Illinois Pesticide Applicator Practice Test

What indicates a lack of nutrients in plants that may be observed as yellowing of leaves?

1. Anthracnose

2. Chlorosis

3. Hypoxia

4. Phytotoxicity

The correct answer is: Chlorosis

Chlorosis is the phenomenon characterized by the yellowing of leaves due to a lack of essential nutrients, primarily nitrogen, magnesium, or iron. In chlorosis, the chlorophyll production is impaired, resulting in the leaves losing their green color and turning yellow because chlorophyll is the pigment responsible for the green coloring in plants and essential for photosynthesis. This condition can arise from various factors, including nutrient deficiencies in the soil, poor soil pH, waterlogged soils, or certain diseases that affect a plant's ability to absorb nutrients. Recognizing chlorosis is crucial for the maintenance and health of plants, as it serves as an indicator that corrective action may be necessary, such as fertilization or improving soil conditions. Other options like anthracnose refer to a fungal disease affecting plants, hypoxia involves a deficiency of oxygen, particularly relevant in aquatic settings affecting root health, and phytotoxicity relates to plant injury caused by chemical exposure, which may not specifically cause yellowing as a direct sign of nutrient deficiency.