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Monocotyledons (), commonly referred to as monocots, (
Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank (botany), rank higher than that of order (biology), order) of flowering plants. Such a superorder of necessity includes the Type (biology), type Family (biol ...
''
sensu ''Sensu'' is a Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Ro ...
'' Chase & Reveal) are
grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain ...

grass
and grass-like
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s (angiosperms), the
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
s of which typically contain only one
embryo An embryo is the early stage of development of a multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms ar ...
nic leaf, or
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germination, germinating see ...
. They constitute one of the major groups into which the flowering plants have traditionally been divided, the rest of the flowering plants having two cotyledons and therefore classified as
dicotyledon The dicotyledons, also known as dicots (or more rarely dicotyls), are one of the two groups into which all the flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte ...
s, or dicots. Monocotyledons have almost always been recognized as a group, but with various
taxonomic ranks Taxonomy (general) Taxonomy is the practice and science of categorization or classification (general theory), classification based on Isolated point#Discrete set, discrete sets. A Taxonomy (general), taxonomy (or taxinomical classification) i ...
and under several different names. The
APG III system The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a fu ...
of 2009 recognises a clade called "monocots" but does not assign it to a taxonomic rank. The monocotyledons include about 60,000 species. The largest
family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politic ...
in this group (and in the flowering plants as a whole) by number of species are the orchids (family
Orchidaceae Orchidaceae ( ), common name, commonly called the orchid family, is a diverse and widespread family (biology), family of flowering plants, with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two la ...

Orchidaceae
), with more than 20,000 species. About half as many species belong to the true grasses (
Poaceae Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain ...
), which are economically the most important family of monocotyledons. Often mistaken for grasses,
sedges The Cyperaceae are a family of graminoid In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in t ...
are also monocots. In
agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors su ...

agriculture
the majority of the
biomass Biomass is plant or animal material used as fuel to produce electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position ...

biomass
produced comes from monocotyledons. These include not only major
grains A grain is a small, hard, dry – with or without an attached or layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are s and . After being harvested, dry ...

grains
(
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
,
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
,
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It can also be ...

maize
, etc.), but also
forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing In agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentism, se ...

forage
grasses,
sugar cane Sugarcane or sugar cane is a species of (often hybrid) tall, perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, ...

sugar cane
, and the
bamboo Bamboos are a diverse group of evergreen In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in th ...

bamboo
s. Other economically important monocotyledon
crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. Crops may refer either to the harvested parts or to the harvest in a more refined state. Most crops are cultivated in agriculture Agriculture is the ...

crops
include various palms (
Arecaceae The Arecaceae is a family (biology), family of Perennial plant, perennial flowering plants in the Monocotyledon, monocot order (biology), order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, a ...

Arecaceae
), bananas and plantains (
Musaceae Musaceae is a family (biology), family of flowering plants composed of three genera with ca 91 known species, placed in the Order (biology), order Zingiberales. The family is native to the tropics of Africa and Asia. The plants have a large herbac ...
),
ginger Ginger (''Zingiber officinale'') is a flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: ...

ginger
s and their relatives,
turmeric Turmeric (pronounced , also ) is a flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: ...
and
cardamom Cardamom (), sometimes cardamon or cardamum, is a spice A spice is a seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Reco ...

cardamom
(
Zingiberaceae Zingiberaceae () or the ginger family is a of s made up of about 50 with a total of about 1600 known of aromatic s with creeping horizontal or tuberous s distributed throughout tropical Africa, Asia, and the Americas. Members of the family Zi ...
),
asparagus Asparagus, or garden asparagus, folk name sparrow grass, scientific name ''Asparagus officinalis'', is a perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic eukaryotes of the Kingdom ...

asparagus
(
Asparagaceae Asparagaceae is a Family (biology), family of flowering plants, placed in the Order (biology), order Asparagales of the monocots. Its best known member is ''Asparagus officinalis'', garden asparagus. Taxonomy In earlier classification systems, ...
),
pineapple The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit and is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many centurie ...

pineapple
(
Bromeliaceae The Bromeliaceae (the bromeliads) is a family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its m ...

