What organism forms a symbiotic relationship with tree roots to increase the tree's uptake of water and essential elements?

• A. Hyphae
• B. Mycorrhizae
• C. Bacteria
• D. Lichens

Answer: (B)

The key idea is the mutualistic partnership between tree roots and fungi, called mycorrhizae. Fungal hyphae form an extensive network that spreads far into the soil, greatly increasing the root system’s surface area for absorbing water and nutrients, especially immobile nutrients like phosphorus. In return for access to the tree’s sugars produced by photosynthesis, the fungus supplies these absorbed water and nutrients to the tree. This relationship boosts the tree’s ability to take up water and essential elements and can also enhance drought resilience. While bacteria can form beneficial plant partnerships, they don’t create the same root-extending network as mycorrhizal fungi, and hyphae are filaments of fungi rather than a separate organism. Lichens involve a fungal partner with algae or cyanobacteria but not tree roots, so they don’t explain this root–fungus collaboration.