ISA Certified Arborist Practice Exam 2025 – All-in-One Resource for Comprehensive Exam Success!

The primary function of tree leaves is to photosynthesize and produce food for the tree. During photosynthesis, leaves convert sunlight into chemical energy by using carbon dioxide from the air and water from the soil. This process produces glucose, which serves as food for the tree, enabling it to grow and develop.

Leaves contain chlorophyll, the pigment responsible for capturing sunlight, and they have specialized structures called chloroplasts where photosynthesis occurs. This process is essential not only for the tree's functioning but also for the ecosystem, as it contributes to the oxygen we breathe.

While providing shade is a benefit of having leaves, the critical role they play is in food production. Storage of water and nutrients, and the strengthening of the trunk and branches, are not primary functions of leaves but rather involve different parts of the tree system, such as roots for nutrient storage and the structural integrity provided by the trunk and branches.