Bromeliaceae
), sedges (
Cyperaceae The Cyperaceae are a family of graminoid (grass-like), monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank higher than tha ...
) and rushes (
Juncaceae Juncaceae is a family of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (biology), families, approxim ...
), and
leek The leek is a vegetable Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including t ...

leek
s,
onion The onion (''Allium cepa'' L., from Latin ''cepa'' "onion"), also known as the bulb onion or common onion, is a vegetable Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still co ...

onion
and
garlic Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to Central ...

garlic
(
Amaryllidaceae The Amaryllidaceae are a family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, ty ...

Amaryllidaceae
). Many
houseplant A houseplant is a plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, th ...

houseplant
s are monocotyledon
epiphytes 200px, '' Tillandsia bourgaei'' growing on an oak tree in Mexico An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating a ...

epiphytes
. Additionally most of the
horticultural Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists grow flowers, fruits and nuts, vegetables and herbs, as well as ornamental trees and lawns. ...
bulbs In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the A ...

bulbs
, plants cultivated for their blooms, such as
lilies ''Lilium'' is a genus of Herbaceous plant, herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in much o ...

lilies
,
daffodil ''Narcissus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

daffodil
s,
iris
iris
es,
amaryllis ''Amaryllis'' () is the only genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxon ...

amaryllis
, cannas,
bluebells
bluebells
and
tulip Tulips (''Tulipa'') are a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, inclu ...

tulip
s, are monocotyledons.


Description


General

The monocots or monocotyledons have, as the name implies, a single (mono-)
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germination, germinating see ...
, or embryonic leaf, in their
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
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 plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte ...
s or dicots which typically have two cotyledons; however modern research has shown that the dicots are not a natural group, and the term can only be used to indicate all angiosperms that are not monocots and is used in that respect here. 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, ''Bauplan'' (German plural ''Baupläne''), or ground plan is a set of morphological features common to many members of a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ) ...
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 Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and f ...
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. However, morphological features that reliably characterise major
clades A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual cont ...
are rare. Thus monocots are distinguishable from other angiosperms both in terms of their uniformity and diversity. On the one hand the organisation of the shoots, leaf structure and floral configuration are more uniform than in the remaining angiosperms, yet within these constraints a wealth of diversity exists, indicating a high degree of evolutionary success. Monocot
diversity Diversity, diversify, or diverse may refer to: Business *Diversity (business) The "business case for diversity" stems from the progression of the models of diversity within the workplace since the 1960s. The original model for diversity was situ ...
includes
perennial A perennial plant or simply perennial is a plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, thr ...
geophytes A storage organ is a part of a plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical ene ...
such as ornamental flowers including
orchids Orchidaceae ( ), commonly called the orchid family, is a diverse and widespread family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social ...

orchids
(
Asparagales Asparagales (asparagoid lilies) is an order (biology), order of plants in modern classification systems such as the Angiosperm Phylogeny Group (APG) and the Angiosperm Phylogeny Web. The order takes its name from the type (biology), type family ...
);
tulips Tulips (''Tulipa'') are a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, inclu ...

tulips
and
lilies ''Lilium'' is a genus of Herbaceous plant, herbaceous flowering plants growing from bulbs, all with large prominent flowers. They are the true lilies. Lilies are a group of flowering plants which are important in culture and literature in much o ...

lilies
(
Liliales Liliales is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and ...
); rosette and succulent
epiphytes 200px, '' Tillandsia bourgaei'' growing on an oak tree in Mexico An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating a ...

epiphytes
(Asparagales); mycoheterotrophs (Liliales,
Dioscoreales The Dioscoreales are an order of monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank higher than that of order) of floweri ...
,
Pandanales Pandanales, the pandans or screw-pines, is an of s placed in the in the and . Within the monocots Pandanales are grouped in the where they are in a relationship with the . Historically the order has consisted of a number of different in ...
), all in the
lilioid monocots Lilioid monocots (lilioids, liliid monocots, petaloid monocots, petaloid lilioid monocots) is an informal name used for a grade Grade or grading may refer to: Arts and entertainment * Grade (band) Grade is a melodic hardcore band from Canada ...
; major
cereal A cereal is any Poaceae, grass cultivated (grown) for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, cereal germ, germ, and bran. The term may also refer to the resulting grain ...

cereal
grains A grain is a small, hard, dry seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double albu ...
(
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It can also be ...

maize
,
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
,
barley Barley (''Hordeum vulgare''), a member of the grass family Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people related either by consanguinity (by recogn ...

