![Cuscuta parasite plant](https://upload.wikimedia.org/wikipedia/commons/1/12/Cuscuta_parasite_plant.JPG)
A parasitic plant is a
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...
that derives some or all of its nutritional requirements from another living plant. They make up about 1% of
angiosperms
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants ...
and are found in almost every
biome
A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...
. All
parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
plants develop a specialized organ called the
haustorium
In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates th ...
, which penetrates the host plant, connecting them to the host vasculature – either the
xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...
,
phloem
Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is c ...
, or both.
For example, plants like ''
Striga
''Striga'', commonly known as witchweed, is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae, although older classifications place it in the Scrophul ...
'' or ''
Rhinanthus
''Rhinanthus'' is a genus of annual hemiparasitic herbaceous plants in the family Orobanchaceae, formerly classified in the family Scrophulariaceae. Its species are commonly known as rattles. The genus consists of about 30 to 40 species found in ...
'' connect only to the xylem, via xylem bridges (xylem-feeding). Alternately,
plants
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclude ...
like ''
Cuscuta
''Cuscuta'' (), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the ...
'' and some members of ''
Orobanche
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
'' connect to both the xylem and phloem of the host.
This provides them with the ability to extract water and nutrients from the host. Parasitic plants are classified depending on the location where the parasitic plant latches onto the host (root or stem), the amount of nutrients it requires, and their photosynthetic capability.
Some parasitic plants can locate their
host plants by detecting volatile
chemicals
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wit ...
in the air or soil given off by host
shoot
In botany, a plant shoot consists of any plant stem together with its appendages, leaves and lateral buds, flowering stems, and flower buds. The new growth from seed germination that grows upward is a shoot where leaves will develop. In the sp ...
s or
root
In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the su ...
s, respectively. About 4,500
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
of parasitic plants in approximately 20 families of
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s are known.
Classification
Parasitic plants occur in multiple plant families, indicating that the evolution is
polyphyletic
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
. Some families consist mostly of parasitic representatives such as
Balanophoraceae
The Balanophoraceae are a subtropical to tropical family of obligate parasitic flowering plants, notable for their unusual development and formerly obscure affinities. In the broadest circumscription, the family consists of 16 genera. Alternati ...
, while other families have only a few representatives. One example is the North American ''
Monotropa uniflora
''Monotropa uniflora'', also known as ghost plant, ghost pipe, or Indian pipe, is an herbaceous perennial plant native to temperate regions of Asia, North America, and northern South America, but with large gaps between areas. The plant is somet ...
'' (Indian pipe or corpse plant) which is a member of the heath family,
Ericaceae
The Ericaceae are a family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with c.4250 known species spread across 124 genera, making it th ...
, better known for its member blueberries, cranberries, and
rhododendrons
''Rhododendron'' (; from Ancient Greek ''rhódon'' "rose" and ''déndron'' "tree") is a very large genus of about 1,024 species of woody plants in the heath family (Ericaceae). They can be either evergreen or deciduous. Most species are nati ...
.
Parasitic plants are characterized as follows:
![Mistletoe, coming soon to a market near you - geograph](https://upload.wikimedia.org/wikipedia/commons/f/f1/Mistletoe%2C_coming_soon_to_a_market_near_you_-_geograph.org.uk_-_1585249.jpg)
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
''Rhinanthus'' is a genus of annual hemiparasitic herbaceous plants in the family Orobanchaceae, formerly classified in the family Scrophulariaceae. Its species are commonly known as rattles. The genus consists of about 30 to 40 species found in ...
'' (e.g.
Yellow rattle
''Rhinanthus minor'', known as yellow rattle, is a herbaceous wildflower in the genus '' Rhinanthus'' in the family Orobanchaceae (the broomrapes). It has circumpolar distribution in Europe, Russia, western Asia, and northern North America. An a ...
) is a facultative root hemiparasite.
*
Mistletoe is an obligate stem hemiparasite.
Holoparasites are always obligate so only two terms are needed, e.g.
*
Dodder
''Cuscuta'' (), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the ...
is a stem holoparasite.
*''
Hydnora'' spp. are root holoparasites.
Plants usually considered holoparasites include
broomrape
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
,
dodder
''Cuscuta'' (), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the ...
