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

Cellulose is a complex carbohydrate composed of long chains of glucose molecules, and it serves as a fundamental building block for the cell walls of plants, including trees. Its significance lies in providing structural support and rigidity, which allows trees to maintain their shape and withstand various environmental stresses such as wind and gravity. The strength of cellulose contributes to the overall integrity of trees, enabling them to grow tall and sustain large canopies.

Other options may refer to important aspects of plant biology, but they do not accurately describe cellulose's primary role. For example, while nutrients are essential for photosynthesis, cellulose is not a nutrient but rather a structural polysaccharide. Enzymes are indeed crucial for plant growth but are different entities that facilitate biochemical reactions rather than structural components. Protective barriers against pathogens are typically formed by other substances, such as lignin and phenolic compounds, rather than cellulose itself. Therefore, understanding cellulose’s role in providing structural support highlights its importance in the life and health of trees.