Plant-fungi research. Light micrograph of a petri dish culture of a plant and the fungi associated with its roots. The thicker strands are the roots, and the thinner ones are the hyphae. Fungal spore-producing areas (round dots) are also seen. This research involves arbuscular mycorrhizal (AM) fungi, an an example of mycorrhizal symbiosis. These fungi are mutualistic symbionts living in the roots of many land plant species. Extensive underground fungal networks connect the roots of different plants and are essential for the uptake of soil nutrients and their transfer to the host plants.