Certified Professional Horticulturist (CPH) Practice Exam

Which of the following are primary nutrients considered essential for plant growth?

1. Nitrogen, Potassium, Calcium

2. Nitrogen, Phosphorus, Potassium

3. Nitrogen, Potassium, Magnesium

4. Nitrogen, Phosphorus, Calcium

The correct answer is: Nitrogen, Phosphorus, Potassium

The primary nutrients essential for plant growth, known as macronutrients, include nitrogen, phosphorus, and potassium. These elements play crucial roles in various physiological processes of plants. Nitrogen is vital for the synthesis of amino acids, the building blocks of proteins, as well as nucleic acids, which are essential for DNA and RNA. As a result, it significantly impacts plant growth and development, influencing leaf and stem growth. Phosphorus is needed for energy transfer through ATP (adenosine triphosphate) and is fundamental for root development, flowering, and seed production. It also plays a key role in photosynthesis and respiration. Potassium, while not part of proteins or nucleic acids, is essential for various physiological functions, including regulation of stomatal opening, enzyme activation, and balancing of plant water usage. While calcium and magnesium are also important nutrients, they fall into secondary and micronutrient categories rather than being classified as primary nutrients. Therefore, nitrogen, phosphorus, and potassium are recognized as the foundational elements that directly support robust plant growth, making this choice the correct response.