, ''
Rafflesia
''Rafflesia'' () is a genus of parasitic flowering plants in the family Rafflesiaceae. The species have enormous flowers, the buds rising from the ground or directly from the lower stems of their host plants; one species has the largest flowers i ...
'', and the
Hydnoraceae
Hydnoroideae is a subfamily of parasitic flowering plants in the order Piperales. Traditionally, and as recently as the APG III system it given family rank under the name Hydnoraceae. It is now submerged in the Aristolochiaceae. It contains two ge ...
. Plants usually considered hemiparasites include ''
Castilleja
''Castilleja'', commonly known as paintbrush, Indian paintbrush, or prairie-fire, is a genus of about 200 species of annual and perennial herbaceous plants native to the west of the Americas from Alaska south to the Andes, northern Asia, and on ...
'',
mistletoe,
Western Australian Christmas tree
''Nuytsia floribunda'' is a hemiparasitic tree found in Western Australia. The species is known locally as moodjar and, more recently, the Christmas tree or Western Australian Christmas tree. The display of intensely bright flowers during the ...
, and
yellow rattle
''Rhinanthus minor'', known as yellow rattle, is a herbaceous wildflower in the genus '' Rhinanthus'' in the family Orobanchaceae (the broomrapes). It has circumpolar distribution in Europe, Russia, western Asia, and northern North America. An a ...
.
Evolution of parasitism
![Striga root connections](https://upload.wikimedia.org/wikipedia/commons/a/aa/Striga_root_connections.jpg)
Parasitic behavior evolved in angiosperms roughly 12-13 times independently, a classic example of
convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
. Roughly 1% of all angiosperm species are parasitic, with a large degree of host dependence. The taxonomic family ''
Orobanchaceae
Orobanchaceae, the broomrapes, is a family of mostly parasitic plants of the order Lamiales, with about 90 genera and more than 2000 species. Many of these genera (e.g., ''Pedicularis'', ''Rhinanthus'', ''Striga'') were formerly included in th ...
'' (encompassing the genera ''
Triphysaria'', ''
Striga
''Striga'', commonly known as witchweed, is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae, although older classifications place it in the Scrophul ...
'', and ''
Orobanche
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
'') is the only family that contains both holoparasitic and hemiparasitic species, making it a model group for studying the evolutionary rise of
parasitism. The remaining groups contain only hemiparasites or holoparasites.
[Westwood, James H., John I. Yoder, Michael P. Timko, and Claude W. Depamphilis. "The Evolution of Parasitism in Plants." ''Trends in Plant Science'' 15.4 (2010) 227-35. Web.]
The evolutionary event which gave rise to parasitism in plants was the development of haustoria. The first, most ancestral, haustoria are thought to be similar to that of the facultative hemiparasites within ''
Triphysaria'', lateral haustoria develop along the surface of the roots in these species. Later evolution led to the development of terminal or primary haustoria at the tip of the juvenile
radicle
In botany, the radicle is the first part of a seedling (a growing plant embryo) to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil (the shoot emerges from ...
, seen in obligate hemiparasitic species within ''
Striga
''Striga'', commonly known as witchweed, is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae, although older classifications place it in the Scrophul ...
''. Lastly, holoparasitic plants, always forms of obligate parasites, evolved over the loss of photosynthesis, seen in the genus ''
Orobanche
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
''.
[
To maximize resources, many parasitic plants have evolved 'self-incompatibility', to avoid parasitizing themselves. Others such as '' Triphysaria'' usually avoid parasitizing other members of their species, but some parasitic plants have no such limits.][ The ]albino redwood
An albino' redwood is a redwood tree which is unable to produce chlorophyll, and has white needles instead of the normal green. It survives by obtaining sugar through the connections between its roots and those of neighboring normal redwood(s) ...
is a mutant ''Sequoia sempervirens
''Sequoia sempervirens'' ()''Sunset Western Garden Book,'' 1995:606–607 is the sole living species of the genus '' Sequoia'' in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast redwood, coastal ...
'' that produces no chlorophyll; they live on sugars from neighbouring trees, usually the parent tree from which they have grown (via a somatic mutation).
