haustoria

Haustorium, plural haustoria, is a specialized feeding organ produced by certain parasitic plants and plant-pathogenic fungi that enables the parasite to connect with a host's tissues and extract water, minerals, and sometimes sugars. It arises as a growth from the parasite and differentiates into a tip that can penetrate host tissues.

In parasitic plants, haustoria form at points where the shoot or root contacts a host plant. The haustorial tip penetrates the host’s outer layers and contacts vascular tissues such as xylem and/or phloem. Xylem-feeding haustoria primarily obtain water and minerals, while phloem connections can allow transfer of sugars. The haustorium often contains transfer cells to increase surface area for solute transport and may involve enzymatic remodeling of host cell walls.

In fungi and some oomycetes, haustoria are specialized hyphal structures that invade host tissue to form a feeding interface. They typically invaginate the host cell plasma membrane and establish an extrahaustorial contact, through which nutrients are absorbed. Haustoria are common in biotrophic pathogens such as rusts, powdery mildews, and downy mildews, where they play a central role in nutrient uptake and interaction with host defenses.

Ecological and agricultural importance: Haustoria are central to the biology of many parasitic plants and plant pathogens. They influence host range, disease progression, and crop yield, making them a focus of research for controlling parasitic weeds and fungal diseases.