''Cassytha'' is a genus of some two dozen species of
obligately 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 has c ...
vine
A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners themselv ...
s in the family
Lauraceae
Lauraceae, or the laurels, is a plant family that includes the true laurel and its closest relatives. This family comprises about 2850 known species in about 45 genera worldwide (Christenhusz & Byng 2016 ). They are dicotyledons, and occur ma ...
. Superficially, and in some aspects of their ecology, they closely resemble plants in the unrelated genus ''
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 ...
'', the dodders.
[Weber, J. Z. A TAXONOMIC REVISION OF CASSYTHA (LAURACEAE) IN AUSTRALIA. J. Adelaide Bot. Gard. 3(3): 187-262(1981]
JSTOR
/ref> When fruit and flowers are absent in the field, the physical resemblance is so close that few people without technical training can discern the difference. In this respect and in their ecology the two genera present a spectacular 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 ...
.[Nickrent, D. L. 2002. Phylogenetic Origins of Parasitic Plants. Chapter 3, pp. 29-56 In J. A. López-Sáez, P. Catalán and L. Sáez ds. Parasitic Plants of the Iberian Peninsula and Balearic Islands. Mundi-Prensa, Madrid.] Nonetheless, Nickrent comments that "''Cassytha'' is uneqivocally assigned to Lauraceae
Lauraceae, or the laurels, is a plant family that includes the true laurel and its closest relatives. This family comprises about 2850 known species in about 45 genera worldwide (Christenhusz & Byng 2016 ). They are dicotyledons, and occur ma ...
based on (both) morphological and molecular data."[The Parasitic Plant Connection: Phylogenetic Relationships of Parasitic Flowering Plants]
/ref>[ In its divergence from ]habits
A habit (or wont as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. typical of the Lauraceae, ''Cassytha'' also presents examples of mosaic evolution
Mosaic evolution (or modular evolution) is the concept, mainly from palaeontology, that evolutionary change takes place in some body parts or systems without simultaneous changes in other parts. Another definition is the "evolution of characters ...
Several species of ''Cassytha'' are regarded as pests in various regions, though as a rule they are not as serious a problem as the true dodders. Some even yield a welcome harvest of fruit, or are valued for their perceived medicinal or aphrodisiac properties, partly because, like many members of the Lauraceae, some are fragrant when bruised. Their stems make useful strings for construction of thatched roofs and certain styles of lei and the like.
Common names and confusion
Probably the most useful common name
In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...
s for ''Cassytha'' species are laurel dodder or dodder laurel, because they look like dodder and are fragrant members of the laurel
Laurel may refer to:
Plants
* Lauraceae, the laurel family
* Laurel (plant), including a list of trees and plants known as laurel
People
* Laurel (given name), people with the given name
* Laurel (surname), people with the surname
* Laurel (mus ...
family, Lauraceae
Lauraceae, or the laurels, is a plant family that includes the true laurel and its closest relatives. This family comprises about 2850 known species in about 45 genera worldwide (Christenhusz & Byng 2016 ). They are dicotyledons, and occur ma ...
. The name love vine has merit because some species, in particular ''C. filiformis'', are regarded as aphrodisiacs in the Caribbean
The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
region.[Esbaugh, W. Hardy; McClure, Susan A. & Bolyard, Judith L. Bush Medicine Studies, Andros Island, Bahamas. Proceedings of the first symposium on the botany of the Bahamas 11–14 June 1985. Ed. Robert R. Smith., San Salvador, Bahamas.]
In practice, the confusion between the various species of ''Cassytha'' and ''Cuscuta'' is so unavoidable that their common names are more or less interchangeable. Practically all the common names for dodder accordingly are widely applied in error to ''Cassytha'' as well, but as a matter of convenience in Florida at least, where members of both groups of plants are present as agricultural pests, a publication of the Department of Agriculture adopts the names woe vine for ''Cassytha'' and dodder for ''Cuscuta''.[Haynes, Alan R., Coile, Nancy C., Schubert. Timothy S.; "Comparison of Two Parasitic Vines: Dodder (Cuscuta) and Woe Vine (Cassytha)". Botany Circular No. 30. Fla. Dept Agric. & Consumer Services January/February 1996. Division of Plant Industry]
Context and distribution
Though the Lauraceae constitute a large family, with thousands of species in tens of genera, ''Cassytha'' is its only known parasitic genus, and its climbing habit also is atypical of the family; most Lauraceae are woody shrubs or trees. The genus at one time was assigned its own family, Cassythaceae, but currently agreement on its inclusion into the Lauraceae is general.[
As currently defined, ''Cassytha'' has a wide distribution for a genus of so few species. Most are native to Australia (including temperate regions, where they are the only native members of the family), but a few are indigenous to Africa, southern Asia, various islands, and regions in the Americas. Some species seem to have been spread inadvertently by humans and probably by birds as well, and now occur on several continents. ''C. filiformis'', for example, grows in Hawaii (where it is said to be indigenous),][Nelson, Scot C. "Cassytha filiformis". Plant Disease July 2008 PD-42 Department of Plant and Environmental Protection Sciences. Cooperative extension service. University of Hawaii at Manoa. www.ctahr.hawaii.edu/oc/freepubs/pdf/PD-42.pdf] the Australasian realm
The Australasian realm is a biogeographic realm that is coincident with, but not (by some definitions) the same as, the geographical region of Australasia. The realm includes Australia, the island of New Guinea (comprising Papua New Guinea and ...
