Monocots
   HOME

TheInfoList



OR:

Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are
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 whose
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s contain only one
embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...
nic leaf, or
cotyledon A cotyledon ( ; ; "a cavity, small cup, any cup-shaped hollow", gen. (), ) is a "seed leaf" – a significant part of the embryo within the seed of a plant – and is formally defined as "the embryonic leaf in seed-bearing plants, one or mor ...
. A monocot
taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
has been in use for several decades, but with various ranks and under several different names. The
APG IV system The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was publish ...
recognises its
monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...
but does not assign it to a taxonomic rank, and instead uses the term "monocots" to refer to the group. Monocotyledons are contrasted with the dicotyledons, which have two cotyledons. Unlike the monocots however, the dicots are not
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
and the two cotyledons are instead the ancestral characteristic of all flowering plants. Botanists now classify dicots into the
eudicots The eudicots or eudicotyledons are flowering plants that have two seed leaves (cotyledons) upon germination. The term derives from ''dicotyledon'' (etymologically, ''eu'' = true; ''di'' = two; ''cotyledon'' = seed leaf). Historically, authors h ...
("true dicots") and several basal lineages from which the monocots emerged. The monocots are extremely important economically, culturally, and ecologically, and make up a majority of plant biomass used in agriculture. Common crops such as dates,
onion An onion (''Allium cepa'' , from Latin ), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus '' Allium''. The shallot is a botanical variety of the onion which was classifie ...
s,
garlic Garlic (''Allium sativum'') is a species of bulbous flowering plants in the genus '' Allium''. Its close relatives include the onion, shallot, leek, chives, Welsh onion, and Chinese onion. Garlic is native to central and south Asia, str ...
,
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 ...
,
wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...
,
maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...
, and
sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...
are all monocots. The grasses alone cover over 40% of Earth's land area and contribute a significant portion of the human diet. Other monocots, like
orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Eart ...
s,
tulip Tulips are spring-blooming perennial herbaceous bulbiferous geophytes in the ''Tulipa'' genus. Their flowers are usually large, showy, and brightly coloured, generally red, orange, pink, yellow, or white. They often have a different colour ...
s, daffodils, and lilies are common
houseplant A houseplant, also known as a pot plant, potted plant, or indoor plant, is an ornamental plant cultivated indoors. for aesthetic or practical purposes. These plants are commonly found in House, homes, Office, offices, and various indoor spaces, w ...
s and have been the subjects of several celebrations, holidays, and artworks for thousands of years.


Description

The monocots have, as the name implies, a single (mono-)
cotyledon A cotyledon ( ; ; "a cavity, small cup, any cup-shaped hollow", gen. (), ) is a "seed leaf" – a significant part of the embryo within the seed of a plant – and is formally defined as "the embryonic leaf in seed-bearing plants, one or mor ...
, or embryonic leaf, in their
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s. Historically, this feature was used to contrast the monocots with the
dicotyledon The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, ...
s or dicots which typically have two cotyledons; however, modern research has shown that the dicots are
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
. From a diagnostic point of view the number of cotyledons is neither a particularly useful characteristic (as they are only present for a very short period in a plant's life), nor is it completely reliable. The single cotyledon is only one of a number of modifications of the
body plan A body plan, (), or ground plan is a set of morphology (biology), morphological phenotypic trait, features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many. This term, usually app ...
of the ancestral monocotyledons, whose adaptive advantages are poorly understood, but may have been related to adaption to aquatic habitats, prior to
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...
to terrestrial habitats. Nevertheless, monocots are sufficiently distinctive that there has rarely been disagreement as to membership of this group, despite considerable diversity in terms of external morphology. With over 70,000 species, monocots are extremely evolutionarily successful and occupy a diverse set of niches:
Perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...
geophytes including
orchids Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Earth ...
(
Asparagales Asparagales (asparagoid lilies) are a diverse order of flowering plants in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 genera, and about 36,00 ...
); tulips and lilies (
Liliales Liliales is an order (biology), order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web List of systems of plant classification, system, within the lilioid monocots. This order of necessity includ ...
); rosette and succulent
epiphytes 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 ...
(Asparagales); mycoheterotrophs (Liliales, Dioscoreales, Pandanales), all in the
lilioid monocots Lilioid monocots (lilioids, liliid monocots, petaloid monocots, petaloid lilioid monocots) is an informal name used for a grade (biology), grade (grouping of taxa with common characteristics) of five monocot order (biology), orders (Petrosavial ...
; major
cereal A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize ( Corn). Edible grains from other plant families, ...
grains A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and le ...
(
maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...
,
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 ...
,
barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...
, rye,
oats The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural). Oats appear to have been domesticated as a secondary crop, as their seed ...
,
millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most millets belong to the tribe Paniceae. Millets are important crops in the Semi-arid climate, ...
,
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 ...
and
wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...
) in the grass family; and forage grasses (
Poales The Poales are a large order (biology), order of flowering plants in the monocotyledons, and includes families of plants such as the Poaceae, grasses, bromeliads, Juncaceae, rushes and Cyperaceae, sedges. 14 plant families are currently recogniz ...
) as well as woody tree-like palm trees ( Arecales),
bamboo Bamboos are a diverse group of mostly evergreen perennial plant, perennial flowering plants making up the subfamily (biology), subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family, in th ...
, reeds and bromeliads (Poales),
bananas A banana is an elongated, edible fruit – berry (botany), botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus ''Musa (genus), Musa''. In some countries, cooking bananas are called pla ...
and
ginger Ginger (''Zingiber officinale'') is a flowering plant whose rhizome, ginger root or ginger, is widely used as a spice and a folk medicine. It is an herbaceous perennial that grows annual pseudostems (false stems made of the rolled bases of l ...
(
Zingiberales The Zingiberales are flowering plants forming one of four orders in the commelinids clade of monocots, together with its sister order, Commelinales. The order includes 68 genera and 2,600 species. Zingiberales are a unique though morpholog ...
) in the commelinid monocots, as well as floating or submerged aquatic plants such as
seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...
( Alismatales) are all monocots.


