What role do secondary metabolites play in plants?

Secondary metabolites play a crucial role in plants primarily as a defense mechanism against herbivores and pathogens. These compounds, which include alkaloids, terpenoids, and phenolics, are not directly involved in the fundamental processes of growth and development, like photosynthesis or nutrient absorption. Instead, they serve various ecological functions that enhance a plant's survival and reproduction.

For instance, many secondary metabolites have toxic or deterrent properties that can inhibit feeding by herbivores, making plants less palatable or even poisonous. Others might have antimicrobial properties that help protect the plant from diseases caused by bacteria, fungi, and viruses. In this way, secondary metabolites contribute significantly to a plant's ability to withstand biotic stress, ultimately improving its chances of survival in a competitive environment.

While secondary metabolites can also play roles in attracting pollinators or participating in complex interactions within their ecosystems, their primary and most studied function is in defense against threats from herbivores and pathogens. This defensive strategy illustrates the importance of chemical diversity in plant ecology and the specialized adaptations that plants have evolved over time.