Mycorrhizal fungi primarily assist plants by which function?

• A. Providing photosynthesis for the plant
• B. Protecting leaves from sunburn
• C. Extending the root network to improve water and nutrient uptake
• D. Fixing atmospheric nitrogen into usable forms

Answer: (C)

Mycorrhizal fungi form a partnership with plant roots to greatly expand the area the plant can explore for water and nutrients. Their hyphae reach far into the soil, increasing the effective root surface area and helping the plant access water and minerals (especially phosphorus and micronutrients) that are often outside the root’s reach. In return, the plant supplies the fungi with sugars from photosynthesis. This exchange enhances nutrient and water uptake and can improve drought tolerance and soil structure through the fungal network. The other options don’t fit because photosynthesis occurs in the plant’s leaves, not in fungi; protecting leaves from sunburn isn’t a function of mycorrhizal associations; and nitrogen fixation is carried out by certain bacteria, not by mycorrhizal fungi.