Vegetative


Organisation, growth and life forms

The most important distinction is their growth pattern, lacking a lateral meristem (
cambium A cambium (: cambiums or cambia), in plants, is a tissue layer that provides partially undifferentiated cells for plant growth. It is found in the area between xylem and phloem. A cambium can also be defined as a cellular plant tissue from whic ...
) that allows for continual growth in diameter with height ( secondary growth), and therefore this characteristic is a basic limitation in shoot construction. Although largely herbaceous, some arboraceous monocots reach great height, length and mass. The latter include agaves, palms, pandans, and bamboos. This creates challenges in water transport that monocots deal with in various ways. Some, such as species of ''
Yucca ''Yucca'' ( , YUCK-uh) is both the scientific name and common name for a genus native to North America from Panama to southern Canada. It contains 50 accepted species. In addition to yucca, they are also known as Adam's needle or Spanish-bayon ...
'', develop anomalous secondary growth, while palm trees utilise an anomalous primary growth form described as establishment growth (''see'' Vascular system). The axis undergoes primary thickening, that progresses from internode to internode, resulting in a typical inverted conical shape of the basal primary axis (''see'' Tillich, Figure 1). The limited conductivity also contributes to limited branching of the stems. Despite these limitations a wide variety of adaptive growth forms has resulted (Tillich, Figure 2) from
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 ...
orchids Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Earth ...
(Asparagales) and bromeliads (Poales) to submarine Alismatales (including the reduced Lemnoideae) and mycotrophic Burmanniaceae (Dioscreales) and Triuridaceae (Pandanales). Other forms of adaptation include the climbing vines of
Araceae The Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe (or leaf-like bract). Also ...
(Alismatales) which use negative phototropism ( skototropism) to locate host trees (''i.e.'' the darkest area), while some palms such as '' Calamus manan'' ( Arecales) produce the longest shoots in the plant kingdom, up to 185 m long. Other monocots, particularly
Poales The Poales are a large order (biology), order of flowering plants in the monocotyledons, and includes families of plants such as the Poaceae, grasses, bromeliads, Juncaceae, rushes and Cyperaceae, sedges. 14 plant families are currently recogniz ...
, have adopted a therophyte life form.


Leaves

The cotyledon, the primordial Angiosperm
leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...
consists of a proximal leaf base or hypophyll and a distal hyperphyll. In monocots the hypophyll tends to be the dominant part in contrast to other angiosperms. From these, considerable diversity arises. Mature monocot leaves are generally narrow and linear, forming a sheathing around the stem at its base, although there are many exceptions. Leaf venation is of the striate type, mainly arcuate-striate or longitudinally striate (parallel), less often palmate-striate or pinnate-striate with the leaf veins emerging at the leaf base and then running together at the apices. There is usually only one leaf per node because the leaf base encompasses more than half the circumference. The evolution of this monocot characteristic has been attributed to developmental differences in early zonal differentiation rather than meristem activity (leaf base theory).


Roots and underground organs

The lack of cambium in the primary
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 ...
limits its ability to grow sufficiently to maintain the plant. This necessitates early development of roots derived from the shoot (adventitious roots). In addition to roots, monocots develop runners and
rhizomes In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow hori ...
, which are creeping shoots. Runners serve vegetative propagation, have elongated internodes, run on or just below the surface of the soil and in most case bear scale leaves. Rhizomes frequently have an additional storage function and rhizome producing plants are considered geophytes (Tillich, Figure 11). Other geophytes develop bulbs, a short axial body bearing leaves whose bases store food. Additional outer non-storage leaves may form a protective function (Tillich, Figure 12). Other storage organs may be
tubers Tubers are a type of enlarged structure that plants use as storage organs for nutrients, derived from stems or roots. Tubers help plants perennate (survive winter or dry months), provide energy and nutrients, and are a means of asexual reprod ...
or corms, swollen axes. Tubers may form at the end of underground runners and persist. Corms are short lived vertical shoots with terminal inflorescences and shrivel once flowering has occurred. However, intermediate forms may occur such as in '' Crocosmia'' (Asparagales). Some monocots may also produce shoots that grow directly down into the soil, these are geophilous shoots (Tillich, Figure 11) that help overcome the limited trunk stability of large woody monocots.


Reproductive


Flowers

In nearly all cases the perigone consists of two alternating trimerous whorls of
tepals 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 ve ...
, being homochlamydeous, without differentiation between calyx and corolla. In zoophilous (pollinated by animals) taxa, both whorls are corolline (petal-like). Anthesis (the period of flower opening) is usually fugacious (short lived). Some of the more persistent perigones demonstrate thermonastic opening and closing (responsive to changes in temperature). About two thirds of monocots are zoophilous, predominantly by
insects Insects (from Latin ') are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed ...
. These plants need to advertise to pollinators and do so by way of phaneranthous (showy) flowers. Such optical signalling is usually a function of the tepal whorls but may also be provided by semaphylls (other structures such as filaments, staminodes or stylodia which have become modified to attract pollinators). However, some monocot plants may have aphananthous (inconspicuous) flowers and still be pollinated by animals. In these the plants rely either on chemical attraction or other structures such as coloured bracts fulfill the role of optical attraction. In some phaneranthous plants such structures may reinforce floral structures. The production of fragrances for olfactory signalling are common in monocots. The perigone also functions as a landing platform for pollinating insects.


