Certified Crop Advisor Practice Exam

What term describes the phenomenon when a plant produces a chemical toxin that impairs the growth of another plant?

1. Mutualism

2. Commensalism

3. Allelopathy

4. Parasitism

The correct answer is: Allelopathy

The term that describes the phenomenon when a plant produces a chemical toxin that impairs the growth of another plant is allelopathy. This biological interaction involves one plant releasing allelochemicals into the environment, which can inhibit or promote growth in neighboring plants. These chemicals can come from various parts of the plant, including roots, leaves, and even decaying plant material, and their effects can range from growth inhibition to outright toxicity. In agricultural contexts, understanding allelopathy is important because it can influence crop success, weed management, and biodiversity within ecosystems. Some farmers may strategically use allelopathic plants to suppress weeds and enhance crop yields by reducing competition for resources. The other options describe different types of ecological interactions: mutualism involves beneficial relationships between species, commensalism refers to a situation where one species benefits while the other is neither helped nor harmed, and parasitism denotes a relationship where one species benefits at the expense of another. These concepts do not capture the mechanism of chemical inhibition that characterizes allelopathy.