ISA Certified Arborist Practice Exam

What is the function of the phloem in a tree?

1. Transport water from roots

2. Store nutrients

3. Transport sugars and nutrients

4. Provide structural support

The correct answer is: Transport sugars and nutrients

The phloem is a vital tissue in plants, and its primary function is to transport sugars and nutrients produced during photosynthesis from the leaves to other parts of the tree, such as roots, stems, and developing fruits. The sugars, primarily in the form of sucrose, are essential for the energy needs of various plant cells and also play a crucial role in growth and development. This transport is bidirectional, meaning that it can move substances both upward and downward within the plant. In contrast, the other options highlight different functions that do not pertain to the phloem. For instance, water transport is primarily handled by the xylem, which carries water and dissolved minerals from the roots to the rest of the plant. Nutrient storage typically occurs in specialized tissues or organs, such as parenchyma cells or certain storage organs, rather than in the phloem. Lastly, providing structural support is mainly a function of the plant's wood, which is composed of xylem and other supportive tissues, not the phloem. Understanding the unique role of phloem within the context of the tree's overall physiology emphasizes its importance in maintaining healthy growth and metabolic functions.