barley
,
rye Rye (''Secale cereale'') is a grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationshi ...

rye
,
oats The oat (''Avena sativa''), sometimes called the common oat, is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A spec ...

oats
,
millet Millets () are a group of highly variable small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Millets are important crops in the semiarid tropics of Asia and Africa (especially in Indi ...

millet
,
sorghum ''Sorghum'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circum ...

sorghum
and
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
) in the
grass family Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). ...
; and forage grasses (
Poales The Poales are a large order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or wa ...
) as well as woody tree-like
palm trees
palm trees
(
Arecales Arecales is an order Order, ORDER or Orders may refer to: * Orderliness Orderliness is a quality that is characterized by a person’s interest in keeping their surroundings and themselves well organized, and is associated with other qualiti ...

Arecales
),
bamboo Bamboos are a diverse group of evergreen In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in th ...

bamboo
,
reed Reed or Reeds may refer to: Science, technology, biology, and medicine * Reed bird (disambiguation) Reed bird may refer to: * Reed bunting * Pallas's reed bunting * Eurasian reed warbler * Red nose flower bomb ... * Reed pen A reed pen ( ...
s and
bromeliads The Bromeliaceae (the bromeliads) is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of familie ...

bromeliads
(Poales),
bananas A banana is an elongated, edible fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who special ...

bananas
and
ginger Ginger (''Zingiber officinale'') is a flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: ...

ginger
(
Zingiberales The Zingiberales are flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything ...
) in the
commelinid monocots In plant taxonomy, commelinids (originally commelinoids) (plural, not capitalised) is a clade of flowering plants within the monocots, distinguished by having cell walls containing ferulic acid. The commelinids are the only clade that the APG IV ...
, as well as both emergent (Poales,
Acorales ''Acorus'' is a genus of monocot flowering plants. This genus was once placed within the family Araceae (aroids), but more recent classifications place it in its own family Acoraceae and order Acorales, of which it is the sole genus of the oldes ...
) and
aroids The Araceae are a family (biology), family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix (botany), spadix is usually accompanied by, and sometimes partially enclosed in, ...
, as well as floating or submerged
aquatic plants Aquatic plants are plants that have adapted to living in aquatic environments (seawater, saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a pl ...

aquatic plants
such as
seagrass Seagrasses are the only flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anyt ...

seagrass
(
Alismatales The Alismatales (alismatids) are an order of flowering plants including about 4500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Description The Alismatales comprise ...
).


Vegetative

;Organisation, growth and life forms The most important distinction is their growth pattern, lacking a lateral meristem (
cambium A cambium (plural cambia or cambiums), in plants, is a tissue layer that provides partially undifferentiated cells for plant growth. It is found in the area between xylem Xylem is one of the two types of transport tissue Tissue may refer to: ...
) that allows for continual growth in diameter with height (
secondary growth In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Anc ...
), and therefore this characteristic is a basic limitation in shoot construction. Although largely herbaceous, some
arboraceous A woody plant is a plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, ...
monocots reach great height, length and mass. The latter include
agaves ''Agave'' (, , ) is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

agaves
, palms, pandans, and
bamboos
bamboos
. This creates challenges in water transport that monocots deal with in various ways. Some, such as species of ''
Yucca ''Yucca'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscr ...

Yucca
'', develop anomalous secondary growth, while palm trees utilise an anomalous primary growth form described as establishment growth (''see''
Vascular system The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is a group of organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many o ...
). 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 200px, '' Tillandsia bourgaei'' growing on an oak tree in Mexico An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating a ...
orchids Orchidaceae ( ), commonly called the orchid family, is a diverse and widespread family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social ...

orchids
(Asparagales) and
bromeliads The Bromeliaceae (the bromeliads) is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of familie ...

bromeliads
(Poales) to submarine
Alismatales The Alismatales (alismatids) are an order of flowering plants including about 4500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Description The Alismatales comprise ...
(including the reduced
Lemnoideae Lemnoideae is a subfamily of flowering aquatic plant Aquatic plants are plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things th ...