Seed germination
Parasitic plants germinate
Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...
in several methods. These can either be chemical or mechanical and the means used by seeds often depends on whether or not the parasites are root parasites or stem parasites. Most parasitic plants need to germinate near their host plants because their seeds are limited in the number of resources necessary to survive without nutrients from their host plants. Resources are limited due in part to the fact that most parasitic plants are not able to use autotrophic
An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Works", ...
nutrition to establish the early stages of seeding.[Scott, P. 2008. Physiology and behavior of plants: parasitic plants. John Wiley & sons pp. 103–112.][Runyon, J. Tooker, J. Mescher, M. De Moraes, C. 2009. Parasitic plants in agriculture: Chemical ecology of germination and host-plant location as targets for sustainable control: A review. Sustainable Agriculture Reviews 1. pp. 123-136.]
Root parasitic plant seeds tend to use chemical cues for germination. For germination to occur, seeds need to be quite close to the host plant.[ For example, the seeds of witchweed ('']Striga asiatica
''Striga asiatica'', the Asiatic witchweed or the red witchweed, is a parasitic plant, hemiparasitic plant in the family Orobanchaceae. It is native to Asia and sub-Saharan Africa, but has been introduced into other parts of the world including ...
'') need to be within 3 to 4 millimeters (mm) of its host to receive chemical signals in the soil to trigger germination. This range is important because ''Striga Asiatica'' will only grow about 4 mm after germination.[ Chemical compound cues sensed by parasitic plant seeds are from host plant root exudates that are leached nearby from the host's ]root system
In mathematics, a root system is a configuration of vectors in a Euclidean space satisfying certain geometrical properties. The concept is fundamental in the theory of Lie groups and Lie algebras, especially the classification and representatio ...
into the surrounding soil. These chemical cues are a variety of compounds that are unstable and rapidly degraded in soil and are present within a radius of a few meters of the plant exuding them. Parasitic plants germinate and follow a concentration gradient of these compounds in the soil toward the host plants if close enough. These compounds are called strigolactone Strigolactones are a group of chemical compounds produced by a plant's roots. Due to their mechanism of action, these molecules have been classified as plant hormones or phytohormones. So far, strigolactones have been identified to be responsible f ...
s. Strigolactone stimulates ethylene biosynthesis in seeds causing them to germinate.[
There are a variety of chemical germination stimulants. ]Strigol Strigolactones are a group of chemical compounds produced by a plant's roots. Due to their mechanism of action, these molecules have been classified as plant hormones or phytohormones. So far, strigolactones have been identified to be responsible fo ...
was the first of the germination stimulants to be isolated. It was isolated from a non-host cotton plant and has been found in true host plants such as corn and millets. The stimulants are usually plant-specific, examples of other germination stimulants include sorgolactone from sorghum, Orobanche and electoral from red clover, and 5-deoxystrigol from '' Lotus japonicus''. Strigolactones are apocarotenoids that are produced via the carotenoid pathway of plants. Strigolactones and mycorrhizal fungi have a relationship in which Strigolactone also cues the growth of mycorrhizal fungus.[
Stem parasitic plants, unlike most root parasites, germinate using the resources inside their endosperms and can survive for some time. For example, the dodders (''Cuscuta'' spp.) drop their seeds to the ground. These may remain dormant for up to five years before they find a host plant. Using the resources in the seed endosperm, the dodder can germinate. Once germinated, the plant has 6 days to find and establish a connection with its host plant before its resources are exhausted.][ Dodder seeds germinate above ground, then the plant sends out stems in search of its host plant reaching up to 6 cm before it dies. It is believed that the plant uses two methods of finding a host. The stem detects its host plant's scent and orients itself in that direction. Scientists used volatiles from ]tomato
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...
plants (α-pinene
α-Pinene is an organic compound of the terpene class, one of two isomers of pinene. It is an alkene and it contains a reactive four-membered ring. It is found in the oils of many species of many coniferous trees, notably the pine. It is also ...
, β-myrcene
Myrcene, or β-myrcene, is a monoterpene. A colorless oil, it occurs widely in essential oils. It is produced mainly semi-synthetically from '' Myrcia'', from which it gets its name. It is an intermediate in the production of several fragrances. ...
, and β-phellandrene) to test the reaction of '' C. pentagona'' and found that the stem orients itself in the direction of the odor.[ Some studies suggest that by using light reflecting from nearby plants dodders can select hosts with higher sugar because of the levels of chlorophyll in the leaves.][Lesica, P. 2010. Dodder: Hardly Doddering. Kelsey Newsletter of Montana Native Plant Society. Vol 23. 2, 6] Once the dodder finds its host, it wraps itself around the host plant's stem. Using adventitious roots, the dodder taps into the host plant's stem with a haustorium
In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates th ...
