USA Biology Olympiad (USABO) Practice Exam

In "ring porous wood," where are the vessels typically found?

1. In the summer wood

2. In the outer bark

3. In the spring wood

4. Throughout the entire growth ring

The correct answer is: In the spring wood

In "ring porous wood," the vessels are typically found in the spring wood, which is the early growth phase of a tree during the growing season. This type of wood exhibits a distinct growth pattern where larger vessels are formed during the spring when water and nutrients are plentiful, allowing for fast growth. As the season progresses into summer, the growth rate slows down and smaller vessels are formed in the summer wood. The anatomical structure of ring porous wood creates a clear differentiation between the spring and summer wood, with the large vessels of the spring wood allowing for efficient water transport during the critical growth period. This adaptation is crucial for the tree's health and growth, particularly in regions that experience seasonal variations in water availability. Thus, the correct answer highlights the specific location within the growth ring where these prominent vessels are concentrated.