
A parasitic plant is a
plant
Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
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 (). The term angiosperm is derived from the Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed within a fruit. T ...
and are found in almost every
biome
A biome () is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. In 1935, Tansley added the ...
. All
parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...
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 (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...
,
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 ...
, 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 parasitic plant, 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 ...
'' connect only to the xylem, via xylem bridges (xylem-feeding). Alternately,
plants
Plants are the eukaryotes that form the kingdom Plantae; they are predominantly photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars f ...
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 almost 200 species of small Parasitic plant, parasitic herbaceous plants, mostly native to the temperate climate, temperate Northern Hemisphere. It is the type genus of the Orobanchaceae ...
'' connect to both the xylem and phloem of the host.
This provides them with the ability to extract resources from the host. These resources can include water, nitrogen, carbon and/or sugars.
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
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
* Host Island, in the Wilhelm Archipelago, Antarctica
People
* ...
plants by detecting volatile
chemicals
A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...
in the air or soil given off by host
shoot
Shoot most commonly refers to:
* Shoot (botany), an immature plant or portion of a plant
* Shooting, the firing of projectile weapons
* Photo shoot, a photography session; an event wherein a photographer takes photographs
Shoot may also refer t ...
s or
root
In vascular plants, the roots are the plant organ, 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 bel ...
s, respectively. About 4,500
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of parasitic plants in approximately 20 families of
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...
s are known.
There is a wide range of effects that may occur to a host plant due to the presence of a parasitic plant. Often there is a pattern of stunted growth in hosts especially in hemi-parasitic cases, but may also result in higher mortality rates in host plant species following introduction of larger parasitic plant populations.
Classification
Parasitic plants occur in multiple plant families, indicating that the evolution is
polyphyletic
A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
. 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. Alterna ...
, while other families have only a few representatives. One example is the North American ''
Monotropa uniflora'' (Indian pipe or corpse plant) which is a member of the heath family,
Ericaceae
The Ericaceae () are a Family (biology), 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 about 4,250 known species spread acros ...
, better known for its member blueberries, cranberries, and
rhododendrons.
Parasitic plants are characterized as follows:
For hemiparasites, one from each of the three sets of terms can be applied to the same species, e.g.
*''
Nuytsia floribunda
''Nuytsia floribunda'' is a Hemiparasite, 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 flowe ...
'' (Western Australian Christmas tree) is an obligate root hemiparasite.
*''
Rhinanthus
''Rhinanthus'' is a genus of annual parasitic plant, 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 ...
'' (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 an ...
) is a facultative root hemiparasite.
*
Mistletoe
Mistletoe is the common name for obligate parasite, obligate parasitic plant, hemiparasitic plants in the Order (biology), order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they ...
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 almost 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae. It is a weed on ...
,
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'' (), or stinking corpse lily, is a genus of Parasitic plants, 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 p ...
'', and the
Hydnoraceae
Hydnoroideae is a subfamily of holoparasitism, 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. I ...
. 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 plant, annual and Perennial plant, perennial mostly herbaceous plants native to the west of the Americas from Alaska sout ...
'',
mistletoe
Mistletoe is the common name for obligate parasite, obligate parasitic plant, hemiparasitic plants in the Order (biology), order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they ...
,
Western Australian Christmas tree, 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 an ...
.
Evolution of parasitism
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 comm ...
. 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 (biology), family of mostly parasitic plants of the order (biology), order Lamiales, with about 90 genus, genera and more than 2000 species. Many of these genera (e.g., ''Pedicularis'', ''Rhinanthus'', ...
'' (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 almost 200 species of small Parasitic plant, parasitic herbaceous plants, mostly native to the temperate climate, temperate Northern Hemisphere. It is the type genus of the Orobanchaceae ...
'') is the only family that contains both holoparasitic and hemiparasitic species, making it a model group for studying the evolutionary rise of
parasitism
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...
. The remaining groups contain only hemiparasites or holoparasites.
The evolutionary event which gave rise to parasitism in plants was the development of
haustoria
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 ...
. 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 t ...
, 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 almost 200 species of small Parasitic plant, parasitic herbaceous plants, mostly native to the temperate climate, temperate Northern Hemisphere. It is the type genus of the Orobanchaceae ...
''.