, an absorptive organ within the host plant vascular tissue
Vascular tissue is a complex conducting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue are the xylem and phloem. These two tissues transport fluid and nutrients internally. The ...
. Dodder makes several of these connections with the host as it moves up the plant.[
]
Seed dispersal
There are several methods of seed dispersal, but all the strategies aim to put the seed in direct contact with, or within a critical distance of, the host.
# The '' Cuscuta'' seedling can live for 3–7 days and extend out 35 cm in search of the host before it dies. This is because the ''Cuscuta'' seed is large and has stored nutrients to sustain its life. This is also useful for seeds that get digested by animals and are excreted.
# Mistletoe use a sticky seed for dispersal. The seed sticks to nearby animals and birds and then comes into direct contact with the host.
# '' Arceuthobium'' seeds have a similarly sticky seed as the mistletoe but they do not rely on animals and birds, they mainly disperse by fruit explosiveness. Once the seed makes contact with the host, rainwater can help position the seed in a suitable position.
# Some seeds detect and respond to chemical stimulations produced in the host's roots and start to grow towards the host.
Obstacles to host attachment
A parasitic plant has many obstacles to overcome to attach to a host. Distance from the host and stored nutrients are some of the problems, and the host's defenses are an obstacle to overcome. The first hurdle is penetrating the host since the host has systems to reinforce the cell wall by protein cross-linking so that it stops the parasitic progress at the cortex
Cortex or cortical may refer to:
Biology
* Cortex (anatomy), the outermost layer of an organ
** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain''
*** Motor cortex, the regions of the cerebral cortex i ...
of the host's roots. The second hurdle is the host's ability to secrete 440px
Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical ...
germination inhibitors. This prevents germination of the parasitic seed. The third hurdle is the host's ability to create a toxic
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
environment at the location where the parasitic plant attaches. The host secretes phenolic compounds into the apoplast
Inside a plant, the apoplast can mean the space outside of cell membranes, where material can diffuse freely; that is, the extracellular spaces.
''Apoplast '' can also refer especially to the continuum of cell walls of adjacent cells; fluid and ...
. This creates a toxic environment for the parasitic plant, eventually killing it. The fourth hurdle is the host's ability to ruin the tubercle
In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal.
In plants
A tubercle is generally a wart-like projection ...
using gums and gels or injecting toxins into the tubercle
In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal.
In plants
A tubercle is generally a wart-like projection ...
.
Host range
Some parasitic plants are generalists and parasitize many different species, even several different species at once. Dodder (''Cuscuta
''Cuscuta'' (), commonly known as dodder or amarbel, is a genus of over 201 species of yellow, orange, or red (rarely green) parasitic plants. Formerly treated as the only genus in the family Cuscutaceae, it now is accepted as belonging in the ...
'' spp.) and red rattle (''Odontites vernus
''Odontites vernus'', the red bartsia, is a wild flower from the family Orobanchaceae native to Europe and Asia and occurring as an alien in North America. The red bartsia is a common plant in low-fertility soils, where it lives partially as a p ...
'') are generalist parasites. Other parasitic plants are specialists that parasitize a few or just one species. Beech drops ('' Epifagus virginiana'') is a root holoparasite only on American beech (''Fagus grandifolia
''Fagus grandifolia'', the American beech or North American beech, is a species of beech tree native to the eastern United States and extreme southeast of Canada.
Description
''Fagus grandifolia'' is a large deciduous tree growing to tall, w ...
''). ''Rafflesia
''Rafflesia'' () is a genus of parasitic flowering plants in the family Rafflesiaceae. The species have enormous flowers, the buds rising from the ground or directly from the lower stems of their host plants; one species has the largest flowers i ...
'' is a holoparasite on the vine ''Tetrastigma''. Plants such as ''Pterospora
''Pterospora'', commonly known as pinedrops, woodland pinedrops, Albany beechdrops, or giant bird's nest is a North American genus in the subfamily Monotropoideae of the heath family, and includes only the species ''Pterospora andromedea''. ...
