Mycorrhiza, coloured scanning electron micrograph (SEM). A mycorrhiza is a symbiotic association between a soil fungus and the roots of a vascular plant. The majority of vascular plants roots are mycorrhizal. Here fungal hyphae (thin threads, orange) are seen both on the surface of, and within, the root. Both organisms benefit from this association. The fungus is able to access nutrient forms unavailable to the plant, process them and pass them on to the roots. The mass of hyphae also provide a large surface area for uptake of water and minerals. The fungus receives carbon compounds that the plant produces via photosynthesis. Magnification: x140 when printed at 10 centimetres wide.