[ The most specialized forms of holoparasitic plants are the four families ]Rafflesiaceae
The Rafflesiaceae are a family of rare parasitic plants comprising 36 species in 3 genera found in the tropical forests of east and southeast Asia, including ''Rafflesia arnoldii'', which has the largest flowers of all plants. The plants are e ...
, Cytinaceae, Mitrastemonaceae and Apodanthaceae, lineages which independently has evolved further into endoparasites that, except for the flowers, spend their entire life cycle within the tissue of their host.
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 is a mutant '']Sequoia sempervirens
''Sequoia sempervirens'' ()''Sunset Western Garden Book,'' 1995: 606–607 is the sole living species of the genus ''Sequoia (genus), Sequoia'' in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast ...
'' 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 flowering plant, angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the sp ...
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 is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms. Autotrophs produce complex organic compounds (such as carbohydrates, fats, and proteins) us ...
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 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 Australia and th ...
'') 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 vector space, 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 ...
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 roots of plants. 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 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 endosperm is a tissue produced inside the seeds of most of the flowering plants following double fertilization. It is triploid (meaning three chromosome sets per nucleus) in most species, which may be auxin-driven. It surrounds the Embryo#Pla ...
, the dodder can germinate. Once germinated, the plant has six 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 (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible Berry (botany), berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originate ...
plants ( α-pinene, β-myrcene, and β-phellandrene
Phellandrenes are organic compounds with the formula . They have a similar molecular structure and similar chemical properties. α-Phellandrene and β-phellandrene are cyclic terpene, monoterpenes and are double-bond isomers. In α-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
Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...
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 transporting 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. T ...
. 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
Mistletoe is the common name for obligate parasite, obligate parasitic plant, hemiparasitic plants in the Order (biology), order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they ...
use a sticky seed for dispersal. The seed sticks to nearby animals and birds and then comes into direct contact with the host.
# ''Arceuthobium
The genus ''Arceuthobium'', commonly called dwarf mistletoes, is a genus of 42 species of parasitic plants that parasitize members of Pinaceae and Cupressaceae in North America, Central America, Asia, Europe, and Africa. Of the 42 species that h ...
'' 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
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 mec ...
germination inhibitors. This prevents germination
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, ...
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 subst ...
environment at the location where the parasitic plant attaches. The host secretes phenolic compounds into the apoplast
The ''apoplast '' is the extracellular space outside of plant cell membranes, especially the fluid-filled cell walls of adjacent cells where water and dissolved material can flow and diffuse freely. Fluid and material flows occurring in any extr ...
. 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 projectio ...
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 projectio ...
.
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'') 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
Beech (genus ''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to subtropical (accessory forest element) and temperate (as dominant element of mesophytic forests) Eurasia and North America. There are 14 accepted species i ...
''). ''Rafflesia
''Rafflesia'' (), or stinking corpse lily, is a genus of Parasitic plants, 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 p ...
'' is a holoparasite on the vine ''Tetrastigma''. Plants such as '' Pterospora'' become parasites of mycorrhizal
A mycorrhiza (; , 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 plant's rhizosphere, the plant root system and its surroundings. Mycorrhizae play ...
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
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
, 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 a plant or plant-like organism that grows on the surface of another 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 epiphyt ...
( 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 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 or seaweeds that make up the order (biology), order Laminariales. There are about 30 different genus, genera. Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a str ...
and other macroscopic brown algae
Brown algae (: alga) are a large group of multicellular algae comprising the class (biology), class Phaeophyceae. They include many seaweeds located in colder waters of the Northern Hemisphere. Brown algae are the major seaweeds of the temperate ...
are generally restricted to temperate areas. Roughly 75% of parasitic red algae
Red algae, or Rhodophyta (, ; ), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest Phylum, phyla of algae, containing over 7,000 recognized species within over 900 Genus, genera amidst ongoing taxon ...
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
Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...
, flatworm
Platyhelminthes (from the Greek language, Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a Phylum (biology), phylum of relatively simple bilaterian, Segmentation (biology), ...
s, sponge
Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...
s) and can be either holoparasitic or hemiparasitic, some retaining the ability to photosynthesize after infection. These are the only parasitic plants that parasitize animal hosts.[
]
Importance
Species within ''Orobanchaceae
Orobanchaceae, the broomrapes, is a family (biology), family of mostly parasitic plants of the order (biology), order Lamiales, with about 90 genus, genera and more than 2000 species. Many of these genera (e.g., ''Pedicularis'', ''Rhinanthus'', ...
