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A parasitic plant is one that derives some or all of its nutritional requirements from another living plant. All parasitic plants have modified roots, named haustoria (singular: haustorium), which penetrate the host plants, connecting them to the conductive system - either the xylem, the phloem, or both. This provides them with the ability to extract water and nutrient from the hosts. About 4,100 species in approximately 19 families of flowering plants are known.〔Nickrent, D. L. and Musselman, L. J. 2004. Introduction to Parasitic Flowering Plants. ''The Plant Health Instructor''. ()〕 ==Classification== Parasitic plants are characterized as follows: *1a. Obligate parasite – a parasite that cannot complete its life cycle without a host. *1b. Facultative parasite – a parasite that can complete its life cycle independent of a host. *2a. Stem parasite – a parasite that attaches to the host stem. *2b. Root parasite – a parasite that attaches to the host root. *3a. Holoparasite – a plant that is completely parasitic on other plants and has virtually no chlorophyll. *3b. Hemiparasite – a plant that is parasitic under natural conditions and is also photosynthetic to some degree. Hemiparasites may just obtain water and mineral nutrients from the host plant. Many obtain at least part of their organic nutrients from the host as well. For hemiparasites, one from each of the three sets of terms can be applied to the same species, e.g. *''Nuytsia floribunda'' (Western Australian Christmas tree) is an obligate root hemiparasite. *''Rhinanthus'' (e.g. Yellow rattle) is a facultative root hemiparasite. *Mistletoe is an obligate stem hemiparasite. Holoparasites are always obligate so only two terms are needed, e.g. *Dodder is a stem holoparasite. *''Hydnora'' spp. are root holoparasites. Plants usually considered holoparasites include broomrape, dodder, ''Rafflesia'', and the Hydnoraceae. Plants usually considered hemiparasites include ''Castilleja'', mistletoe, Western Australian Christmas tree, and yellow rattle. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Parasitic plant」の詳細全文を読む スポンサード リンク
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