Haustorium

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Haustorium" – news · newspapers · books · scholar · JSTOR (May 2007) (Learn how and when to remove this template message)

The etymology of the name corresponds to the Latin word haustor meaning the one who draws, drains or drinks,^[2][3] and refers to the action performed by the outgrowth.

In fungi

Fungi in all major divisions form haustoria. Haustoria take several forms. Generally, on penetration, the fungus increases the surface area in contact with host plasma membrane releasing enzymes that break up the cell walls, enabling greater potential movement of organic carbon from host to fungus. Thus, an insect hosting a parasitic fungus such as Cordyceps may look as though it is being "eaten from the inside out" as the haustoria expand inside of it.^{[citation needed]}

The simplest forms of haustoria are small spheres. The largest are complex formations adding significant mass to a cell, expanding between the cell wall and cell membrane. In the Chytridiomycota, the entire fungus may become enclosed in the cell, and it is arguable whether this should be considered analogous to a haustorium.^{[citation needed]}

Haustoria arise from intercellular hyphae,

Functional exchange takes place within the haustorial complex. The host supplies organic carbon to the fungus, and the metabolic activity within the complex is considerably greater than outside. Carbon from the host is absorbed by the fungus, and transported to the rest of the thallus. The host plant appears to be functioning according to signals from the fungus and the complex appears to be under the control of the invader.^[4]

The haustorium may be mycelium or root-shaped.^{[citation needed]}

In plants

Mistletoes (including Loranthaceae and Viscaceae) attach to their hosts via a haustorium. The haustoria attacks the host's xylem and/or phloem and attaches itself to the host.^[5] This structure both anchors the mistletoe, and taps into the host plant. Mistletoes use passive mechanisms to draw water from their hosts. They keep their leaf stomata open night and day which sets up a moisture gradient between mistletoe and host.^[6]

A second meaning of 'haustorium' in botany is to describe tissues in a developing plant embryo that transfer nutrients from the seed's endosperm to the embryo. These tissues are found widely in the seeds of flowering plants.^[7]

References