What is Haustoria?

Haustoria Meaning: The name derives from the Latin word haustor, which means "one who draws, drains, or drinks," and refers to the activity carried out by the outgrowth. A haustorium (plural haustoria) is a root-like structure that grows into or around another structure to absorb water or nutrients in botany and mycology. The structure of mistletoe and members of the broomrape family, for example, penetrates the tissue of the host and extracts nutrients from it. It is the appendage or part of a parasitic fungus (the hyphal tip) that serves a similar role in mycology.

Haustoria Definition Biology: The knob-like root structure that parasitic angiosperms use to penetrate the host plant is referred to as the haustorium. It acts as a feeding organ for the host plant, absorbing nutrients and water.


The haustorium is a fungus cell or tissue projection that absorbs nutrients and water in fungal species. A hyphal projection enters the cytoplasm of a host plant cell.

What are Haustorial Roots?

Sucking or Haustorial Roots ā€“ These roots are found in parasitic plants. Both xylem and phloem tissues can be found in haustorial roots. These slender roots penetrate the host plant's xylem and phloem, allowing them to absorb water, minerals, and food. Parasites develop adventitious roots from the stem which penetrate into the tissue of the host plant and suck nutrients. Examples: Cuscuta (dodder), Cassytha, Orobanche (broomrape), Viscum (mistletoe), Dendrophthoe.

Haustoria in Cuscuta

Cuscuta (dodder) is a genus of over 201 parasitic plants that are yellow, orange, (rarely green) in colour. It is also known in India as Amar bail. On the basis of the work of the Angiosperm Phylogeny Group, it is now recognised as belonging to the morning glory family, Convolvulaceae, after previously being regarded as the only genus in the Cuscutaceae family. The genus is present worldwide in temperate and tropical climates, with the greatest species diversity in subtropical and tropical climates; however, the genus is uncommon in cool temperate climates, with only four species native to northern Europe.

Dodder wraps itself around a plant after it has attached itself to it. If the host contains food that is beneficial to the dodder, the dodder will develop haustoria or haustorial roots that will enter the host's vascular system. The dodder's initial root in the soil then dies. The dodder has the ability to develop and bind to several plants. It can grow more or less continuously in tropical areas and reach high into the canopy of shrubs and trees; however, it is an annual plant in cold temperate regions and is restricted to relatively low vegetation that can be reached by new seedlings each spring.

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Fungal Haustoria

Haustoria are formed by fungi from all major divisions. Haustoria comes in a variety of shapes and sizes. In general, when a fungus penetrates the plasma membrane of a host, it releases enzymes that break down the cell walls, allowing more organic carbon to be transferred from the host to the fungus. As a result, an insect infected with a parasitic fungus-like Cordyceps may appear to be "eating from the inside out" as the haustoria extends inside it.

Small spheres are the most basic haustoria. The largest are complex formations that expand between the cell wall and the cell membrane, adding substantial mass to a cell. The entire fungus may become enclosed in the cell in the Chytridiomycota, and whether this should be considered equivalent to a haustorium is debatable.

Intercellular hyphae, appressoria, and external hyphae are all sources of haustoria. As it passes through the cell wall, the hypha narrows before expanding and invaginating the cell. At the point of invagination, a thickened, electron-dense collar of material is deposited around the hypha. In the invaginated region, the host cell wall is also heavily modified. There are no inclusions in the plasma membrane, and the outer layer contains more polysaccharide. Both partners' walls have been severely weakened.

Within the haustorial complex, the functional exchange takes place. The fungus receives organic carbon from the host, and metabolic activity within the complex is much higher than outside. The fungus absorbs carbon from the host and transports it to the rest of the thallus. The host plant appears to be responding to the fungus's signals, and the complex appears to be under the invader's influence.

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FAQs (Frequently Asked Questions)

1. What is the Function of Haustoria?

Ans) The haustorium is a tube that penetrates the host's tissues and absorbs nutrients and water. The haustoria of parasitic plants like dodder and mistletoe form a vascular union with the host plant to redirect the nutrients.

2. What Type of Fungi has Haustoria?

Ans) Rust fungi are biotrophic fungi that can be identified by the rust-coloured pustules of spores that appear on their hosts. These fungi are highly specialised, attacking only certain plant species or strains. They can be destructive cereal pathogens, severely limiting grain production.

3. What is the Haustoria Embryo Sac?

Ans) The embryo sac is nourished by antipodals, which have a nutritive function. Antipodal cells produce substances that aid in the growth and production of the endosperm. Haustoria forms primarily at the chalazal end of the chalazal and enters nuclear tissue to absorb nutrients.