What defines allelopathy in plants?

Allelopathy in plants refers to the phenomenon where one plant species releases chemical compounds, often called allelochemicals, into the environment, particularly into the soil, that can inhibit the growth of neighboring plants. This release of toxic substances can affect seed germination, plant growth, and overall health of competing species nearby. By utilizing these chemicals, a plant can reduce competition for resources, such as water and nutrients, thereby gaining an ecological advantage.

The other options focus on different aspects of plant interactions with their environment. Competition for sunlight describes a physical struggle for light between plants, which does not involve chemical interactions. The attraction of beneficial insects pertains to mutualistic relationships that can enhance pollination or pest control, rather than interference through chemical suppression. The use of nitrogen-fixing bacteria is a biological process that improves soil nutrient availability but is not related to allelopathy, which specifically involves the release of chemicals to inhibit others. Thus, the correct understanding of allelopathy is captured by the release of toxic substances into the soil.