|Copyright: Luis alberto (semprempe)
|Date Taken: 2012-03-20|
|Camera: Canon 550D, 18-55 Canon EFS|
|Exposure: f/7.1, 1/125 seconds|
|More Photo Info: [view]|
|Photo Version: Original Version|
|Date Submitted: 2012-03-25 15:48|
|[Note Guidelines] Photographer's Note|
From Wikipedia, the free encyclopedia
Temporal range: 82 Ma
late Cretaceous – Recent
Iris versicolor, a North American species.
Subfamilies and tribes
The Iris family or Iridaceae is a family of perennial, herbaceous and bulbous plants included in the monocot order Asparagales, taking its name from the genus Iris. Almost worldwide in distribution and one of the most important families in horticulture, it includes more than 2000 species.
3 Distribution and habitat
4.1 Evolution and phylogeny
11 External links
The Iridaceae are a prominent family, forming characteristic components of several ecoregions such as fynbos. Genera such as Crocus and Iris are significant components of the floras of parts of Eurasia, and Iris also is well-represented in North America. Gladiolus and Moraea are large genera and major constituents of the flora of sub-Saharan and Southern Africa. Sisyrinchium, with more than 140 species, is the most diversified Iridaceae genus in the Americas, where several other genera occur, many of them important in tropical horticulture.
All members of Iridaceae have petaloid, soft-textured and colorful perianths in which the three tepals of the inner whorl and the three of the outer whorl are alike in structure, shape, and often in color. This type of corolla, a feature of all families of Asparagales as well as the related order Liliales, distinguishes them from other monocots, such as grasses, palms or reeds, in which the perianth is either reduced or with the members of one or both of the whorls firm-textured and dry and often brown or green. The character that sets Iridaceae apart from other plants of the Asparagales or from the Liliales, is the male part of the flower, the androecium, which has three stamens—in most related families there are six. Another character that distinguish Iridaceae from most other members of the Asparagales is its inferior ovary, the ovary being superior in most families, with the exception of Orchidaceae and Amaryllidaceae. Apart from their flowers, the Iridaceae can usually be recognized by their characteristic leaves, sword-like and oriented edgewise to the stem and with two identical surfaces. Such leaves are termed isobilateral and unifacial. In contrast to the Irids, typical plant leaves – termed dorsiventral and bifacial – have upper and lower surfaces of different appearance and anatomy.
The Iridaceae originated in Antarctica-Australasia in the late Cretaceous, about 82 million years ago, although the family's subsequent radiation occurred elsewhere, notably in southern Africa and temperate and highland South America, at the end of the Eocene or later.
Currently, 66 genera are recognized, which are distributed among 7 subfamilies and occur in a great variety of habitats. Most species are adapted to seasonal climates that have a pronounced dry or cold period unfavourable for plant growth, during which the plants remain dormant. As a result, most species are deciduous, in that their above-ground parts (leaves and stems) die down when the bulb or corm enters dormancy. The plants thus survive periods that are unfavourable for growth by retreating underground. Evergreen species are restricted to subtropical forests or savannah, temperate grasslands and perennially moist fynbos.
In the Iridaceae the perianth is formed of two whorls of three tepals, all similar in structure, shape, and often color. Such a corolla differentiates Liliales and Asparagales from other monocots, where the number or size of the tepals are reduced, or where at least one whorl is papyraceous (firm and dry like a papyrus), and usually green or brown. The characters that differentiate Iridaceae, however, are its three stamen (related families such as Alliaceae and Amaryllidaceae have six) and an inferior ovary. Sword-like leaves parallel to the stem and with normally undifferentiated sides (termed "isobilateral" and "unifacial") are another distinctive feature.
Members of Iridaceae are herbs or, in a few cases, shrubs with woody caudex. They are almost all perennial (three Sisyrinchium species are annuals) that may be either evergreen or seasonal. The rootstock is a rhizome, bulb, or corm. The leaves are found both at the base and on the stem, usually alternate, with the blade oriented parallel to the stem and thus sheathing it at the base. This results in the characteristic fan-like arrangement found in genera like Iris. This type of leaf lacks distinct upper and lower leaf surfaces. In many South African species the leaf has a thickened midrib and often variously thickened or winged margins that may also be crisped. In some species the leaves are needle-like with narrow longitudinal grooves. Species of Moraea are unusual in the family in having channeled leaves with a distinct upper and lower surface.