Fruit and seed

The
embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...
consists of a single cotyledon, usually with two vascular bundles.


Comparison with dicots

The traditionally listed differences between monocots and dicots are as follows. This is a broad sketch only, not invariably applicable, as there are a number of exceptions. The differences indicated are more true for monocots versus
eudicots The eudicots or eudicotyledons are flowering plants that have two seed leaves (cotyledons) upon germination. The term derives from ''dicotyledon'' (etymologically, ''eu'' = true; ''di'' = two; ''cotyledon'' = seed leaf). Historically, authors h ...
. A number of these differences are not unique to the monocots, and, while still useful, no one single feature will infallibly identify a plant as a monocot. For example, trimerous flowers and monosulcate pollen are also found in magnoliids, and exclusively adventitious roots are found in some of the
Piperaceae The Piperaceae (), also known as the pepper family, are a large family (biology), family of flowering plants. The group contains roughly 3,600 currently accepted species in five genera. The vast majority of species can be found within the two mai ...
. Similarly, at least one of these traits, parallel leaf veins, is far from universal among the monocots. Broad leaves and reticulate leaf veins, features typical of dicots, are found in a wide variety of monocot families: for example, ''
Trillium ''Trillium'' (trillium, wakerobin, toadshade, tri flower, birthroot, birthwort, and sometimes "wood lily") is a genus of about fifty flowering plant species in the family Melanthiaceae. ''Trillium'' species are native to temperate regions of No ...
'', '' Smilax'' (greenbriar), '' Pogonia'' (an orchid), and the Dioscoreales (yams). '' Potamogeton'' and '' Paris quadrifolia'' (herb-paris) are examples of monocots with tetramerous flowers. Other plants exhibit a mixture of characteristics.
Nymphaeaceae Nymphaeaceae () is a family of flowering plants, commonly called water lilies. They live as rhizomatous aquatic herbs in temperate climate, temperate and tropical climates around the world. The family contains five genera with about 70 know ...
(water lilies) have reticulate veins, a single cotyledon, adventitious roots, and a monocot-like vascular bundle. These examples reflect their shared ancestry. Nevertheless, this list of traits is generally valid, especially when contrasting monocots with eudicots, rather than non-monocot flowering plants in general.


Apomorphies

Monocot
apomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...
(characteristics derived during
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...
rather than inherited from an ancestral form) include
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 of ...
habit, leaves with parallel venation and sheathed base, an embryo with a single cotyledon, an atactostele, numerous adventitious roots,
sympodial In botany, sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, als ...
growth, and trimerous (3 parts per whorl) flowers that are pentacyclic (5 whorled) with 3 sepals, 3 petals, 2 whorls of 3 stamens each, and 3 carpels. In contrast, monosulcate pollen is considered an ancestral trait, probably plesiomorphic.


Synapomorphies

The distinctive features of the monocots have contributed to the relative taxonomic stability of the group. Douglas E. Soltis and others identify thirteen synapomorphies (shared characteristics that unite monophyletic groups of taxa); # Calcium oxalate raphides # Absence of vessels in leaves # Monocotyledonous
anther The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...
wall formation* # Successive microsporogenesis # Syncarpous
gynoecium Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl (botany), whorl of a flower; it consists ...
# Parietal
placentation Placentation is the formation, type and structure, or modes of arrangement of the placenta. The function of placentation is to transfer nutrients, respiratory gases, and water from maternal tissue to a growing embryo, and in some instances to re ...
# Monocotyledonous
seedling A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embry ...
# Persistent radicle # Haustorial cotyledon tip # Open cotyledon sheath # Steroidal
saponins Saponins (Latin ''sapon'', 'soap' + ''-in'', 'one of') are bitter-tasting, usually toxic plant-derived secondary metabolites. They are Organic compound, organic chemicals that become foamy when agitated in water and have high Molar mass, molecul ...
* # Fly pollination* # Diffuse vascular bundles and absence of secondary growth


Vascular system

Monocots have a distinctive arrangement of vascular tissue known as an atactostele in which the vascular tissue is scattered rather than arranged in concentric rings. Collenchyma is absent in monocot stems, roots and leaves. Many monocots are
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 of ...
and do not have the ability to increase the width of a stem ( secondary growth) via the same kind of
vascular cambium The vascular cambium is the main growth tissue in the stems and roots of many plants exhibiting secondary growth, specifically in dicots such as buttercups and oak trees, gymnosperms such as pine trees, as well as in certain other vascular ...
found in non-monocot
woody plant A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposed to Herbaceous plant, herbaceous plants that die back to t ...
s. However, some monocots do have secondary growth; because this does not arise from a single vascular cambium producing
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 ...
inwards and phloem outwards, it is termed "anomalous secondary growth". Examples of large monocots which either exhibit secondary growth, or can reach large sizes without it, are palms (
Arecaceae The Arecaceae () is a family (biology), family of perennial plant, perennial, flowering plants in the Monocotyledon, monocot order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, all commonly k ...
), screwpines ( Pandanaceae), bananas ( Musaceae), ''
Yucca ''Yucca'' ( , YUCK-uh) is both the scientific name and common name for a genus native to North America from Panama to southern Canada. It contains 50 accepted species. In addition to yucca, they are also known as Adam's needle or Spanish-bayon ...
'', ''
Aloe ''Aloe'' (; also written ''Aloë'') is a genus containing over 650 species of flowering plant, flowering succulent plant, succulent plants.WFO (2022): Aloe L. Published on the Internet;http://www.worldfloraonline.org/taxon/wfo-4000001341. Acc ...
'', '' Dracaena'', and '' Cordyline''.


