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''Arum'' is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
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 t ...
s in the family Araceae,
native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...
to Europe, northern Africa, and western and central Asia, with the highest species diversity in the Mediterranean region.Kew World Checklist of Selected Plant Families
/ref> Frequently called arum lilies, they are not closely related to the true lilies '' Lilium''. Plants in closely related ''
Zantedeschia ''Zantedeschia'' is a genus of eight species of herbaceous, perennial, flowering plants in the family Araceae, native to southern Africa from South Africa north to Malawi. The genus has been introduced on all continents except Antarctica. ...
'' are also called "arum lilies". They are rhizomatous,
herbaceous 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 o ...
perennial plant 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 wide ...
s growing to 20–60 cm tall, with sagittate (arrowhead-shaped)
leaves A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, st ...
10–55 cm long. The
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...
s are produced in a spadix, surrounded by a 10–40 cm long, distinctively coloured
spathe 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 ...
, which may be white, yellow, brown, or purple. Some species are scented, others not. The
fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...
is a cluster of bright orange or red
berries A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit, although many pips or seeds may be present. Common examples are strawberries, ras ...
. All parts of the plants, including the berries, are poisonous, containing
calcium oxalate Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydrate ...
as
raphides Raphides (pronounced /ˈræfɪˌdiz/, singular raphide /ˈreɪfʌɪd/ or raphis) are needle-shaped crystals of calcium oxalate monohydrate ( prismatic monoclinic crystals) or calcium carbonate as aragonite ( dipyramidal orthorhombic crystals), ...
. In spite of this, the plant has a history of culinary use among Arab peasants in Palestine who practised leaching the toxins from the plant before the leaves were consumed. The genus name is the Latinized form of the Greek name for these plants, ''aron''.


Inflorescence and pollination

The
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...
s are borne on a poker-shaped
inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are forme ...
called a spadix, which is partially enclosed in a
spathe 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 ...
or leaf-like hood of varying colour. The flowers are hidden from sight, clustered at the base of the spadix with a ring of female flowers at the bottom and a ring of male flowers above them. Above the male flowers is a ring of hairs forming an insect trap. The insects are trapped beneath the ring of hairs and are dusted with
pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametop ...
by the male flowers before escaping and carrying the pollen to the spadices of other plants, where they pollinate the female flowers. Once the plant is pollinated, the small hairs wither away and the trapped insects are released. After the inflorescence opens, the spadix heats up well above ambient temperature, due to a phenomenon called thermogenesis. This is caused by the rapid consumption of starch in cyanide insensitive respiration, which is biochemically different from the respiration normally found in plants. The heat is used to vaporize odour components, which in species with short "flower-stalks" cause a faecal smell. This in turn attracts the small flies and gnats that are to be trapped within the inflorescence. As the time required for successful pollination to occur can be several days, many of the small insects nevertheless die within the flower due to their short lifespan. Therefore, dead insects are frequently found within the inflorescence, when opened, sometimes leading the finder to believe it is a carnivorous plant – but that is not the case. No digestive enzymes or similar components are present; and in fact, once pollinated, the entire inflorescence starts withering except the central part, from which the berries later emerge. pp. 35-40 Pollination-wise, the species of Arum can be split into two (or three) distinct groups. The "cryptic" species have the inflorescence on a relatively short stalk, and the odour released during the thermogenesis is recognizable to the human nose as distinctively faecal. These species are visited by insects with some relation to dung, such as owl-midges ( Psychodidae) or fungus-gnats ( Sciara). In northern Europe, only the cryptic-flowered species are found. The other main group are called "flag" species, due to the inflorescence being on a long stalk. These species also exhibit thermogenesis, but if an odour is released it is not recognizable to the human nose, and it is debated if pollinators are attracted by a non-recognizable smell, the thermogenesis itself or visual attraction. Finally the closely related ''A. idaeum'' and ''A. creticum'' does not seem to fit any of the two groups. ''A. creticum'' appears to be of the "flag" group but, as the only species, emits a pleasing lemony smell. The apparently "cryptic" ''A. idaeum'' does not emit a recognizable smell.


Species

Formerly placed here: * ''
Arisaema triphyllum ''Arisaema triphyllum'', the jack-in-the-pulpit, bog onion, brown dragon or Indian turnip, is a herbaceous perennial plant growing from a corm. It is a highly variable species typically growing in height with three-part leaves and flowers cont ...
'' (syn. ''Arum triphyllum'') * ''
Dracunculus vulgaris ''Dracunculus vulgaris'' is a species of aroid flowering plant in the genus '' Dracunculus'' and the arum family Araceae. Common names include the common dracunculus, dragon lily, dragon arum, black arum and vampire lily. In Greece, part of its n ...
'' (syn. ''Arum dracunculus'') * '' Sauromatum venosum'' (syn. ''Arum cornutum'')


See also

* List of plants known as lily


References

{{Taxonbar, from=Q161121 Araceae genera Flora of Kurdistan Taxa named by Carl Linnaeus