Commelinaceae
Encyclopedia
Commelinaceae is a family
of flowering plants. In less formal contexts, the group is referred to as the dayflower family or spiderwort family. It is one of five families in the order
Commelinales
and by far the largest of these with an estimated 650 species in 40 genera. Well known genera include Commelina
(dayflowers) and Tradescantia
(spiderworts). The family is diverse in both the Old World tropics
and the New World tropics, with some genera present in both. The variation in morphology
, especially that of the flower
and inflorescence
, is considered to be exceptionally high amongst the angiosperms.
The family has always been recognized by most taxonomists. The APG II system
of 2003 (unchanged from the APG system
of 1998), also recognizes this family, and assigns it to the order Commelinales
in the clade commelinids
in the monocots. The family counts several hundred species of herbaceous plants. Many are cultivated as ornamentals. The stems of these plants are generally well-developed, and often swollen at the nodes. Flowers are often short-lived, lasting for a day or less.
The flowers of Commelinaceae are ephemeral, lack nectar, and offer only pollen as a reward to their pollinators. Most species are bisexual, meaning each flower contains male and female organs, or andromonoecious, meaning that bisexual and male flowers occur on the same plant. Floral dimorphism
may be accompanied by variable pedicel
length, filament length and/or curvature, or stamen
number and/or position. Species tend to have specific flowering seasons, though local environmental factors tend to effect exact timing, sometimes considerably. Species tend to flower at a specific time of day as well, with these periods being well defined enough to presumably isolate different species reproductively. Furthermore, some species exhibit differential opening times for male and biseuxal flowers. Commelinaceae flowers tend to deceive pollinators by appearing to offer a larger reward than is actually present. This is accomplished with various adaptations such as yellow hairs or broad anther connectives that mimic pollen, or staminode
s that lack pollen but appear like fertile stamens.
, but a smaller number of species are annuals
. They are always terrestrial
except for plants in the genus Cochliostema
, which are epiphyte
s. Plants typically have an erect or scrambling but ascending habit, often spreading by rooting at the nodes or by stolon
s. Some have rhizome
s, and the genera Streptolirion
, Aetheolirion, and some species of Spatholirion
are climbers. The roots are either fibrous or form tuber
s.
Leaves form sheaths at their bases that surround the stem, much like the leaves of grasses, except that the sheaths are closed and do not have a ligule
. The leaves alternate up the stem and may be two-ranked or spirally arranged. The leaf blades are simple and entire (that is, they lack any teeth or lobes), they sometimes narrow at the base, and they are often succulent. The way in which the leaves typically unfurl from bud is a distinctive feature of the family: it is termed involute, and means that the margins at the leaf base are rolled in when they first emerge. However, some groups are supervolute or convolute.
The inflorescence
s occur either as a terminal shoot at the top of the plant, or as terminal and axillary shoots arising from lower nodes, or rarely as only axillary shoots that pierce through the leaf sheath such as in Coleotrype
and Amischotolype. The inflorescence is classed as a thyrse, and each subunit is made up of cincinni; this basically means that flowers are grouped in scorpion's tail-like clusters along a central axis, although this basic ground plan can become highly modified or reduced. Inflorescences or their subunit are sometimes enclosed in a leaf-like bract
often called a spathe.
Flowers can have either one or many planes of symmetry; that is either zygomorphic or actinomorphic. They remain open for only a few hours after opening, after which they deliquesce. The flowers are usually all bisexual (monoecious), but some species have both male and bisexual flowers (andromonoecious), the single species Callisia repens has bisexual and female flowers (gynomonoecious), and some have bisexual, male, and female flowers (polygamomonoecious
). nectaries are not found in any species within the family. There are always three sepal
s, although they may be equal or unequal, unfused or basally fused, petal-like or green. Likewise there are always three petals, but these may be equal or in two forms, free or basally fused, white or coloured. The petals are sometimes clawed, meaning they narrow to stalk at the base where they attach to the rest of the flower. There are almost always six stamens in two whorls, but these occur in a myriad of arrangements and forms. They may be all fertile and equal or unequal, but in many genera two to four are staminodes (i.e. infertile, non-pollen producing stamens). Staminodes can alternate with the fertile stamens or they can all occur in the upper or lower hemisphere of the flower. The stalks of the stamens are bearded in many genera, although in some of these only some are bearded while others are hairless. Sometimes one to three stamens are absent altogether. Pollen is usually released from slits that open on the sides of the anthers from top to bottom, but some species have pores that open at the tips.