Lemnoideae
) and mycotrophic
Burmanniaceae Burmanniaceae is a family In human society, family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of families is to maintain the ...
(Dioscreales) and
Triuridaceae Triuridaceae are a family of tropical and subtropical flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family ...
(Pandanales). Other forms of adaptation include the climbing vines of Araceae (Alismatales) which use negative phototropism (skototropism) to locate host (biology), host trees (''i.e.'' the darkest area), while some palms such as ''Calamus (palm), Calamus manan'' (
Arecales Arecales is an order Order, ORDER or Orders may refer to: * Orderliness Orderliness is a quality that is characterized by a person’s interest in keeping their surroundings and themselves well organized, and is associated with other qualiti ...

Arecales
) produce the longest shoots in the plant kingdom, up to 185 m long. Other monocots, particularly
Poales The Poales are a large order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or wa ...
, have adopted a therophyte life form.


Leaves

The cotyledon, the primordial Angiosperm leaf 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 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 stolon, runners and rhizomes, 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 A storage organ is a part of a plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical ene ...
(Tillich, Figure 11). Other geophytes develop
bulbs In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the A ...

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 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 wikt:geophilous, geophilous shoots (Tillich, Figure 11) that help overcome the limited trunk stability of large woody monocots.


Reproductive

;Flowers In nearly all cases the perianth, perigone consists of two alternating trimerous whorl (biology), whorls of tepals, being wikt:homochlamydeous, homochlamydeous, without differentiation between calyx (flower), calyx and corolla (flower), corolla. In wikt:zoophilous, zoophilous (pollinated by animals) taxa, both whorls are corolline (petal-like). Anthesis (the period of flower opening) is usually wikt:fugacious, 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. These plants need to advertise to pollinators and do so by way of Glossary of botanical terms#phaneranthous, 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 stamen, filaments, staminodes or stylodia which have become modified to attract pollinators). However, some monocot plants may have Glossary of botanical terms#aphananthous, 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#Plant embryos, embryo 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. 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. 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'', ''Smilax'' (greenbriar), ''Pogonia (plant), Pogonia'' (an orchid), and the
Dioscoreales The Dioscoreales are an order of monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank higher than that of order) of floweri ...
(yams). ''Potamogeton'' and ''Paris quadrifolia'' (herb-paris) are examples of monocots with tetramerous flowers. Other plants exhibit a mixture of characteristics. Nymphaeaceae (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 Glossary of botanical terms#apomorphy, apomorphies (characteristics derived during
radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and f ...
rather than inherited from an ancestral form) include herbaceous habit, leaves with parallel venation and sheathed base, an embryo with a single cotyledon, an stele (biology), atactostele, numerous adventitious roots, sympodial growth, and trimerous (3 parts per whorl (botany), 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 wall formation* # Successive microsporogenesis # Syncarpous gynoecium # Parietal placentation # Monocotyledonous seedling # Persistent radicle # :wikt:Haustorium, Haustorial cotyledon tip # Open cotyledon sheath # Steroidal saponins* # Fly pollination* # Diffuse vascular bundles and absence of
secondary growth In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Anc ...


Vascular system

Monocots have a distinctive arrangement of vascular tissue known as an Stele (biology), 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 and do not have the ability to increase the width of a stem (
secondary growth In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Anc ...
) via the same kind of vascular cambium found in non-monocot woody plants. However, some monocots do have secondary growth; because this does not arise from a single vascular cambium producing xylem 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 (biology), order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, a ...

Arecaceae
), screwpines (Pandanaceae), bananas (
Musaceae Musaceae is a family (biology), family of flowering plants composed of three genera with ca 91 known species, placed in the Order (biology), order Zingiberales. The family is native to the tropics of Africa and Asia. The plants have a large herbac ...
), ''
Yucca ''Yucca'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscr ...

Yucca
'', ''Aloe'', ''Dracaena (plant), Dracaena'', and ''Cordyline''.


Taxonomy

The monocots form one of five major lineages of mesangiosperms (core angiosperms), which in themselves form 99.95% of all angiosperms. The monocots and the eudicots, are the largest and most diversified angiosperm radiations accounting for 22.8% and 74.2% of all angiosperm species respectively. Of these, the grass family (Poaceae) is the most economically important, which together with the orchids
Orchidaceae Orchidaceae ( ), common name, commonly called the orchid family, is a diverse and widespread family (biology), family of flowering plants, with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two la ...

Orchidaceae
account for half of the species diversity, accounting for 34% and 17% of all monocots respectively and are among the largest families of angiosperms. They are also among the dominant members of many plant communities.


