ISA Certified Arborist Practice Exam 2026 – All-in-One Resource for Comprehensive Exam Success!

Stomata are small pores found on the leaves of a tree. They are responsible for gas exchange, allowing the tree to take in carbon dioxide for photosynthesis and release oxygen and water vapor. Stomata play a crucial role in regulating the tree's transpiration, which is the process of water loss through the leaves. Therefore, the correct answer is D, Leaves.

Stomata are not typically found in the roots, branches, or trunk of a tree. While all parts of a tree are important for various functions, stomata specifically serve their purpose on the leaves.