Annual or growth rings consist of -

Options

A. Alternate rings of heart and early wood
B. Alternate rings of sapwood and heart wood
C. Alternate rings of early and late wood
D. Alternate rings of porous and non-porous wood

Answer

**Step-by-Step Solution:**

1. **Understanding Annual Rings**: Annual rings, also known as growth rings, are the layers of wood produced by the cambium layer of a tree. Each year, a tree adds a new layer of growth, which can be observed as rings in a cross-section of the trunk.

2. **Cambium Activity**: The cambium is a layer of actively dividing cells that contribute to the growth of the tree. Its activity is not uniform throughout the year; it varies with the seasons.

3. **Types of Wood Produced**:
- During the spring and early summer, the cambium is more active, producing a larger number of xylem vessels with wider cavities. This results in lighter-colored wood, known as **early wood** or **spring wood**.
- In contrast, during late summer and autumn, the cambium is less active, producing fewer xylem vessels with narrower cavities, resulting in darker-colored wood known as **late wood** or **autumn wood**.

4. **Formation of Growth Rings**: Each year, the tree produces one layer of early wood and one layer of late wood. Therefore, the annual rings consist of alternating layers of these two types of wood.

5. **Conclusion**: Based on the explanation above, the correct answer to the question "Annual or growth rings consist of" is **C: alternate rings of early and late wood**.

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