'' become parasites of mycorrhizal
A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the pla ...
fungi. There is evidence that parasites also practice self-discrimination, species of '' Triphysaria'' experience reduced haustorium development in the presence of other ''Triphysaria''. The mechanism for self-discrimination in parasites is not yet known.[
]
Aquatic parasitic plants
Parasitism also evolved within aquatic species of plants and algae. Parasitic marine plants are described as benthic, meaning that they are sedentary or attached to another structure. Plants and algae that grow on the host plant, using it as an attachment point are given the designation epiphytic
An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...
( epilithic is the name given to plants/algae that use rocks or boulders for attachment), while not necessarily parasitic, some species occur in high correlation with a certain host species, suggesting that they rely on the host plant in some way or another. In contrast, endophytic
An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; h ...
plants and algae grow inside their host plant, these have a wide range of host dependence from obligate holoparasites to facultative hemiparasites.
Marine parasites occur as a higher proportion of marine flora in temperate rather than tropical waters. While no full explanation for this is available, many of the potential host plants such as kelp
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms.
Kelp grows in "underwa ...
and other macroscopic brown algae
Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and p ...
are generally restricted to temperate areas. Roughly 75% of parasitic red algae infect hosts in the same taxonomic family as themselves, these are given the designation adelphoparasites. Other marine parasites, deemed endozoic, are parasites of marine invertebrates ( mollusks, flatworms, sponge
Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...
s) and can be either holoparasitic or hemiparasitic, some retaining the ability to photosynthesize after infection.[
]
Importance
Species within ''Orobanchaceae
Orobanchaceae, the broomrapes, is a family of mostly parasitic plants of the order Lamiales, with about 90 genera and more than 2000 species. Many of these genera (e.g., ''Pedicularis'', ''Rhinanthus'', ''Striga'') were formerly included in th ...
'' are some of the most economically destructive species on Earth. Species of ''Striga
''Striga'', commonly known as witchweed, is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae, although older classifications place it in the Scrophul ...
'' alone are estimated to cost billions of dollars a year in crop yield loss annually, infesting over 50 million hectares of cultivated land within sub-Saharan Africa alone. ''Striga
''Striga'', commonly known as witchweed, is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is currently classified in the family Orobanchaceae, although older classifications place it in the Scrophul ...
'' can infest both grasses and grains, including corn, rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
and sorghum, some of the most important food crops. ''Orobanche
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
'' also threatens a wide range of important crops, including peas, chickpeas
The chickpea or chick pea (''Cicer arietinum'') is an annual legume of the family Fabaceae, subfamily Faboideae. Its different types are variously known as gram" or Bengal gram, garbanzo or garbanzo bean, or Egyptian pea. Chickpea seeds are hi ...
, tomatoes
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...
, carrots, lettuce
Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae. It is most often grown as a leaf vegetable, but sometimes for its stem and seeds. Lettuce is most often used for salads, although it is also seen in other kinds of food, ...
, and varieties of the genus ''Brassica
''Brassica'' () is a genus of plants in the cabbage and mustard family ( Brassicaceae). The members of the genus are informally known as cruciferous vegetables, cabbages, or mustard plants. Crops from this genus are sometimes called ''cole c ...
'' (e.g. cabbage and broccoli). Yield loss from ''Orobanche
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
'' can reach 100% and has caused farmers in some regions of the world to abandon certain staple crops and begin importing others as an alternative. Much research has been devoted to the control of ''Orobanche'' and ''Striga'' species, which are even more devastating in developing areas of the world, though no method has been found to be entirely successful.[
*Mistletoes cause economic damage to forests and ornamental trees.
*'']Rafflesia arnoldii
''Rafflesia arnoldii'', the corpse flower or giant padma, is a species of flowering plant in the parasitic genus ''Rafflesia''. It is noted for producing the largest individual flower on Earth. It has a strong and unpleasant odor of decaying ...
'' produces the world's largest flowers at about one meter in diameter. It is a tourist attraction in its native habitat.
*Sandalwood
Sandalwood is a class of woods from trees in the genus ''Santalum''. The woods are heavy, yellow, and fine-grained, and, unlike many other aromatic woods, they retain their fragrance for decades. Sandalwood oil is extracted from the woods for us ...
trees (''Santalum'' species) have many important cultural uses and their fragrant oils have high commercial value.
*Indian paintbrush ('' Castilleja linariaefolia'') is the state flower of Wyoming
Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...
.
