What is the function of haustoria in parasitic fungi?

Haustoria play a crucial role in the lifestyle of parasitic fungi by facilitating the absorption of nutrients from their host organisms. These specialized structures penetrate the tissues of the host and establish a direct interface through which the fungus can extract water, carbohydrates, and other essential nutrients needed for its growth and reproduction. This nutrient uptake is essential for the survival of the parasitic fungus, as it relies entirely on the host's resources for sustenance.

The other functions referenced in the other options do not pertain to haustoria. Dispersing spores is typically performed by other structures such as spore-bearing bodies, not haustoria. Anchoring into the substrate is a general function of the fungal mycelium, while aiding reproduction is usually associated with reproductive structures rather than haustoria, which are specialized for nutrient absorption. Therefore, the primary function of haustoria is correctly identified as the absorption of nutrients from the host.