Taxonomy


Early history


Pre-Linnean

Monocots were first recognized as a group in Matthias de l'Obel's ''Stirpium adversaria nova''. Searching for non-pharmacological characteristics to classify plants by, he chose on
leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...
form and venation, and observed that the majority of plants had broad leaves with net-like venation, but some had long and straight leaves with parallel veins. He did not decide on any formal name for the two groups he discovered, and his new classification scheme did not receive much appraisal and only saw moderate success within academic circles. Formal description dates from John Ray's studies of
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
structure in the 17th century. Ray, who is often considered the first botanical systematist, observed the
dichotomy A dichotomy () is a partition of a set, partition of a whole (or a set) into two parts (subsets). In other words, this couple of parts must be * jointly exhaustive: everything must belong to one part or the other, and * mutually exclusive: nothi ...
of
cotyledon A cotyledon ( ; ; "a cavity, small cup, any cup-shaped hollow", gen. (), ) is a "seed leaf" – a significant part of the embryo within the seed of a plant – and is formally defined as "the embryonic leaf in seed-bearing plants, one or mor ...
structure in his examination of seeds. He reported his findings in a paper read to the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
on 17 December 1674, entitled "A Discourse on the Seeds of Plants". Since this paper appeared a year before the publication of Malpighi's ''Anatome Plantarum'' (1675–1679), Ray has the priority. At the time, Ray did not fully realise the importance of his discovery but progressively developed this over successive publications. And since these were in Latin, "seed leaves" became ''folia seminalia'' and then ''cotyledon'', following Malpighi. Malpighi and Ray were familiar with each other's work, and Malpighi in describing the same structures had introduced the term cotyledon, which Ray adopted in his subsequent writing. In this experiment, Malpighi also showed that the cotyledons were critical to the development of the plant, proof that Ray required for his theory. In his ''Methodus plantarum nova'' Ray also developed and justified the "natural" or pre-evolutionary approach to classification, based on characteristics selected '' a posteriori'' in order to group together taxa that have the greatest number of shared characteristics. This approach, also referred to as polythetic would last till
evolutionary theory Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certai ...
enabled
Eichler Several people are named Eichler: * August W. Eichler (1839–1887), German botanist * Caroline Eichler (1808/9–1843), German inventor, first woman to be awarded a patent (for her leg prosthesis) * Eunice Eichler (1932–2017), New Zealand Salvat ...
to develop the phyletic system that superseded it in the late nineteenth century, based on an understanding of the acquisition of characteristics. He also made the crucial observation ''Ex hac seminum divisione sumum potest generalis plantarum distinctio, eaque meo judicio omnium prima et longe optima, in eas sci. quae plantula seminali sunt bifolia aut διλόβω, et quae plantula sem. adulta analoga.'' (From this division of the seeds derives a general distinction amongst plants, that in my judgement is first and by far the best, into those seed plants which are bifoliate, or bilobed, and those that are analogous to the adult), that is between monocots and dicots. He illustrated this by quoting from Malpighi and including reproductions of Malpighi's drawings of cotyledons (see figure). Initially Ray did not develop a classification of flowering plants (florifera) based on a division by the number of cotyledons, but developed his ideas over successive publications, coining the terms ''Monocotyledones'' and ''Dicotyledones'' in 1703, in the revised version of his ''Methodus'' (''Methodus plantarum emendata''), as a primary method for dividing them, ''Herbae floriferae, dividi possunt, ut diximus, in Monocotyledones & Dicotyledones'' (Flowering plants, can be divided, as we have said, into Monocotyledons & Dicotyledons).


