Certified Professional Horticulturist (CPH) Practice Exam

Which three non-mineral elements do plants primarily use?

1. Carbon, Hydrogen, Oxygen

2. Nitrogen, Phosphorus, Potassium

3. Argon, Oxygen, Hydrogen

4. Calcium, Phosphorus, Hydrogen

The correct answer is: Carbon, Hydrogen, Oxygen

Plants primarily utilize carbon, hydrogen, and oxygen as essential non-mineral elements. These elements are fundamental for the process of photosynthesis, where carbon dioxide, absorbed from the atmosphere, is combined with water (which consists of hydrogen and oxygen) to produce glucose and oxygen. Carbon is a critical building block for carbohydrates, proteins, and lipids, while hydrogen and oxygen are integral to various biochemical processes and cellular structures. In contrast, the other options include elements that are primarily mineral nutrients (like nitrogen, phosphorus, and potassium), which play different roles mostly related to plant growth, metabolism, and cellular function, but they do not fall into the non-mineral category that comprises the basic building blocks provided by carbon, hydrogen, and oxygen. Thus, the option highlighting carbon, hydrogen, and oxygen accurately identifies the key non-mineral elements that plants depend on for fundamental metabolic processes.