gene rbcL
All clades shown have 80% bootstrap support
or better.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of flowering plants. In less formal contexts, the group is referred to as the dayflower family or spiderwort family. It is one of five families in the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Commelinales
Commelinales
Commelinales is the botanical name of an order of flowering plants. It comprises five families: Commelinaceae, Haemodoraceae, Hanguanaceae, Philydraceae, and Pontederiaceae. All the families combined contain over 800 species in about 70 genera; the majority of species are in the Commelinaceae...
and by far the largest of these with an estimated 650 species in 40 genera. Well known genera include Commelina
Commelina
Commelina is a genus of approximately 170 species commonly called dayflowers due to the short lives of their flowers. They are less often known as widow's tears. It is by far the largest genus of its family, Commelinaceae...
(dayflowers) and Tradescantia
Tradescantia
Tradescantia , the Spiderworts, is a genus of an estimated 71 species of perennial plants in the family Commelinaceae, native to the New World from southern Canada south to northern Argentina. They are weakly upright to scrambling plants, growing to 30–60 cm tall, and are commonly found...
(spiderworts). The family is diverse in both the Old World tropics
Paleotropical Kingdom
The Paleotropical Kingdom is a floristic kingdom comprising tropical areas of Africa, Asia and Oceania , as proposed by Ronald Good and Armen Takhtajan. Its flora is characterized by about 40 endemic plant families, e.g. Nepenthaceae, Musaceae, Pandanaceae, Flagellariaceae...
and the New World tropics, with some genera present in both. The variation in morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, especially that of the flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
and inflorescence
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. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
, is considered to be exceptionally high amongst the angiosperms.
The family has always been recognized by most taxonomists. The APG II system
APG II system
The APG II system of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Group. It was a revision of the first APG system, published in 1998, and was superseded in 2009...
of 2003 (unchanged from the APG system
APG system
The APG system of plant classification is the first, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in 1998 by the Angiosperm Phylogeny Group. It was superseded in 2003 by a revision, the APG II system, and then in 2009 by a further...
of 1998), also recognizes this family, and assigns it to the order Commelinales
Commelinales
Commelinales is the botanical name of an order of flowering plants. It comprises five families: Commelinaceae, Haemodoraceae, Hanguanaceae, Philydraceae, and Pontederiaceae. All the families combined contain over 800 species in about 70 genera; the majority of species are in the Commelinaceae...
in the clade commelinids
Commelinids
In plant taxonomy, commelinids is a name used by the APG III system for a clade within the monocots, which in its turn is a clade within the angiosperms. The commelinids are the only clade that the APG has informally named within the monocots...
in the monocots. The family counts several hundred species of herbaceous plants. Many are cultivated as ornamentals. The stems of these plants are generally well-developed, and often swollen at the nodes. Flowers are often short-lived, lasting for a day or less.
The flowers of Commelinaceae are ephemeral, lack nectar, and offer only pollen as a reward to their pollinators. Most species are bisexual, meaning each flower contains male and female organs, or andromonoecious, meaning that bisexual and male flowers occur on the same plant. Floral dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
may be accompanied by variable pedicel
Pedicel (botany)
A pedicel is a stem that attaches single flowers to the main stem of the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower....
length, filament length and/or curvature, or stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
number and/or position. Species tend to have specific flowering seasons, though local environmental factors tend to effect exact timing, sometimes considerably. Species tend to flower at a specific time of day as well, with these periods being well defined enough to presumably isolate different species reproductively. Furthermore, some species exhibit differential opening times for male and biseuxal flowers. Commelinaceae flowers tend to deceive pollinators by appearing to offer a larger reward than is actually present. This is accomplished with various adaptations such as yellow hairs or broad anther connectives that mimic pollen, or staminode
Staminode
In botany, a staminode is an often rudimentary, sterile or abortive stamen. This means that it does not produce pollen. Staminodes are frequently inconspicuous and stamen-like, usually occurring at the inner whorl of the flower, but are also sometimes long enough to protrude from the...
s that lack pollen but appear like fertile stamens.
Description
Plants in the Commelinaceae are usually perennialsPerennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
, but a smaller number of species are annuals
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
. They are always terrestrial
Terrestrial plant
A terrestrial plant is one that grows on land. Other types of plants are aquatic , epiphytic , lithophytes and aerial ....
except for plants in the genus Cochliostema
Cochliostema
Cochliostema is a genus of plants with two species in the family Commelinaceae . The genus occurs from southern Nicaragua to southern Ecuador.-Systematics:...
