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

The essential macronutrients for tree growth include nitrogen, phosphorus, and potassium. Each of these elements plays a vital role in various physiological processes within the tree.

Nitrogen is crucial for foliage development and is a key component of amino acids, which are the building blocks of proteins. It is also involved in chlorophyll production, which is essential for photosynthesis, allowing the tree to convert sunlight into energy.

Phosphorus is important for energy transfer and storage in the form of ATP (adenosine triphosphate), which is vital for growth and development. It also plays a critical role in root development and the establishment of healthy plant cells.

Potassium is essential for regulating various physiological responses in trees, including water uptake and enzyme activation. It helps enhance disease resistance and improves overall plant health.

In contrast, while calcium and sulfur (as in the first choice) are important, they are classified as secondary nutrients rather than primary macronutrients. Similarly, magnesium plays a supporting role in plant health, but it is also not categorized as a primary macronutrient. Iron, manganese, and zinc (the last option) are classified as micronutrients and, while important in smaller quantities, do not have the same macro-level functions as the primary