, northern South America, Central America, southern Florida, Japan, and South Africa.[Arnold T.H., de Wet B.C. (Eds), Plants of Southern Africa: Names & Distribution, MEMOIRS OF THE BOTANICAL SURVEY OF SOUTH AFRICA No. 62, Pub.National Botanical Institute, South Africa.1993 ] It also appears to have been transported to many major islands, and now is effectively pantropical
A pantropical ("all tropics") distribution is one which covers Tropics, tropical regions of both hemispheres. Examples of species include caecilians, modern sirenians and the plant genera ''Acacia'' and ''Bacopa''.
''Neotropical'' is a zoogeogra ...
.
Botanical details
The genus is cited as ''Cassytha'' L., ''Sp. Pl.'' 35 (1753), which means that Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...
formally described it in 1753 in his monumental work, ''Species Plantarum
' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genera. It is the first work to consistently apply binomial names and was the ...
''. Otto Stapf updated the work in ''Flora Capensis'' in 1912.
''Cassytha'' is unusual among Lauraceae in at least two respects: they are scandent
A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners themselv ...
herbaceous plant
Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials.
Definitions of "herb" and "herbaceous"
The fourth edition of t ...
s, and they are obligate parasite
An obligate parasite or holoparasite is a parasitic organism that cannot complete its life-cycle without exploiting a suitable host. If an obligate parasite cannot obtain a host it will fail to reproduce. This is opposed to a facultative parasite, ...
s. Their stems are thread-like or wiry, and like most twining species, they twine round the host clockwise as seen from the source of growth. The vines generally turn yellowish once they have established themselves on a productive host because they then reduce or stop their production of chlorophyll
Chlorophyll (also chlorophyl) 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 allow plants to a ...
. ''Cassytha'' species are stem parasites, adhering to their hosts by uniseriate 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 t ...
that generally are small and oblong. Their leaves are without stipules, alternate, simple, and easily overlooked, being minute and scale-like.
Various species of ''Cassytha'' bear flowers in raceme
A raceme ( or ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the s ...
s, spikes, or heads
A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may no ...
. Depending on the species, the flowers are sessile
Sessility, or sessile, may refer to:
* Sessility (motility), organisms which are not able to move about
* Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant
* Sessility (medicine), tumors and polyps that ...
or pedicellate
In botany, a pedicel is a stem that attaches a single flower to the inflorescence. Such inflorescences are described as ''pedicellate''.
Description
Pedicel refers to a structure connecting a single flower to its inflorescence. In the absenc ...
. The individual flowers are hermaphroditic
In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes.
Many taxonomic groups of animals (mostly invertebrates) do not have separ ...
and bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...
eolate, each being attended by a bract and two smaller bracteoles. In general, the flowers are small, so much so that in many species they are inconspicuous.
The perianth
The perianth (perigonium, perigon or perigone in monocots) is the non-reproductive part of the flower, and structure that forms an envelope surrounding the sexual organs, consisting of the calyx (sepals) and the corolla (petals) or tepals when ...
has six tepal
A tepal is one of the outer parts of a flower (collectively the perianth). The term is used when these parts cannot easily be classified as either sepals or petals. This may be because the parts of the perianth are undifferentiated (i.e. of very ...
s, the three outer tepals smaller than the inner. The 12 stamens are in four whorls. The receptacle of the fertilised fruit gradually envelops the ovary, becoming the fleshy part of the ripe fruit, which often retains the dried remnants of the perianth at its tip. In effect, the resulting fruit structure is a tiny drupe
In botany, a drupe (or stone fruit) is an indehiscent fruit in which an outer fleshy part (exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pit'', ''stone'', or '' pyrena'') of hardened endocarp with a seed (''kernel'') ...