Post Linnean

Although
Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
(1707–1778) did not utilise Ray's discovery, basing his own classification solely on floral reproductive morphology, the term was used shortly after his classification appeared (1753) by Scopoli and who is credited for its introduction. Every
taxonomist In biology, taxonomy () is the science, scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxon, taxa (si ...
since then, starting with De Jussieu and De Candolle, has used Ray's distinction as a major classification characteristic. In De Jussieu's system (1789), he followed Ray, arranging his Monocotyledones into three classes based on stamen position and placing them between Acotyledones and Dicotyledones. De Candolle's system (1813) which was to predominate thinking through much of the 19th century used a similar general arrangement, with two subgroups of his ''Monocotylédonés'' (Monocotyledoneae). Lindley (1830) followed De Candolle in using the terms Monocotyledon and Endogenae interchangeably. They considered the monocotyledons to be a group of vascular plants (''Vasculares'') whose vascular bundles were thought to arise from within (''Endogènes'' or
endogenous Endogeny, in biology, refers to the property of originating or developing from within an organism, tissue, or cell. For example, ''endogenous substances'', and ''endogenous processes'' are those that originate within a living system (e.g. an ...
). Monocotyledons remained in a similar position as a major division of the flowering plants throughout the nineteenth century, with minor variations.
George Bentham George Bentham (22 September 1800 – 10 September 1884) was an English botanist, described by the weed botanist Duane Isely as "the premier systematic botanist of the nineteenth century". Born into a distinguished family, he initially studie ...
and Hooker (1862–1883) used Monocotyledones, as would Wettstein, while August Eichler used Mononocotyleae and Engler, following de Candolle, Monocotyledoneae. In the twentieth century, some authors used alternative names such as Bessey's (1915) Alternifoliae and Cronquist's (1966) Liliatae. Later (1981) Cronquist changed Liliatae to Liliopsida, usages also adopted by Takhtajan simultaneously. Thorne (1992) and Dahlgren (1985) also used Liliidae as a synonym. Taxonomists had considerable latitude in naming this group, as the Monocotyledons were a group above the rank of family. Article 16 of the '' ICBN'' allows either a descriptive botanical name or a name formed from the name of an included family. In summary they have been variously named, as follows: * class Monocotyledoneae in the de Candolle system and the Engler system * class Monocotyledones in the Bentham & Hooker system and the Wettstein system * class Monocotyleae in the Eichler system * class Liliatae then Liliopsida in the
Takhtajan system A list of systems of plant taxonomy, system of plant taxonomy, the Takhtajan system of plant classification was published by Armen Takhtajan, in several versions from the 1950s onwards. It is usually compared to the Cronquist system. It admits Para ...
and the
Cronquist system The Cronquist system is a list of systems of plant taxonomy, taxonomic classification system of angiosperms, flowering plants. It was developed by Arthur Cronquist in a series of monographs and texts, including ''The Evolution and Classification of ...
* subclass Liliidae in the Dahlgren system and the Thorne system


Modern era

Over the 1980s, a more general review of the classification of angiosperms was undertaken. The 1990s saw considerable progress in plant
phylogenetics In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
and
cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...
theory, initially based on '' rbcL'' gene sequencing and cladistic analysis, enabling a
phylogenetic tree A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In ...
to be constructed for the flowering plants. The establishment of major new
clades In biology, a clade (), also known as a monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach to taxonomy ...
necessitated a departure from the older but widely used classifications such as Cronquist and Thorne, based largely on morphology rather than genetic data. These developments complicated discussions on plant evolution and necessitated a major taxonomic restructuring. This
DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
based
molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
research confirmed on the one hand that the monocots remained as a well defined
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
group or
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
, in contrast to the other historical divisions of the flowering plants, which had to be substantially reorganized. No longer could the angiosperms be simply divided into monocotyledons and dicotyledons; it was apparent that the monocotyledons were but one of a relatively large number of defined groups within the angiosperms. Correlation with morphological criteria showed that the defining feature was not cotyledon number but the separation of angiosperms into two major
pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
types, uniaperturate ( monosulcate and monosulcate-derived) and triaperturate (tricolpate and tricolpate-derived), with the monocots situated within the uniaperturate groups. The formal taxonomic ranking of Monoctyledons thus became replaced with monocots as an informal clade. This is the name that has been most commonly used since the publication of the Angiosperm Phylogeny Group (APG) system in 1998 and regularly updated since. Within the angiosperms, there are two major grades, a small early branching basal grade, the
basal angiosperms The basal angiosperms are the flowering plants which diverged from the lineage leading to most flowering plants. In particular, the most basal angiosperms were called the ANITA grade, which is made up of ''Amborella'' (a single species of shrub f ...
(ANA grade) with three lineages and a larger late branching grade, the core angiosperms (mesangiosperms) with five lineages, as shown in the
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
.


