Certified Arborist Practice Exam

Under what condition do trees take up essential elements through the roots?

1. Dissolved in water

2. Injected below the absorbing roots

3. Wilting, marginal burning, dieback

4. Fertilizer salts causing symptoms

The correct answer is: Dissolved in water

Trees primarily take up essential elements through their roots when those elements are dissolved in water. This process is fundamental to nutrient uptake because roots absorb nutrients from the soil solution, which is made up of water containing dissolved minerals and organic matter. For a nutrient to be bioavailable for the tree, it must be soluble in water, as this is how roots interact with the nutrient-rich environment in the soil. While injecting nutrients below the absorbing roots can provide nutrients directly to the tree, it does not represent the natural mechanism by which most nutrition is taken up. Similarly, conditions like wilting, marginal burning, and dieback, as well as fertilizer salts causing symptoms, refer to stress or damage signs rather than optimal conditions for nutrient uptake. They do not directly address the process of absorption but rather indicate potential problems with nutrient availability or uptake by the tree.