What is the main function of the haustorium in parasitic fungi?

The main function of the haustorium in parasitic fungi is to absorb nutrients from a host's tissues. This specialized structure allows the fungus to penetrate the host cells and create a direct interface for nutrient exchange. By forming these connections, the haustorium effectively taps into the host's cellular resources, extracting vital nutrients necessary for the growth and reproduction of the fungus. This adaptation is critical for the survival of parasitic fungi, as they rely exclusively on their host for sustenance.

The other choices, while related to fungal biology, do not accurately describe the primary role of the haustorium. The formation of spores is a separate reproductive process, structural support provided by mycelium involves different fungal structures, and the movement of spores pertains to dispersal mechanisms not connected to haustorial function.