Parasitic Plant

parasitic plant, plant that obtains all or part of its nutrition from another plant (the host) without contributing to the benefit of the host and, in some cases, causing extreme damage to the host. The defining structural feature of a parasitic plant is the haustorium, a specialized organ that penetrates the host and forms a vascular union between the plants.

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Parasitic plants differ from plants such as climbing vines, lianas, epiphytes, and aerophytes; though the latter are supported by other plants, they are not parasitic, because they use other plants simply as a structure on which to grow rather than as a direct source of water or nutrients. Another group of plants that is sometimes confused with parasites is the mycoheterotrophs. Similar to parasitic plants, mycoheterotrophs may lack chlorophyll and photosynthetic capacity, but they live in symbiotic association with fungi that gain nutrition from autotrophic (self-feeding) plants or decaying vegetation. Such plants are not classified as parasitic, because they do not appear to harm the fungi and they lack haustoria.

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All parasitic plant species are angiosperms, among which parasitism has evolved independently about 12 times. Some examples of parasitic angiosperm families include Balanophoraceae, Orobanchaceae, and Rafflesiaceae. Although one species of gymnosperm, Parasitaxus usta, has been proposed to be parasitic, it actually may be a mycoheterotroph as it appears to involve a fungal symbiont.