inner xylem: sapwood conducts water, cambium is the growing layer that produces xylem and phloem, and phloem transports sugars outside the xylem. So the term for the older inner xylem that no longer conducts is heartwood.

In woody stems, xylem develops into two zones as it ages: the outer, living sapwood that continues to conduct water and minerals, and the inner, older xylem that loses its function for transport. The inner xylem becomes heartwood as it ages, dying and accumulating substances like tannins and resins. This non-conductive wood provides structural support for the plant, which is why it’s preserved inside the stem even though it no longer moves water. The other tissues mentioned aren’t the non-conductive inner xylem: sapwood conducts water, cambium is the growing layer that produces xylem and phloem, and phloem transports sugars outside the xylem. So the term for the older inner xylem that no longer conducts is heartwood.