. The endocarp
Fruit anatomy is the plant anatomy of the internal structure of fruit. Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits. Agg ...
is bony and plays an important part in the reproductive process, both in protecting the seed while the fruit is eaten and in inhibiting germination until the endocarp decays, thereby permitting long-lived soil seed bank
The soil seed bank is the natural storage of seeds, often dormant, within the soil of most ecosystems. The study of soil seed banks started in 1859 when Charles Darwin observed the emergence of seedlings using soil samples from the bottom of a lak ...
s to accumulate.[Dyer, R. Allen, "The Genera of Southern African Flowering Plants". , 1975]
List of accepted ''Cassytha'' species. - Unresolved species marked with *
Some species of the cactus
A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...
genus ''Rhipsalis
''Rhipsalis'' is a genus of epiphytic flowering plants in the cactus family, typically known as mistletoe cacti. They are found in parts of Central America, the Caribbean and northern regions of South America. They also inhabit isolated location ...
'' once were assigned to ''Cassytha'' in an error arising from the resemblance in habitus. An unfortunate consequence has been that the homonym
In linguistics, homonyms are words which are homographs (words that share the same spelling, regardless of pronunciation), or homophones (equivocal words, that share the same pronunciation, regardless of spelling), or both. Using this definition, ...
''Cassytha'' Mill.
Philip Miller FRS (1691 – 18 December 1771) was an English botanist and gardener of Scottish descent. Miller was chief gardener at the Chelsea Physic Garden for nearly 50 years from 1722, and wrote the highly popular '' The Gardeners Dict ...
(1768) is often mentioned as a synonym
A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of the genus ''Rhipsalis
''Rhipsalis'' is a genus of epiphytic flowering plants in the cactus family, typically known as mistletoe cacti. They are found in parts of Central America, the Caribbean and northern regions of South America. They also inhabit isolated location ...
'', although this perception is incorrect, since the generic name ''Cassytha'' had already been applied to a completely different genus in a different plant family.
The morphology and ecology of ''Cassytha'' are so atypical of the family Lauraceae, they have been the subject of molecular genetic research to confirm their taxonomic relationships. Though special aspects to their phylogeny certainly are under debate, their assignment to the Lauraceae generally is regarded as undoubtedly correct.[
]
Reproduction and ecology
''Cassytha'' fruits are ecologically valuable to some fruit-eating birds. The birds either regurgitate the seeds or pass them through their gut. Mammals, for example Australian macropods
Macropod may refer to:
* Macropodidae, a marsupial family which includes kangaroos, wallabies, tree-kangaroos, pademelons, and several others
* Macropodiformes
The Macropodiformes , also known as macropods, are one of the three suborders of the ...
, also transport the seeds in their gut.[ The bony endocarp that protects the seed in its passage through animal gut also prevents the seed from immediate germination even if conditions are favourable. Instead, the seeds survive on or in the ground till decay weakens the endocarp sufficiently to permit moisture to enter and germination to begin. This process is not deterministic, so some of the seeds might remain inactive in the soil seed bank for many years before they germinate at unpredictable intervals. Accordingly, once soil is infested with large numbers of seeds, eradication of the population generally requires considerable time. On germination, the seedlings behave as aggressive parasites; they twist about till they find a host, and those that fail to locate hosts soon die, typically in months.][
Seedlings and actively growing shoots are green at first. Once their haustoria are fully established on a suitable host, the plants lose most of their chlorophyll and generally become yellowish or orange, and the ''Cassytha'' plant abandons its connections with its root, which soon dies.
''Cassytha'' species are ]perennials
A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also widel ...
; although they attack practically whatever host plants they encounter, including suitable annuals. They seem to show some preference for woody perennial hosts. Consequently, they often find themselves on seasonally dormant host species. When that happens and the supplies from the host largely dry up, the stems of most species of ''Cassytha'' turn green until the host once again becomes productive. This suggests that such species are at least marginally photosynthetic
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...
, but do not invest resources unnecessarily when photosynthesis is not required. ''Cassytha'' species do produce some of their own nutrients while green, so their chlorophyll production is both actual and functional.
Technically, ''Cassytha'' could be regarded as hemiparasitic
A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the ...
rather than holoparasitic
A parasitic plant is a plant that derives some or all of its nutritional requirements from another living plant. They make up about 1% of angiosperms and are found in almost every biome. All parasitic plants develop a specialized organ called the ...