Early history


Pre-Linnean

The monocots are one of the major divisions of the
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s or angiosperms. They have been recognized as a natural group since the sixteenth century when Lobelius (1571), searching for a characteristic to group plants by, decided on leaf form and their venation (botany), venation. He observed that the majority had broad leaves with net-like venation, but a smaller group were grass-like plants with long straight parallel veins. In doing so he distinguished between the dicotyledons, and the latter (grass-like) monocotyledon group, although he had no formal names for the two groups. Formal description dates from John Ray's studies of
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
structure in the 17th century. Ray, who is often considered the first botanical systematist, observed the dichotomy of
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germination, germinating see ...
structure in his examination of seeds. He reported his findings in a paper read to the Royal Society 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 enabled Eichler system, Eichler 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 Carl Linnaeus, Linnaeus (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 since then, starting with Antoine Laurent de Jussieu, De Jussieu and Augustin De Candolle, De Candolle, has used Ray's distinction as a major classification characteristic. In De Jussieu system, 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 system, 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). John Lindley, 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). Monocotyledons remained in a similar position as a major division of the flowering plants throughout the nineteenth century, with minor variations. George Bentham and Joseph Dalton Hooker, Hooker (1862–1883) used Monocotyledones, as would Richard Wettstein, Wettstein, while August Eichler used Mononocotyleae and Adolf Engler, Engler, following de Candolle, Monocotyledoneae. In the twentieth century, some authors used alternative names such as Charles Bessey, Bessey's (1915) Alternifoliae and Arthur Cronquist, Cronquist's (1966) Liliatae. Later (1981) Cronquist changed Liliatae to Liliopsida, usages also adopted by Takhtajan simultaneously. Robert F. Thorne, Thorne (1992) and Rolf, 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 and the Cronquist system * subclass Liliidae in the Dahlgren system and the Thorne system (1992), 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 and cladistic theory, initially based on ''rbcL'' gene sequencing and cladistic analysis, enabling a phylogenetic tree to be constructed for the flowering plants. The establishment of major new
clades A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual cont ...
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 based molecular phylogenetic research confirmed on the one hand that the monocots remained as a well defined monophyly, monophyletic group or clade, 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 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, (APG) system in 1998 and regularly updated since. Within the angiosperms, there are two major evolutionary grade, grades, a small early branching basal (phylogenetics), basal grade, the basal angiosperms (ANA grade) with three lineage (evolution), lineages and a larger late branching grade, the core angiosperms (mesangiosperms) with five lineages, as shown in the cladogram.


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, George Bentham, Bentham (1877), considered the monocots to consist of four alliance (taxonomy), alliances, Epigynae, Coronariae, Nudiflorae and Glumales, based on floral characteristics. He describes the attempts to subdivide the group since the days of John Lindley, Lindley as largely unsuccessful. Like most subsequent classification systems it failed to distinguish between two major orders,
Liliales Liliales is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and ...
and
Asparagales Asparagales (asparagoid lilies) is an order (biology), order of plants in modern classification systems such as the Angiosperm Phylogeny Group (APG) and the Angiosperm Phylogeny Web. The order takes its name from the type (biology), type family ...
, 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 (biology), 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 Order (biology), superorders, Alismatiflorae, Ariflorae, Triuridiflorae, Liliiflorae, Zingiberiflorae, Commeliniflorae and Areciflorae. With respect to the specific issue regarding Liliales and Asparagales, Dahlgren followed Herbert Huber (botanist), Huber (1969) in adopting a Lumpers and splitters, splitter approach, in contrast to the longstanding tendency to view Liliaceae as a very broad sensu lato
family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politic ...
. 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 ''-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 of the monocots and helped elucidate relationships within this group. The Angiosperm Phylogeny Group, 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 Grade or grading may refer to: Arts and entertainment * Grade (band) Grade is a melodic hardcore band from Canada ...
and the
commelinid monocots In plant taxonomy, commelinids (originally commelinoids) (plural, not capitalised) is a clade of flowering plants within the monocots, distinguished by having cell walls containing ferulic acid. The commelinids are the only clade that the APG IV ...
by order of branching, from early to late. In the following cladogram numbers indicate crown group (most recent common ancestor of the sampled species of the clade of interest) divergence times in mya (unit), mya (million years ago). Of some 70,000 species, by far the largest number (65%) are found in two Family (biology), families, the orchids and grasses. The orchids (
Orchidaceae Orchidaceae ( ), common name, commonly called the orchid family, is a diverse and widespread family (biology), family of flowering plants, with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two la ...