, which are epiphyte
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
s. Plants typically have an erect or scrambling but ascending habit, often spreading by rooting at the nodes or by stolon
Stolon
In biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.-In botany:...
s. Some have rhizome
Rhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
s, and the genera Streptolirion
Streptolirion
Streptolirion is a genus of climbing monocotyledonous flowering plants in the dayflower family. It consists of a single species, namely Streptolirion volubile. It has a broad distribution in Asia, from China's western Hubei Province as well as Korea and Japan in the northeast, south to Vietnam and...
, Aetheolirion, and some species of Spatholirion
Spatholirion
Spatholirion is a genus of climbing or rosette monocotyledonous flowering plants in the dayflower family. It is distributed from China in the north, south to Thailand, Vietnam, and northern Peninsular Malaysia. It has four to eight seeds per carpel, unlike the closely related Streptolirion, which...
are climbers. The roots are either fibrous or form tuber
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...
s.
Leaves form sheaths at their bases that surround the stem, much like the leaves of grasses, except that the sheaths are closed and do not have a ligule
Ligule
A ligule — is a thin outgrowth at the junction of leaf and leafstalk of many grasses and sedges or a strap-shaped corolla, such as that of a ray floret in plants in the daisy family....
. The leaves alternate up the stem and may be two-ranked or spirally arranged. The leaf blades are simple and entire (that is, they lack any teeth or lobes), they sometimes narrow at the base, and they are often succulent. The way in which the leaves typically unfurl from bud is a distinctive feature of the family: it is termed involute, and means that the margins at the leaf base are rolled in when they first emerge. However, some groups are supervolute or convolute.
The inflorescence
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. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
s occur either as a terminal shoot at the top of the plant, or as terminal and axillary shoots arising from lower nodes, or rarely as only axillary shoots that pierce through the leaf sheath such as in Coleotrype
Coleotrype
Coleotrype is a genus of perennial monocotyledonous flowering plants in the dayflower family. It is found in Africa and Madagascar and consists of about nine species...
and Amischotolype. The inflorescence is classed as a thyrse, and each subunit is made up of cincinni; this basically means that flowers are grouped in scorpion's tail-like clusters along a central axis, although this basic ground plan can become highly modified or reduced. Inflorescences or their subunit are sometimes enclosed in a leaf-like bract
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 often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
often called a spathe.
Flowers can have either one or many planes of symmetry; that is either zygomorphic or actinomorphic. They remain open for only a few hours after opening, after which they deliquesce. The flowers are usually all bisexual (monoecious), but some species have both male and bisexual flowers (andromonoecious), the single species Callisia repens has bisexual and female flowers (gynomonoecious), and some have bisexual, male, and female flowers (polygamomonoecious
Polygamomonoecious
The term polygamomonoecious has two meanings in botany:*an individual plant with male, female, and perfect flowers on the same plant, called trimonoecious or polygamomonoecious plants;...
). nectaries are not found in any species within the family. There are always three sepal
Sepal
A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...
s, although they may be equal or unequal, unfused or basally fused, petal-like or green. Likewise there are always three petals, but these may be equal or in two forms, free or basally fused, white or coloured. The petals are sometimes clawed, meaning they narrow to stalk at the base where they attach to the rest of the flower. There are almost always six stamens in two whorls, but these occur in a myriad of arrangements and forms. They may be all fertile and equal or unequal, but in many genera two to four are staminodes (i.e. infertile, non-pollen producing stamens). Staminodes can alternate with the fertile stamens or they can all occur in the upper or lower hemisphere of the flower. The stalks of the stamens are bearded in many genera, although in some of these only some are bearded while others are hairless. Sometimes one to three stamens are absent altogether. Pollen is usually released from slits that open on the sides of the anthers from top to bottom, but some species have pores that open at the tips.
Phylogeny
The following is a phylogeny, or evolutionary tree, of most of the genera in Commelinaceae based on DNA sequences from the plastidPlastid
Plastids are major organelles found in the cells of plants and algae. Plastids are the site of manufacture and storage of important chemical compounds used by the cell...
gene rbcL
All clades shown have 80% bootstrap support
Bootstrapping (statistics)
In statistics, bootstrapping is a computer-based method for assigning measures of accuracy to sample estimates . This technique allows estimation of the sample distribution of almost any statistic using only very simple methods...
or better.
External links
- Commelinaceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants: descriptions, illustrations, identification, information retrieval. Version: 9 March 2006. http://delta-intkey.com.
- NCBI Taxonomy Browser
- links at CSDL