Subdivision

While the monocotyledons have remained extremely stable in their outer borders as a well-defined and coherent monophylectic group, the deeper internal relationships have undergone considerable flux, with many competing classification systems over time. Historically, Bentham (1877), considered the monocots to consist of four alliances, Epigynae, Coronariae, Nudiflorae and Glumales, based on floral characteristics. He describes the attempts to subdivide the group since the days of Lindley as largely unsuccessful. Like most subsequent classification systems it failed to distinguish between two major orders,
Liliales Liliales is an order (biology), order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web List of systems of plant classification, system, within the lilioid monocots. This order of necessity includ ...
and
Asparagales Asparagales (asparagoid lilies) are a diverse order of flowering plants in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 genera, and about 36,00 ...
, now recognised as quite separate. A major advance in this respect was the work of Rolf Dahlgren (1980), which would form the basis of the Angiosperm Phylogeny Group's (APG) subsequent modern classification of monocot families. Dahlgren who used the alternate name Lilliidae considered the monocots as a subclass of angiosperms characterised by a single cotyledon and the presence of triangular protein bodies in the sieve tube plastids. He divided the monocots into seven superorders, Alismatiflorae, Ariflorae, Triuridiflorae, Liliiflorae, Zingiberiflorae, Commeliniflorae and Areciflorae. With respect to the specific issue regarding Liliales and Asparagales, Dahlgren followed Huber (1969) in adopting a splitter approach, in contrast to the longstanding tendency to view Liliaceae as a very broad sensu lato
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
. Following Dahlgren's untimely death in 1987, his work was continued by his widow, Gertrud Dahlgren, who published a revised version of the classification in 1989. In this scheme the
suffix In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns and adjectives, and verb endings, which form the conjugation of verbs. Suffixes can ca ...
''-florae'' was replaced with ''-anae'' (''e.g.'' Alismatanae) and the number of superorders expanded to ten with the addition of Bromelianae, Cyclanthanae and Pandananae. Molecular studies have both confirmed the
monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...
of the monocots and helped elucidate relationships within this group. The APG system does not assign the monocots to a taxonomic rank, instead recognizing a monocots clade. However, there has remained some uncertainty regarding the exact relationships between the major lineages, with a number of competing models (including APG). The APG system establishes eleven orders of monocots. These form three grades, the alismatid monocots,
lilioid monocots Lilioid monocots (lilioids, liliid monocots, petaloid monocots, petaloid lilioid monocots) is an informal name used for a grade (biology), grade (grouping of taxa with common characteristics) of five monocot order (biology), orders (Petrosavial ...
and the commelinid monocots by order of branching, from early to late. In the following
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
numbers indicate
crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor ...
(most recent common ancestor of the sampled species of the clade of interest) divergence times in mya (million years ago). Of some 70,000
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), ...
, by far the largest number (65%) are found in two families, the orchids and grasses. The orchids (
Orchidaceae Orchids are plants that belong to the family (biology), family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan distribution, cosmopolitan plants that ...
,
Asparagales Asparagales (asparagoid lilies) are a diverse order of flowering plants in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 genera, and about 36,00 ...
) contain about 25,000 species and the grasses (
Poaceae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...
,
Poales The Poales are a large order (biology), order of flowering plants in the monocotyledons, and includes families of plants such as the Poaceae, grasses, bromeliads, Juncaceae, rushes and Cyperaceae, sedges. 14 plant families are currently recogniz ...
) about 11,000. Other well known groups within the Poales order include the
Cyperaceae The Cyperaceae () are a family of graminoid (grass-like), monocotyledonous flowering plants known as wikt:sedge, sedges. The family (biology), family is large; botanists have species description, described some 5,500 known species in about 90 ...
(sedges) and Juncaceae (rushes), and the monocots also include familiar families such as the palms (
Arecaceae The Arecaceae () is a family (biology), family of perennial plant, perennial, flowering plants in the Monocotyledon, monocot order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, all commonly k ...
, Arecales) and lilies ( Liliaceae,
Liliales Liliales is an order (biology), order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web List of systems of plant classification, system, within the lilioid monocots. This order of necessity includ ...
).


Evolution

In prephyletic classification systems monocots were generally positioned between plants other than angiosperms and dicots, implying that monocots were more primitive. With the introduction of phyletic thinking in taxonomy (from the system of Eichler 1875–1878 onwards) the predominant theory of monocot origins was the ranalean (ranalian) theory, particularly in the work of Bessey (1915), which traced the origin of all flowering plants to a Ranalean type, and reversed the sequence making dicots the more primitive group. The monocots form a
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
group arising early in the history of the
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, but the fossil record is meagre. The earliest fossils presumed to be monocot remains date from the
early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
period. For a very long time,
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s of palm trees were believed to be the oldest monocots, first appearing 90 million years ago ( mya), but this estimate may not be entirely true. At least some putative monocot fossils have been found in strata as old as the eudicots. The oldest fossils that are unequivocally monocots are pollen from the Late
Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...
Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...
– Early
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
period, about 120-110 million years ago, and are assignable to
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
- Pothoideae-Monstereae Araceae; being Araceae, sister to other Alismatales. They have also found flower fossils of Triuridaceae (Pandanales) in Upper Cretaceous rocks in New Jersey, becoming the oldest known sighting of
saprophytic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ...
/ mycotrophic habits in
angiosperm 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 ...
plants and among the oldest known fossils of monocotyledons. Topology of the angiosperm
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
tree could imply that the monocots are among the oldest lineages of angiosperms, which would support the theory that they are just as old as the eudicots. The pollen of the eudicots dates back 125 million years, so the lineage of monocots should be that old too.


Molecular clock estimates

Kåre Bremer, using rbcL sequences and the mean path length method for estimating divergence times, estimated the age of the monocot crown group (i.e. the time at which the ancestor of today's ''Acorus'' diverged from the rest of the group) as 134 million years. Similarly, Wikström ''et al.'', using Sanderson's non-parametric rate smoothing approach, obtained ages of 127–141 million years for the crown group of monocots. All these estimates have large error ranges (usually 15–20%), and Wikström ''et al.'' used only a single calibration point, namely the split between Fagales and
Cucurbitales The Cucurbitales are an order of flowering plants, included in the rosid group of dicotyledons. This order mostly belongs to tropical areas, with limited presence in subtropical and temperate regions. The order includes shrubs and trees, togeth ...
, which was set to 84 Ma, in the late
Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya ( million years ago) and 83.6 ± 0.7 m ...
period. Early molecular clock studies using strict clock models had estimated the monocot crown age to 200 ± 20 million years ago or 160 ± 16 million years, while studies using relaxed clocks have obtained 135-131 million years or 133.8 to 124 million years. Bremer's estimate of 134 million years has been used as a secondary calibration point in other analyses. Some estimates place the diversification of the monocots as far back as 150 mya in the
Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
period. The lineage that led to monocots (stem group) split from other plants about 136 million years ago or 165–170 million years ago.