Orchidaceae
,
Asparagales Asparagales (asparagoid lilies) is an order (biology), order of plants in modern classification systems such as the Angiosperm Phylogeny Group (APG) and the Angiosperm Phylogeny Web. The order takes its name from the type (biology), type family ...
) contain about 25,000 species and the grasses (
Poaceae Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain ...
,
Poales The Poales are a large order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or wa ...
) about 11,000. Other well known groups within the Poales Order (biology), order include the
Cyperaceae The Cyperaceae are a family of graminoid (grass-like), monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank higher than tha ...
(sedges) and
Juncaceae Juncaceae is a family of flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embryophyte, land plants, with 64 Order(biology), orders, 416 Family (biology), families, approxim ...
(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 (biology), order Arecales. Their growth form can be climbing palm, climbers, shrubs, tree-like and stemless plants, a ...

Arecaceae
, Arecales) and lilies (Liliaceae,
Liliales Liliales is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and ...
).


Evolution

In phyletic, 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 Eichler system, system of Eichler 1875–1878 onwards) the predominant theory of monocot origins was the ranalean (ranalian) theory, particularly in the work of Charles Bessey, 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 group arising early in the history of the
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s, but the fossil record is meagre. The earliest fossils presumed to be monocot remains date from the Cretaceous, early Cretaceous period. For a very long time, fossils of palm trees were believed to be the oldest monocots, first appearing 90 million years ago (mya (unit), 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–Aptian – Early Cretaceous period, about 120-110 million years ago, and are assignable to clade-Pothoideae-Monstereae Araceae; being Araceae, sister to other
Alismatales The Alismatales (alismatids) are an order of flowering plants including about 4500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Description The Alismatales comprise ...
. They have also found flower fossils of Triuridaceae (Pandanales) in Upper Cretaceous rocks in New Jersey, becoming the oldest known sighting of saprophytic/ mycotrophic habits in angiosperm plants and among the oldest known fossils of monocotyledons. Topology of the angiosperm phylogenetic tree could infer that the monocots would be 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 RuBisCO large subunit, rbcL sequences and the Network science, mean path length method for estimating genetic divergence, 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 Robust statistics, 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, which was set to 84 Ma, in the late Santonian 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 emergence of the monocots as far back as 150 mya in the Jurassic period.


Core group

The age of the core group of so-called 'nuclear monocots' or 'core monocots', which correspond to all orders except
Acorales ''Acorus'' is a genus of monocot flowering plants. This genus was once placed within the family Araceae (aroids), but more recent classifications place it in its own family Acoraceae and order Acorales, of which it is the sole genus of the oldes ...
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 The Dioscoreales are an order of monocotyledon Monocotyledons (), commonly referred to as monocots, (Lilianae Lilianae (also known as Liliiflorae) is a botanical name for a superorder (that is, a rank higher than that of order) of floweri ...
+ Pandanales and
Liliales Liliales is an order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and ...
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, 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. 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 morphology (biology), morphological autapomorphy, 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 of living in the water), roots in groups instead of a single root branching (related to the nature of the substrata (gardening), substrate), including sympodial 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 petiole (botany), 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'' (Liliales), ''Dioscorea'' (Dioscoreales), etc. A number of these plants are vines that tend to live in shaded habitats for at least part of their lives, and this fact may also relate to their shapeless stomata. 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, which refers to the fact that most members of this group have one
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germination, germinating see ...
, or embryonic leaf, in their
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positi ...

seed
s.


Ecology


Emergence

Some monocots, such as grasses, have hypogeal germination, 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 germination, 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 Red List describes four species as extinct, four as extinct in the wild, 626 as possibly extinct, 423 as critically endangered, 632 endangered, 621 vulnerable species, vulnerable, and 269 near threatened 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 any Poaceae, grass cultivated (grown) for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, cereal germ, germ, and bran. The term may also refer to the resulting grain ...

cereal
grains A grain is a small, hard, dry seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double albu ...
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 plant or animal material used as fuel to produce electricity Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position ...

biomass
produced.


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 Monocots, Plant unranked clades Early Cretaceous plants Extant Early Cretaceous first appearances