A 50 years old tree with distinct annual rings in its trunk will show.

Options

A. 50 annual rings from base of trunk to apex
B. 50 rings at base of trunk and about 20 rings at apex.
C. 50 rings at its base of trunk and uniformly decreasing towards apex
D. 50 rings at base of trunk and more or irregular number of rings at apex.

Answer

**Step-by-Step Text Solution:**

1. **Understanding Annual Rings**: Annual rings, also known as growth rings, are formed in the trunk of a tree due to the activity of the cambium layer. This layer is responsible for the secondary growth of the plant, which increases its girth.

2. **Cambial Activity**: The cambium is a layer of actively dividing cells located between the xylem (wood) and phloem (bark). It divides to produce new xylem cells towards the inside and new phloem cells towards the outside.

3. **Seasonal Growth Patterns**: The growth of the tree occurs in cycles, primarily influenced by seasonal changes. During the spring season, when resources are abundant, the cambium divides rapidly, producing larger xylem cells with wide lumens. This is referred to as "spring wood."

4. **Autumn Growth**: In contrast, during the autumn season, the availability of resources decreases, leading to slower cambial activity. The xylem cells produced during this time are smaller and have narrower lumens, known as "autumn wood."

5. **Formation of Annual Rings**: Each year, the combination of spring wood and autumn wood forms one complete annual ring. Therefore, a tree that is 50 years old will have 50 distinct annual rings.

6. **Visual Representation**: The annual rings can be visually observed as concentric circles in the cross-section of the trunk. Each ring represents one year of growth, with the spring wood being thicker and lighter in color, and the autumn wood being thinner and darker.

7. **Conclusion**: Thus, a 50-year-old tree will show a total of 50 annual rings, which will be consistent in thickness from the base to the apex of the trunk, with the spring wood being thicker than the autumn wood.