FFA Floriculture Practice Test

What deficiency is indicated when a plant's leaves turn a dark to reddish color?

1. Potassium

2. Nitrogen

3. Phosphorus

4. Calcium

The correct answer is: Phosphorus

The dark to reddish coloration of a plant's leaves is typically indicative of a phosphorus deficiency. Phosphorus is essential for several key processes in plants, including energy transfer, photosynthesis, and nutrient movement within the plant. When plants lack sufficient phosphorus, older leaves often exhibit a purple to reddish tint due to the accumulation of anthocyanin pigments, which can be a response to stress from inadequate phosphorus levels. This color change serves as a visible sign that the plant is unable to perform its functions optimally. In contrast, potassium deficiency usually results in leaf margin burn and yellowing, nitrogen deficiency typically causes overall yellowing of the plant, particularly in older leaves, while calcium deficiency often leads to edge necrosis and growth deformities, particularly in new leaves. Therefore, recognizing the specific symptoms associated with nutrient deficiencies can aid in accurately diagnosing and addressing the health of plants.