Question

Which of the following is not included in a bark?

• A. Secondary xylem
• B. Secondary phloem
• C. Periderm
• D. Both (A) and (B)

Answer 1

The correct option is A

Secondary xylem

The correct option is A.

Explanation of correct option:

1. The outermost layers of roots and stems of woody plants are known as the bark.
2. Barks are found in woody vines, trees, and shrubs.
3. It overlays the wood and comprises the outer bark and the inner bark.
4. A complex tissue, which comprises not only conducting cells and non-living supporting cells but also living components are known as secondary xylem.
5. Secondary xylem also known as wood is produced by the vascular cambium layer of cells.
6. Bark comprises all the tissues external to the vascular cambium, therefore, secondary xylem is not present in the bark.

Explanation of incorrect options:

Option B:

1. The inner soft bark comprises secondary phloem tissue, whose innermost layer conducts food from the leaves to the remaining parts of the plant.

Option C:

1. The bark of a tree comprises a secondary covering known as the periderm.
2. It forms on several non-woody plants and small woody stems.
3. In bark, the periderm substitutes the epidermis, and functions as a protective covering.

Final answer: Secondary xylem is not included in a bark.