Tree rings are formed when .......... alternates with .........

Options

A. Alburnum, duramen
B. Protoxylem, metaxylem
C. Early wood, late wood
D. Heartwood, sapwood

Answer

To answer the question "Tree rings are formed when .......... alternates with .........", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Tree Rings**: Tree rings, also known as annual rings, are formed in the cross-section of a tree trunk. Each ring represents one year of growth.

2. **Identifying the Components**: Tree rings consist of two main types of wood formed during different seasons of growth:
- **Early Wood**: This is formed during the favorable growing season when conditions are optimal for growth. It is characterized by lighter color and less dense tissue.
- **Late Wood**: This is formed during the unfavorable season when growth slows down, leading to denser and darker tissue due to increased deposition of secondary substances.

3. **Alternation of Early and Late Wood**: Each year, as the seasons change, the tree produces early wood in the spring and late wood in the summer or fall. This alternation results in the formation of distinct rings.

4. **Conclusion**: Therefore, we can conclude that tree rings are formed when **early wood alternates with late wood**.

### Final Answer:
Tree rings are formed when **early wood alternates with late wood**.

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