Core group

The age of the core group of so-called 'nuclear monocots' or 'core monocots', which correspond to all orders except Acorales and Alismatales, is about 131 million years to present, and crown group age is about 126 million years to the present. The subsequent branching in this part of the tree (i.e. Petrosaviaceae, Dioscoreales + Pandanales and
Liliales Liliales is an order (biology), order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web List of systems of plant classification, system, within the lilioid monocots. This order of necessity includ ...
clades appeared), including the crown Petrosaviaceae group may be in the period around 125–120 million years BC (about 111 million years so far), and stem groups of all other orders, including Commelinidae would have diverged about or shortly after 115 million years. These and many clades within these orders may have originated in southern
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
, i.e. Antarctica, Australasia, and southern South America.


Aquatic monocots

The aquatic monocots of Alismatales have commonly been regarded as "primitive". They have also been considered to have the most primitive foliage, which were cross-linked as Dioscoreales and
Melanthiales Melanthiales Johann Heinrich Friedrich Link, Link (melanthoid lilies) was an Order (biology), order of monocotyledons, whose name and botanical authority is derived by typification from the description of the Type (biology), type Family (biology), ...
. Keep in mind that the "most primitive" monocot is not necessarily "the sister of everyone else". This is because the ancestral or primitive characters are inferred by means of the reconstruction of character states, with the help of the phylogenetic tree. So primitive characters of monocots may be present in some derived groups. On the other hand, the basal taxa may exhibit many morphological autapomorphies. So although Acoraceae is the sister group to the remaining monocotyledons, the result does not imply that Acoraceae is "the most primitive monocot" in terms of its character states. In fact, Acoraceae is highly derived in many morphological characters, and that is precisely why Acoraceae and Alismatales occupied relatively derived positions in the trees produced by Chase ''et al.'' and others. Some authors support the idea of an aquatic phase as the origin of monocots. The phylogenetic position of Alismatales (many water), which occupy a relationship with the rest except the Acoraceae, do not rule out the idea, because it could be 'the most primitive monocots' but not 'the most basal'. The Atactostele stem, the long and linear leaves, the absence of secondary growth (see the
biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to Organ (anatomy), organs, Cell (biology), cells and cell organelles, using the methods of mechani ...
of living in the water), roots in groups instead of a single root branching (related to the nature of the substrate), including
sympodial In botany, sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, als ...
use, are consistent with a water source. However, while monocots were sisters of the aquatic Ceratophyllales, or their origin is related to the adoption of some form of aquatic habit, it would not help much to the understanding of how it evolved to develop their distinctive anatomical features: the monocots seem so different from the rest of angiosperms and it's difficult to relate their morphology, anatomy and development and those of broad-leaved angiosperms.


Other taxa

In the past, taxa which had petiolate leaves with reticulate venation were considered "primitive" within the monocots, because of the superficial resemblance to the leaves of dicotyledons. Recent work suggests that while these taxa are sparse in the phylogenetic tree of monocots, such as fleshy fruited taxa (excluding taxa with aril seeds dispersed by ants), the two features would be adapted to conditions that evolved together regardless. Among the taxa involved were '' Smilax'', ''
Trillium ''Trillium'' (trillium, wakerobin, toadshade, tri flower, birthroot, birthwort, and sometimes "wood lily") is a genus of about fifty flowering plant species in the family Melanthiaceae. ''Trillium'' species are native to temperate regions of No ...
'' (Liliales), '' Dioscorea'' (Dioscoreales), etc. A number of these plants are
vine A vine 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 themselves, for instance, when used in wicker work.Jackson; Benjamin; Da ...
s that tend to live in shaded habitats for at least part of their lives, and this fact may also relate to their shapeless
stomata In botany, a stoma (: stomata, from Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spa ...
. Reticulate venation seems to have appeared at least 26 times in monocots, and fleshy fruits have appeared 21 times (sometimes lost later); the two characteristics, though different, showed strong signs of a tendency to be good or bad in tandem, a phenomenon described as "concerted convergence" ("coordinated convergence").


Etymology

The name monocotyledons is derived from the traditional botanical name "Monocotyledones" or ''Monocotyledoneae'' in
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
, which refers to the fact that most members of this group have one
cotyledon A cotyledon ( ; ; "a cavity, small cup, any cup-shaped hollow", gen. (), ) is a "seed leaf" – a significant part of the embryo within the seed of a plant – and is formally defined as "the embryonic leaf in seed-bearing plants, one or mor ...
, or embryonic leaf, in their
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s.


Ecology


Emergence

Some monocots, such as grasses, have hypogeal emergence, where the mesocotyl elongates and pushes the coleoptile (which encloses and protects the shoot tip) toward the soil surface. Since elongation occurs above the cotyledon, it is left in place in the soil where it was planted. Many dicots have epigeal emergence, in which the hypocotyl elongates and becomes arched in the soil. As the hypocotyl continues to elongate, it pulls the cotyledons upward, above the soil surface.


Conservation

The
IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...
Red List describes four species as
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
, four as extinct in the wild, 626 as possibly extinct, 423 as
critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
, 632
endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...
, 621 vulnerable, and 269
near threatened A near-threatened species is a species which has been Conservation status, categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature (IUCN) as that may be vulnerable to Endangered species, endangerment in the ne ...
of 4,492 whose status is known.