'' 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
Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...
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
Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout Poaceae, grass that produces cereal grain. It was domesticated by indigenous peoples of Mexico, indigenous peoples in southern Mexico about 9,000 years ago ...
, rice
Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...
and sorghum
''Sorghum bicolor'', commonly called sorghum () and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a species in the Poaceae, grass genus ''Sorghum (genus), Sorghum'' cultivated for its grain. The grain i ...
, some of the most important food crops. ''Orobanche
''Orobanche'', commonly known as broomrape, is a genus of almost 200 species of small Parasitic plant, parasitic herbaceous plants, mostly native to the temperate climate, temperate Northern Hemisphere. It is the type genus of the Orobanchaceae ...
'' 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, cultivated for its edible seeds. Its different types are variously known as gram," Bengal gram, garbanzo, garbanzo bean, or Egypt ...
, tomatoes
The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originated from and was d ...
, carrot
The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in colour, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild ...
s, lettuce
Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae mostly grown as a leaf vegetable. The leaves are most often used raw in Green salad, green salads, although lettuce is also seen in other kinds of food, such as sandwiche ...
, 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, mustard plants, or simply brassicas. Crops from this genus are sometim ...
'' (e.g. cabbage and broccoli). Yield loss from ''Orobanche
''Orobanche'', commonly known as broomrape, is a genus of almost 200 species of small Parasitic plant, parasitic herbaceous plants, mostly native to the temperate climate, temperate Northern Hemisphere. It is the type genus of the Orobanchaceae ...
'' 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, Its local name is Petimum Sikinlili. It is a species of flowering plant in the parasitic genus '' Rafflesia'' within the family Rafflesiaceae. It is noted for producing the largest in ...
'' 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. Sanda ...
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 landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...
.
*The oak mistletoe ('' Phoradendron serotinum'') is the floral emblem of Oklahoma
Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
.
*A few other parasitic plants are occasionally cultivated for their attractive flowers, such as '' Nuytsia'' and broomrape
''Orobanche'', commonly known as broomrape, is a genus of almost 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae. It is a weed on ...
.
*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
''Nuytsia floribunda'' is a Hemiparasite, 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 flowe ...
'') 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
A community is a Level of analysis, social unit (a group of people) with a shared socially-significant characteristic, such as place (geography), place, set of Norm (social), norms, culture, religion, values, Convention (norm), customs, or Ide ...
. Some parasitic plants damage invasive species
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
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 equi ...
. This results in the reduced damage of invasive species
An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
in the community. Parasitic plants are major shapers of their community, affecting not just the host species but indirectly affecting others. Competition amongst host species will change due to the parasitic plant. Plant parasitism have been shown to keep invasive species under control and become keystone species in an ecosystem.
In many regions, including the Nepal
Nepal, officially the Federal Democratic Republic of Nepal, is a landlocked country in South Asia. It is mainly situated in the Himalayas, but also includes parts of the Indo-Gangetic Plain. It borders the Tibet Autonomous Region of China Ch ...
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. I ...
, parasitic plants are used for medicinal and ritual purposes.
Plants parasitic on fungi
About 400 species of flowering plants, plus one gymnosperm
The gymnosperms ( ; ) are a group of woody, perennial Seed plant, seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include Pinophyta, conifers, cycads, Ginkgo, and gnetoph ...
('' Parasitaxus usta'') and one bryophyte
Bryophytes () are a group of embryophyte, land plants (embryophytes), sometimes treated as a taxonomic Division (taxonomy), division referred to as Bryophyta ''Sensu#Common qualifiers, sensu lato'', that contains three groups of non-vascular pla ...
(the liverwort
Liverworts are a group of non-vascular land plants forming the division Marchantiophyta (). They may also be referred to as hepatics. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry ...
'' Aneura mirabilis''), 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''), 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, with sporadic presence in North-Africa, and some parts of the Middle East.
Description
''Neottia nidus-avis'' grows to tall and each sh ...
''), and sugarstick ('' Allotropa virgata''). Within the taxonomic family ''Ericaceae
The Ericaceae () are a Family (biology), 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 about 4,250 known species spread acros ...
'', known for extensive mycorrhizal relationships, there are the Monotropoids. The Monotropoids include the genera '' Monotropa'', ''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'' 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.]
See also
* Living stump
References
External links
*
The International Parasitic Plant Society
{{Authority control
Plant physiology