Final answer:
The symbiotic relationship between plant roots and fungi is known as mycorrhizae, a mutualistic association that enhances the nutrient and water intake of the plant while providing the fungus with carbohydrates. Option number 3 is correct.
Step-by-step explanation:
The symbiotic relationship between plant roots and fungi is called mycorrhizae. This mutualistic association is essential for the nutrient uptake and water absorption of many plants. The term mycorrhiza, which comes from the Greek words for fungus (myco) and root (rhizo), describes the fungi that colonize the roots of a host plant. This relationship is beneficial to both organisms: the plant receives enhanced access to water and minerals, while the fungus gains a constant supply of carbohydrates via the plant's photosynthesis. In soil with low nutrient concentration, low diffusion rate, or low moisture, mycorrhizae are particularly vital for plant survival.
There are different types of mycorrhizal relationships, including ectomycorrhizae and endomycorrhizae. It's important to distinguish mycorrhizae from lichen, which is another type of symbiosis involving a fungus and a photosynthetic partner, such as an alga or cyanobacterium.