Uses

Monocots are among the most important plants economically and culturally, and account for most of the staple foods of the world, such as
cereal A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize ( Corn). Edible grains from other plant families, ...
grains A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and le ...
and starchy root crops, and palms, orchids and lilies, building materials, and many medicines. Of the monocots, the grasses are of enormous economic importance as a source of animal and human food, and form the largest component of agricultural species in terms of
biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...
produced. Other economically important monocotyledon crops include various palms (
Arecaceae The Arecaceae () is a family (biology), family of perennial plant, perennial, flowering plants in the Monocotyledon, monocot order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, all commonly k ...
), bananas and plantains ( Musaceae),
ginger Ginger (''Zingiber officinale'') is a flowering plant whose rhizome, ginger root or ginger, is widely used as a spice and a folk medicine. It is an herbaceous perennial that grows annual pseudostems (false stems made of the rolled bases of l ...
s and their relatives,
turmeric Turmeric (), or ''Curcuma longa'' (), is a flowering plant in the ginger family Zingiberaceae. It is a perennial, rhizomatous, herbaceous plant native to the Indian subcontinent and Southeast Asia that requires temperatures between and high ...
and
cardamom Cardamom (), sometimes cardamon or cardamum, is a spice made from the seeds of several plants in the genus (biology), genera ''Elettaria'' and ''Amomum'' in the family Zingiberaceae. Both genera are native to the Indian subcontinent and Indon ...
(
Zingiberaceae Zingiberaceae () or the ginger family is a family of flowering plants made up of about 50 genera with a total of about 1600 known species of aromatic perennial herbs with creeping horizontal or tuberous rhizomes distributed throughout tropical ...
),
asparagus Asparagus (''Asparagus officinalis'') is a perennial flowering plant species in the genus ''Asparagus (genus), Asparagus'' native to Eurasia. Widely cultivated as a vegetable crop, its young shoots are used as a spring vegetable. Description ...
(
Asparagaceae Asparagaceae (), known as the asparagus family, is a family of flowering plants, placed in the order Asparagales of the monocots. The family name is based on the edible garden asparagus, '' Asparagus officinalis''. This family includes both ...
),
pineapple The pineapple (''Ananas comosus'') is a Tropical vegetation, tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been culti ...
( Bromeliaceae), sedges (
Cyperaceae The Cyperaceae () are a family of graminoid (grass-like), monocotyledonous flowering plants known as wikt:sedge, sedges. The family (biology), family is large; botanists have species description, described some 5,500 known species in about 90 ...
) and rushes ( Juncaceae),
vanilla Vanilla is a spice derived from orchids of the genus ''Vanilla (genus), Vanilla'', primarily obtained from pods of the flat-leaved vanilla (''Vanilla planifolia, V. planifolia''). ''Vanilla'' is not Autogamy, autogamous, so pollination ...
(
Orchidaceae Orchids are plants that belong to the family (biology), family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan distribution, cosmopolitan plants that ...
), yam ( Dioscoreaceae),
taro Taro (; ''Colocasia esculenta'') is a root vegetable. It is the most widely cultivated species of several plants in the family Araceae that are used as vegetables for their corms, leaves, stems and Petiole (botany), petioles. Taro corms are a ...
(
Araceae The Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe (or leaf-like bract). Also ...
), and
leek A leek is a vegetable, a cultivar of ''Allium ampeloprasum'', the broadleaf wild leek (synonym (taxonomy), syn. ''Allium porrum''). The edible part of the plant is a bundle of Leaf sheath, leaf sheaths that is sometimes erroneously called a "s ...
s,
onion An onion (''Allium cepa'' , from Latin ), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus '' Allium''. The shallot is a botanical variety of the onion which was classifie ...
and
garlic Garlic (''Allium sativum'') is a species of bulbous flowering plants in the genus '' Allium''. Its close relatives include the onion, shallot, leek, chives, Welsh onion, and Chinese onion. Garlic is native to central and south Asia, str ...
(
Amaryllidaceae The Amaryllidaceae are a family of herbaceous, mainly perennial and bulbous (rarely rhizomatous) flowering plants in the monocot order Asparagales. The family takes its name from the genus '' Amaryllis'' and is commonly known as the amaryl ...
). Many
houseplant A houseplant, also known as a pot plant, potted plant, or indoor plant, is an ornamental plant cultivated indoors. for aesthetic or practical purposes. These plants are commonly found in House, homes, Office, offices, and various indoor spaces, w ...
s are monocotyledon
epiphyte 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 ...
s. Most of the horticultural bulbs, plants cultivated for their blooms, such as lilies, daffodils, irises, amaryllis, cannas, bluebells and
tulip Tulips are spring-blooming perennial herbaceous bulbiferous geophytes in the ''Tulipa'' genus. Their flowers are usually large, showy, and brightly coloured, generally red, orange, pink, yellow, or white. They often have a different colour ...
s, are monocotyledons.


See also

* Monocotyledon reproduction


Notes


Citations


Bibliography


Books


Historical

* * * * * * * * * * * * * * * * * ** , see also *


Modern

* * *
1st edition
* * * * * * * * * * * * * * * * * * * See als
ebook 2010
* * * * * * * * * * (''see also''
Excerpts at Amazon
* * * *


Symposia

* * * *
Excerpts
* *


Chapters

* , in * , In . * , in * , In * , in * , in * , In * , in * In * In * , In . * , in *, in *, in * in * , In * In * , in * , In .


Articles

* * (also at ) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


Phylogenetics

* * * * * * * * * * * * * * * * * * * * * * * * *


APG

* * * * * *


Websites and databases

* * (''see also'' Angiosperm Phylogeny Website) * * * * * *


External links

* * {{Authority control Plant unranked clades Early Cretaceous plants Extant Early Cretaceous first appearances