Read an Academic Passage

[1]Most land plants live in partnership with fungi. Thin fungal threads called hyphae wrap around or grow into a plant's roots and spread far into the surrounding soil. This relationship, known as a mycorrhiza, is extremely old: fossils show that it existed more than 400 million years ago, when plants first began to grow on land.

[2]The partnership benefits both sides. Hyphae are much thinner than roots, so they can reach into tiny spaces between soil particles and absorb water and minerals, especially phosphorus, that the plant could not reach on its own. In return, the plant supplies the fungus with sugars it makes through photosynthesis. Because fungi cannot photosynthesize, many species depend entirely on this supply.

[3]In forests, the hyphae of one fungus may connect the roots of several trees at once. Some researchers have reported that carbon and nutrients pass through these networks from large trees to young seedlings growing in the shade. This idea has attracted wide public interest, but other scientists caution that the evidence comes from a small number of studies and that the amounts transferred may be too small to matter.