Flowers may be either actinomorphic or zygomorphic. Almost all the parts are in threes, starting with two equal whorls of three usually large and showy petal-like tepals, distinct or fused in a tube. There are three stamens (rarely two), and their filaments are often partly to completely fused. Anthers have two pollen sacs opening toward the outside, or from their side, and usually along their length. The ovary is located below the tepals (except in Isophysis) with axile (rarely parietal) placentation in three locules. There is a single style branching into three at the top. Iridaceae do not present unisexual flowers, and all flowers have both a style and stamen. Most members other than Sisyrinchium produce nectar from nectaries at the base of the tepals, or on the gynoecium. Iridaceae species are usually pollinated by insects or birds. The flowers are collectively arranged in two different types of inflorescences. Simple or branched spikes occur in all Crocoideae. In other subfamilies the basic inflorescence unit is a type of zig-zagging cyme called rhipidium, which is enclosed in enlarged, opposed, bracts called spathes.
The fruit is a dry capsule, usually splitting along three sides spontaneously at maturity. It is very variable in shape and texture, from firm to cartilaginous, occasionally woody. In most genera they are tetrahedral or variously angled and without obvious adaptations for dispersal. Seeds are also varied in shape. Winged seeds adapted to wind dispersal characterize Gladiolus and Tritoniopsis and also occur in some species of Hesperantha. Globular seeds with shiny coats that are relatively long-lived occur in several genera of Crocoideae. Chasmanthe aethiopica has fleshy seeds adapted to dispersal by birds and several other species that grow in more wooded places – like Chasmanthe and some freesias – have reddish or black seeds that mimic fleshy seeds. They have a hard endosperm, with reserves of hemicellulose, oil, and protein, and a small embryo.
Distribution and habitat
Members of the Iridaceae are nearly worldwide in distribution, but remain rare in tropical lowlands and at high latitudes. The family is best represented in Southern Africa, especially the winter-rainfall region in the southwest. Other centers of diversity are temperate South and Central America (with several small genera) and the Mediterranean region (Iris and Crocus). About 2000 species are distributed among some 65 genera are recognized worldwide, just over half of them from Southern Africa, where 38 genera are known. In the Cape Floral Region alone, 707 species and 27 genera are recorded.
The family prefers open, seasonal habitats. In Africa, the montane grasslands of eastern South Africa, Swaziland and Lesotho, and the Succulent Karoo and fynbos of the Northern and Western Cape have the most species. Fewer species occur in savannas or the semi-arid central karoo, and very few in forests. The species grows in a variety of soils, derived from basalt, clay, dolerite, granite, limestone and sandstone, as well as rarer rocks like serpentine. Most species favor loamy soils, often among rocks where drainage is good, but some grow in marshes and others in pure sand. Species grow from just above the high tide mark to over 3,000 metres (9,843 ft) above sea level.
Aristea africana, a member of subfamily Aristeoideae
Tigridia pavonia, an ornamental Iridaceae from Mexico
Moraea viscaria, an African species. Diversity in color and shape of the flowers in Iridaceae is a consequence of their adaptation to different species of pollinators.
A detailed image of the flower of Sisyrinchium bellum; note that in this species both whorls of tepals are alike.
Neomarica northiana is a species that shows many differences in color and shape between both whorls of tepals.
Watsonia pyramidata, note the tubulous corola
Gladiolus illyricus, a European species which shows zygomorphic flowers
Inflorescence of Ixia dubia
A cultivated variety of Crocus
Sparaxis tricolor is cultivated worldwide as an ornamental plant.
Dietes bicolor, a South African species
Moraea sisyrinchium, an iris from Makhtesh Gadol, Negev, Israel.
The family name is based on the genus Iris, the largest and best known genus in Europe. Iris dates from 1753, when it was named by Swedish botanist Carl Linnaeus. Its name derives from the Greek goddess, Iris, who carried messages from Olympus to earth along a rainbow, whose colors were seen by Linnaeus in the multi-hued petals of many of the species. The family name is attributed to Antoine Laurent de Jussieu's 1789 Genera Plantarum, secundum ordines naturales disposita juxta methodum in Horto Regio Parisiensi exaratam, and is a conserved name, so that even if an earlier name were to be discovered for the family, Iridaceae would remain valid.
The family has been accepted in all major classification systems of the 20th century. The Cronquist system treated it as part of the order Liliales of the subclass Liliidae, the Takhtajan system placed it in an order Iridales, together with Isophysidaceae and Geosiridaceae treated as single-genus families, and the Thorne system treated it as part of the order Orchidales in its own suborder, Iridineae. The Angiosperm Phylogeny Group in 1998 and 2003 (APG and APG II, respectively) system of flowering plant classification organizes flowering plants into a "selected number of monophyletic suprafamilial groups" and placed Iridaceae in the order Asparagales, which was part of a clade called "Non Commelinoid Monocots".
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