Editing Parasitism (section)

=== Plants ===

{{main|Parasitic plant}}

[[File:Cuscuta parasite plant.JPG|thumb|left|upright|''[[Cuscuta]]'' (a dodder), a stem [[holoparasite]], on an [[acacia]] tree]]

A [[hemiparasite]] or ''partial parasite'' such as [[mistletoe]] derives some of its nutrients from another living plant, whereas a [[obligate parasite|holoparasite]] such as ''[[Cuscuta]]'' derives all of its nutrients from another plant.<ref name="Rastogi">{{cite book |last1=Rastogi |first1=V. B. |title=Modern Biology |url=https://books.google.com/books?id=D-85x6Jhji0C&q=partial+parasite&pg=SA1-PA115 |publisher=Pitambar Publishing |date=1997 |isbn=978-81-209-0496-5 |page=115}}</ref> [[Parasitic plant]]s make up about one per cent of [[angiosperms]] and are in almost every [[biome]] in the world.<ref name="Kokla Melnyk 2010">{{Cite journal |last1=Kokla |first1=Anna |last2=Melnyk |first2=Charles W. |date=1 October 2018 |title=Developing a thief: Haustoria formation in parasitic plants |journal=Developmental Biology |language=en |volume=442 |issue=1 |pages=53–59 |doi=10.1016/j.ydbio.2018.06.013 |pmid=29935146 |s2cid=49394142 |issn=0012-1606|doi-access= }}</ref><ref name="Heide-Jørgensen, H. 2008">{{cite book |last=Heide-Jørgensen |first=Henning S. |year=2008 |title=Parasitic flowering plants |publisher=Brill |isbn=978-90-04-16750-6}}</ref><ref name=Nickrent2002>{{cite web |last1=Nickrent |first1=Daniel L. |author-link1=Daniel Lee Nickrent |title=Parasitic Plants of the World |url=http://nickrentlab.siu.edu/NickrentPDFs/Chapter2.pdf |date=2002 |access-date=10 April 2018 |url-status=live |archive-url=https://web.archive.org/web/20160306062557/http://nickrentlab.siu.edu/NickrentPDFs/Chapter2.pdf |archive-date=6 March 2016}} which appeared in Spanish as Chapter 2, pp. 7–27 in: J. A. López-Sáez, P. Catalán and L. Sáez [eds.], ''Parasitic Plants of the Iberian Peninsula and Balearic Islands''.</ref> All these plants have modified roots, [[haustorium|haustoria]], 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 nutrients from the host. A parasitic plant is classified depending on where it latches onto the host, either the stem or the root, and the amount of nutrients it requires. Since holoparasites have no [[chlorophyll]] and therefore cannot make food for themselves by [[photosynthesis]], they are always obligate parasites, deriving all their food from their hosts.<ref name="Heide-Jørgensen, H. 2008"/> Some parasitic plants can locate their [[host (biology)|host]] plants by detecting [[Chemical substance|chemicals]] in the air or soil given off by host [[Shoot (botany)|shoot]]s or [[root]]s, respectively. About 4,500 [[species]] of parasitic plant in approximately 20 [[Family (biology)|families]] of [[flowering plant]]s are known.<ref name="Heide-Jørgensen, H. 2008"/><ref name="NickrentMusselman2004">{{cite journal |last1=Nickrent |first1=D. L. |last2=Musselman |first2=L. J. |title=Introduction to Parasitic Flowering Plants |journal=The Plant Health Instructor |year=2004 |doi=10.1094/PHI-I-2004-0330-01}}</ref>

Species within the ''[[Orobanchaceae]]'' (broomrapes) are among the most economically destructive of all plants. Species of ''[[Striga]]'' (witchweeds) are estimated to cost billions of dollars a year in crop yield loss, infesting over 50&nbsp;million hectares of cultivated land within Sub-Saharan Africa alone. ''Striga'' infects both grasses and grains, including [[Zea mays|corn]], [[Oryza sativa|rice]], and [[sorghum]], which are among the world's most important food crops. ''[[Orobanche]]'' also threatens a wide range of other important crops, including [[peas]], [[Cicer arietinum|chickpeas]], [[Solanum lycopersicum|tomatoes]], [[carrot]]s, and varieties of [[cabbage]]. Yield loss from ''Orobanche'' can be total; despite extensive research, no method of control has been entirely successful.<ref name="WestwoodYoder2010">{{cite journal |last1=Westwood |first1=James H. |last2=Yoder |first2=John I. |last3=Timko |first3=Michael P. |last4=dePamphilis |first4=Claude W. |title=The evolution of parasitism in plants |journal=Trends in Plant Science |volume=15 |issue=4 |year=2010 |pages=227–235 |doi=10.1016/j.tplants.2010.01.004|pmid=20153240 |bibcode=2010TPS....15..227W }}</ref>

Many [[plants]] and [[fungi]] exchange carbon and nutrients in mutualistic [[mycorrhizal]] relationships. Some 400 species of [[myco-heterotrophy|myco-heterotrophic]] plants, mostly in the tropics, however effectively [[Cheating (biology)|cheat]] by taking carbon from a fungus rather than exchanging it for minerals. They have much reduced roots, as they do not need to absorb water from the soil; their stems are slender with few [[vascular bundle]]s, and their leaves are reduced to small scales, as they do not photosynthesize. Their seeds are small and numerous, so they appear to rely on being infected by a suitable fungus soon after germinating.<ref>{{cite journal |last=Leake |first=J. R. |date=1994 |title=The biology of myco-heterotrophic ('saprophytic') plants |journal=New Phytologist |volume=127 |issue=2 |pages=171–216 |doi=10.1111/j.1469-8137.1994.tb04272.x|pmid=33874520 |bibcode=1994NewPh.127..171L |s2cid=85142620 }}</ref>

[[File:Armillaria mellea, Honey Fungus, UK 1.jpg|thumb|The honey fungus, ''[[Armillaria mellea]]'', is a parasite of trees, and a [[saprophyte]] feeding on the trees it has killed.]]