Illinois Pesticide Applicator Practice Test

The yellowish-green coloration observed in normally green plant tissues is known as chlorosis. This condition occurs when there is a deficiency in chlorophyll, which is the pigment responsible for the green color in plants and plays a crucial role in photosynthesis. When chlorophyll production is hindered due to factors such as nutrient deficiencies (commonly nitrogen, iron, or magnesium), poor drainage, or root damage, the plant tissues lose their vibrant green color and appear yellowish-green.

In contrast, photosynthesis deficiency typically refers to a broader issue that may not specifically manifest as yellowing leaves, as it can result from inadequate light or other environmental stresses. Pest damage does not inherently cause chlorosis; rather, it may result in visible damage from feeding or tunneling that could lead to stress but does not always change the green color directly. Excess fertilization can lead to nutrient burn or toxicity, but it does not directly cause the chlorosis that results from nutrient deficiencies. Thus, the physiological condition described is specifically identified as chlorosis.