*The oak mistletoe ('' Phoradendron serotinum'') is the floral emblem of Oklahoma.
*A few other parasitic plants are occasionally cultivated for their attractive flowers, such as ''Nuytsia
''Nuytsia floribunda'' is a hemiparasitic tree found in Western Australia. The species is known locally as moodjar and, more recently, the Christmas tree or Western Australian Christmas tree. The display of intensely bright flowers during the ...
'' and broomrape
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
.
*Parasitic plants are important in research, especially on the loss of photosynthesis and the co-dependency of functional, genetic and lifestyle changes.
*A few dozen parasitic plants have occasionally been used as food by people.
*Western Australian Christmas tree ('' Nuytsia floribunda'') sometimes damages underground cables. It mistakes the cables for host roots and tries to parasitize them using its sclerenchymatic guillotine.
Some parasitic plants are destructive while some have positive influences in their communities. Some parasitic plants damage invasive species more than native species
In biogeography, a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution (though often popularised as "with no human intervention") during history. The term is equ ...
. This results in the reduced damage of invasive species in the community.
In many regions, including the Nepal
Nepal (; ne, :ne:नेपाल, नेपाल ), formerly the Federal Democratic Republic of Nepal ( ne,
सङ्घीय लोकतान्त्रिक गणतन्त्र नेपाल ), is a landlocked country in S ...
Eastern Himalayas
]
The Eastern Himalayas extend from eastern Nepal across Northeast India, Bhutan, the Tibet Autonomous Region to Yunnan in China and northern Myanmar. The climate of this region is influenced by the monsoon of South Asia from June to September. ...
, parasitic plants are used for medicinal and ritual purposes.
Plants parasitic on fungi
About 400 species of flowering plants, plus one gymnosperm
The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...
(''Parasitaxus usta
''Parasitaxus usta'' is a rare species of conifer of the family Podocarpaceae, and the sole species of the genus ''Parasitaxus''. It is a woody shrub up to 1.8 m found only in the remote, densely forested areas of New Caledonia, first discovered ...
''), are parasitic on mycorrhizal fungi. This effectively gives these plants the ability to become associated with many of the other plants around them. They are termed myco-heterotrophs. Some myco-heterotrophs are Indian pipe (''Monotropa uniflora
''Monotropa uniflora'', also known as ghost plant, ghost pipe, or Indian pipe, is an herbaceous perennial plant native to temperate regions of Asia, North America, and northern South America, but with large gaps between areas. The plant is somet ...
''), snow plant ('' Sarcodes sanguinea''), underground orchid ('' Rhizanthella gardneri''), bird's nest orchid (''Neottia nidus-avis
''Neottia nidus-avis'', the bird's-nest orchid, is a non-photosynthetic orchid, native to Europe, Russia and some parts of the Middle East.
Description
''Neottia nidus-avis'' grows to tall and each shoot can carry up to 60 flowers. Plants ar ...
''), and sugarstick ('' Allotropa virgata''). Within the taxonomic family ''Ericaceae
The Ericaceae are a family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with c.4250 known species spread across 124 genera, making it th ...
'', known for extensive mycorrhizal relationships, there are the Monotropoids. The Monotropoids include the genera ''Monotropa
''Monotropa'' is a genus of three species of herbaceous perennial flowering plants that were formerly classified in the family Monotropaceae and presently are classified in Ericaceae. They are native to temperate regions of the Northern Hemisph ...
'', ''Monotropsis
''Monotropsis'' is a monotypic genus of plants containing the single species ''Monotropsis odorata'', also known as sweet pinesap or pygmy pipes. It is a member of the subfamily Monotropoideae of the family Ericaceae.
It is found in the states of ...
'', and ''Pterospora
''Pterospora'', commonly known as pinedrops, woodland pinedrops, Albany beechdrops, or giant bird's nest is a North American genus in the subfamily Monotropoideae of the heath family, and includes only the species ''Pterospora andromedea''. ...
'' among others. Myco-heterotrophic behavior is commonly accompanied by the loss of chlorophyll.[Judd, Walter S., Christopher Campbell, and Elizabeth A. Kellogg. ''Plant Systematics: A Phylogenetic Approach''. Sunderland, MA: Sinauer Associates, 2008. Print.]
References
External links
*
The International Parasitic Plant Society
{{Authority control
Plant physiology