noun, countable. plural is haustoria. Related adjective is haustorial

A haustorium is the organ through which a parasitic plant is attached to a host plant. It attaches itself to the host and then penetrates the host conductive tissues. It serves as a form of root for the parasite, forming a physiological bridge through which nutrients pass from the host to the parasite. It is the defining feature of parasitic plants. Haustoria may take the form of either a primary or secondary haustorium.

examples

1. the sieve tube connection from the haustorium of the holoparasite
2. This paper discusses the mechanisms of haustorium penetration
3. Evidence of pectinase activity released by Orobanche haustorium in host tissues
4. the intrusion of the haustorium inside host tissues
5. haustorium development is also under control of biological molecular signals

Collocation - haustorium may be used as a modifier as in haustorium development, haustorium penetration or haustorium size, but is usually modified itself. The following examples show whether the haustorium is active or has failed functional, abortive haustorium or give its age young, mature haustorium

1. resistance occurred during the establishment of a functional haustorium
2. secretion was found along the abortive haustorium
3. the transformation of a young haustorium into a functional haustorium
4. the mature haustorium of Scleropyrum

Haustorium is often associated with certain verbs

• develop example - The haustorium develops when intrusive cells of the parasite penetrate host tissues
• form example - The germ tube develops and forms a haustorium
• invade example - The changes in cell wall composition persist long after the haustorium has penetrated
• penetrate Haustoria penetrate host tissues.
• attach The host stem where the dodder haustoria are attached

primary haustorium

The primary haustorium is a haustorium that develops at the apex of the young root that emerges from the parasite seed. It attaches itself to the host root before penetrating the host tissues and seeking the conductive elements located inside the host root .

examples

1. Striga penetrates the host tissue by developing primary and secondary haustoria.
2. The primary haustorium displays few such features.

secondary haustorium

Secondary haustoria may develop laterally from the primary root system of the parasite or on adventitious roots developing from parasite shoots. These provide further contact between the host roots, or branches in the case of aerial parasites such as mistletoe, and the parasite. This is particularly true in facultative parasites that do not have a primary haustorium. In some cases secondary haustoria allow the parasite to be attached to more than one host.

examples

1. secondary haustoria develop from the primary root system of the parasite.
2. the secondary haustoria are borne on the adventitious root system of Alectra vogelli.

haustorial

adjective haustorial. Related noun is haustorium

The adjective haustorial is often used to talk of the physiological aspect, haustorial cells, the process of formation and attachment, haustorial initiation, haustorial penetration, or the place of attachment, haustorial interface

examples

1. haustorial cells penetrate mainly the large vessels.
2. important stages of germination and haustorial initiation.
3. hypersensitive reactions that block haustorial penetration.
4. the most important structures of the haustorial interface.