, but their own autotroph
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", ...
ic contributions are plainly limited to what it takes to tide over temporary shortages. When all the hosts of a plant die, so does the parasite, so whatever the details of their biology, ''Cassytha'' species certainly are unconditionally obligately parasitic. No doubt their lack of a persistent root system dooms any ''Cassytha'' plants whose hosts supply insufficient water and mineral nutrients.
The effects of ''Cassytha'' on host plants varies. They are not very selective and they parasitise hosts from many plant families, often overwhelming a host so drastically as to kill it. Even when host plants survive, a heavy infestation commonly causes drastic reduction in vigour and reproductive capacity. Accordingly, some species of ''Cassytha'' have been examined as potential weed control agents, and others are regarded as agricultural pests in their own right.
Although ''Cassytha'' species are vigorous parasites, they are less aggressive, and correspondingly less serious agricultural pests, than ''Cuscuta'' species; ''Cuscuta'' species generally grow several times faster, produce more seed, and germinate more rapidly, though their seeds are less persistent in the soil.
Among their various ecological effects, ''Cassytha'' species act as vectors, though not exclusive vectors, for various plant diseases. They may pass various fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
, ''Agrobacterium
''Agrobacterium'' is a genus of Gram-negative bacteria established by H. J. Conn that uses horizontal gene transfer to cause tumors in plants. '' Agrobacterium tumefaciens'' is the most commonly studied species in this genus. ''Agrobacterium'' i ...
'' species, virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
es, and other pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
s to host plants, or from one host plant to another.
Classification
Due to its herbaceous and parasitic habit, distinguishing the genus from all other Lauraceae, ''Cassytha'' has historically presented a problem for classification. Most early systems of classification based on morphological characters divided the Lauraceae into two subfamilies: Cassythoideae and Lauroideae;[van der Werff H & Richter HG. 1996. Toward an improved classification of Lauraceae. ''Annals of the Missouri Botanical Garden']
83: 409-418.
/ref> however, more recent molecular data disputes this division.
Based on the ''trn''K intron, a common phylogenetic marker for classifying angiosperms, Rohwer and Rudolph (2005) created a phylogeny of the Lauraceae. They nested ''Cassytha'' within the family, more closely related to '' Caryodaphnopsis,'' and placed both as sister to the tribe Cryptocaryeae, one of the three tribes of the Lauroideae''.'' More recently, embryological evidence, specifically the development of the anther tapetum, substantiated the close relationship of the two genera, but nested them within the tribe Cryptocareae. Ultimately, the exact phylogeny of ''Cassytha'' is still in dispute; however, its non- basal placement within the Lauraceae is undoubtedly accurate.
Uses
''Cassytha'' is best known for its parasitic habit, and the various species are neither prominent as crop plants, nor as beneficial plants. Species within the genus do have minor uses in rural communities globally. For example, the fruit of various species are eaten, both by birds and by humans, and ''C. melantha'' in particular has been documented as a wild-harvested Australian indigenous food. The flesh of fruit is very sticky and chewy, and has a taste reminiscent of feijoa. In the Caribbean
The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...
region, ''C. filiformis'' is one of the plant species known as love vine, because it has a reputation as an aphrodisiac.
Plants in the genus contain low concentrations of several alkaloids that have not yet been shown to be of great value, but do have biochemical properties worthy of investigation.[Stévigny C, Block S, De Pauw-Gillet MC, de Hoffmann E, Llabrès G, Adjakidjé V, Quetin-Leclercq J. Cytotoxic aporphine alkaloids from Cassytha filiformis. Planta Med. 2002 Nov ;68(11):1042-4.] Together with the fragrant essential oils in some species, the alkaloids might be relevant to the wide application of ''Cassytha'' species in folk medicine and in traditional teas.[Watt, John Mitchell; Breyer-Brandwijk, Maria Gerdina: The Medicinal and Poisonous Plants of Southern and Eastern Africa 2nd ed Pub. E & S Livingstone 1962]
Though they are not of commercial interest as fibre crops, suitably prepared vines from some ''Cassytha'' species are of value in rural communities as a source of cord. They may be used for binding bundles of materials such as thatch, or for stringing decorative festoons.
References
Further reading
*
*
*
*
*
{{Taxonbar, from=Q311184
Lauraceae genera
Medicinal plants
Parasitic plants
Pantropical flora