Which term best describes the relationship between trees and mycorrhizal fungi?

• A. Symbiotic
• B. Parasitic
• C. Predatory
• D. Commensal

Answer: (A)

The relationship is symbiotic. Mycorrhizal fungi form a close association with tree roots where both partners benefit: the fungi expand the tree’s access to water and nutrients (especially phosphorus) through their extensive hyphal network, while the tree supplies carbohydrates produced by photosynthesis to the fungi. This mutual exchange is the hallmark of a symbiotic relationship. It isn’t parasitic, since the tree gains from the association; it isn’t commensal, since the tree also benefits; and it isn’t predatory, which involves one organism capturing and consuming another.