Certified Arborist Practice Exam

Trees that have grown in dense shade such as a forest tend to have long, straight stems with little what?

1. Cellulose

2. Potential for failure

3. Reaction wood

4. Root collar excavation

The correct answer is: Reaction wood

Trees that have grown in dense shade, such as those in a forest, tend to develop long, straight stems with little reaction wood. Reaction wood is a type of wood that trees produce in response to mechanical stress or uneven growth conditions, helping them maintain stability and resist bending under weight or wind. In shaded environments, trees grow tall and straight in a competitive struggle for sunlight, minimizing the need for reaction wood that would otherwise develop to counteract any lean or imbalance. When trees are exposed to direct sunlight, they may grow more asymmetrically or at angles due to wind or other environmental factors, thus increasing their structural challenges, necessitating the formation of reaction wood. The absence of significant natural stress in shaded growth leads to the predominance of straight, elongated stems without the need for this structural adaptation. This is critical for understanding tree physiology and how environmental conditions influence growth patterns in different settings.