Red Seal Landscape Horticulturist Practice Exam

Which three macronutrients are essential for plant growth?

1. Carbon, hydrogen, and sulfur

2. Nitrogen, phosphorus, and potassium

3. Calcium, magnesium, and iron

4. Oxygen, sodium, and manganese

The correct answer is: Nitrogen, phosphorus, and potassium

The three macronutrients essential for plant growth are nitrogen, phosphorus, and potassium. These nutrients play critical roles in various physiological and biochemical processes within plants. Nitrogen is vital for the synthesis of amino acids and nucleic acids, which are the building blocks of proteins and DNA, respectively. This nutrient is crucial for the overall growth of plants, as it contributes to the formation of chlorophyll, which is necessary for photosynthesis. Phosphorus is important for energy transfer within the plant, being a key component of ATP (adenosine triphosphate). It also plays a significant role in root development and flowering. Adequate phosphorus levels promote strong root systems and enhance a plant's ability to absorb other nutrients. Potassium is essential for regulating various plant metabolic processes, including water uptake, enzyme activation, and photosynthesis. It helps maintain turgor pressure, which is important for the structure and stabilization of plant tissues. Together, these three macronutrients are often referred to as N-P-K, based on their chemical symbols, and are commonly found in fertilizers to support healthy plant growth and development. Understanding the importance of nitrogen, phosphorus, and potassium is fundamental for any landscape horticulturist, as these nutrients are critical in promoting