Mycorrhizae play a vital role in ecosystems and material cycles. Which of the following statements best describes the ecological role of mycorrhizae and the nature of their relationship with host plants?
They act as primary decomposers, hydrolysing large insoluble organic molecules in the leaf litter layer to release phosphate ions directly into the plant's root xylem.
They fix atmospheric nitrogen gas directly within specialized fungal vesicles, bypassing the soil nitrogen cycle to supply the host plant with ammonium ions.
They vastly increase the surface area of the root system, facilitating the absorption of water and scarce mineral ions such as phosphate, in exchange for organic compounds.
They convert toxic nitrite ions in the rhizosphere into nitrate ions, protecting the root apical meristems from chemical inhibition.
