Monocotyledons ( / ˌ m ɒ n ə ˌ k ɒ t ə ˈ l iː d ə n z / ), commonly referred to as monocots , ( Lilianae sensu Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon . They constitute one of the major groups into which the flowering plants have traditionally been divided; the rest of the flowering plants have two cotyledons and were classified as dicotyledons , or dicots.
83-432: See text . The Andropogoneae , sometimes called the sorghum tribe , are a large tribe of grasses (family Poaceae ) with roughly 1,200 species in 90 genera, mainly distributed in tropical and subtropical areas. They include such important crops as maize (corn), sugarcane , and sorghum . All species in this tribe use C 4 carbon fixation , which makes them competitive under warm, high-light conditions. Andropogoneae
166-444: A phylogenetic tree to be constructed for the flowering plants. The establishment of major new clades 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
249-499: A sod -forming perennial grass used in agriculture is Thinopyrum intermedium . Grasses are used as raw material for a multitude of purposes, including construction and in the composition of building materials such as cob , for insulation, in the manufacture of paper and board such as oriented structural straw board . Grass fiber can be used for making paper , biofuel production, nonwoven fabrics, and as replacement for glass fibers used in reinforced plastics. Bamboo scaffolding
332-719: 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). Although Linnaeus (1707–1778) did not utilise Ray's discovery, basing his own classification solely on floral reproductive morphology ,
415-855: 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 of the ancestral monocotyledons, whose adaptive advantages are poorly understood, but may have been related to adaption to aquatic habitats , prior to radiation 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 are rare. Thus monocots are distinguishable from other angiosperms both in terms of their uniformity and diversity. On
498-474: A group, but with various taxonomic ranks and under several different names. The APG III system of 2009 recognises a clade called "monocots" but does not assign it to a taxonomic rank. The monocotyledons include about 70,000 species, about a quarter of all angiosperms. The largest family in this group (and in the flowering plants as a whole) by number of species are the orchids (family Orchidaceae ), with more than 20,000 species. About 12,000 species belong to
581-573: 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. Monocot apomorphies (characteristics derived during radiation rather than inherited from an ancestral form) include herbaceous habit, leaves with parallel venation and sheathed base, an embryo with
664-584: A photosynthetic pathway, linked to specialized Kranz leaf anatomy , which allows for increased water use efficiency , rendering them better adapted to hot, arid environments. The C3 grasses are referred to as "cool-season" grasses, while the C4 plants are considered "warm-season" grasses. Although the C4 species are all in the PACMAD clade (see diagram below), it seems that various forms of C4 have arisen some twenty or more times, in various subfamilies or genera. In
747-483: 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
830-582: 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
913-617: A similar position as a major division of the flowering plants throughout the nineteenth century, with minor variations. George Bentham 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
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#1732800906282996-425: A single cotyledon, an atactostele , numerous adventitious roots, sympodial 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 . The distinctive features of the monocots have contributed to the relative taxonomic stability of
1079-401: 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 structure in the 17th century. Ray, who is often considered the first botanical systematist , observed
1162-596: A smaller part of the vegetation in almost every other terrestrial habitat. Grass-dominated biomes are called grasslands. If only large, contiguous areas of grasslands are counted, these biomes cover 31% of the planet's land. Grasslands include pampas , steppes , and prairies . Grasses provide food to many grazing mammals, as well as to many species of butterflies and moths . Many types of animals eat grass as their main source of food, and are called graminivores – these include cattle , sheep , horses , rabbits and many invertebrates , such as grasshoppers and
1245-686: 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: 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
1328-509: 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 orchids (Asparagales) and bromeliads (Poales) to submarine Alismatales (including the reduced Lemnoideae ) and mycotrophic Burmanniaceae (Dioscreales) and Triuridaceae (Pandanales). Other forms of adaptation include
1411-910: A variety that include grasses that are related to modern rice and bamboo . Grasses have adapted to conditions in lush rain forests , dry deserts , cold mountains and even intertidal habitats , and are currently the most widespread plant type; grass is a valuable source of food and energy for all sorts of wildlife. A cladogram shows subfamilies and approximate species numbers in brackets: Chloridoideae (1600) Danthonioideae (300) Micrairoideae (200) Arundinoideae (50) Panicoideae (3250) Aristidoideae (350) Oryzoideae (110) Bambusoideae – bamboos (1450) Pooideae (3850) Puelioideae (11) Pharoideae (13) Anomochlooideae (4) Before 2005, fossil findings indicated that grasses evolved around 55 million years ago. Finds of grass-like phytoliths in Cretaceous dinosaur coprolites from
1494-420: Is a stub . You can help Misplaced Pages by expanding it . Poaceae Gramineae Juss. Poaceae ( / p oʊ ˈ eɪ s i . iː , - s i aɪ / poh- AY -see-e(y)e ), also called Gramineae ( / ɡ r ə ˈ m ɪ n i . iː , - n i aɪ / grə- MIN -ee-e(y)e ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses . It includes
1577-466: 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
1660-473: Is a grass used as a culinary herb for its citrus-like flavor and scent. Many species of grass are grown as pasture for foraging or as fodder for prescribed livestock feeds, particularly in the case of cattle , horses , and sheep . Such grasses may be cut and stored for later feeding, especially for the winter, in the form of bales of hay or straw , or in silos as silage . Straw (and sometimes hay) may also be used as bedding for animals. An example of
1743-570: Is able to withstand typhoon-force winds that would break steel scaffolding. Larger bamboos and Arundo donax have stout culms that can be used in a manner similar to timber, Arundo is used to make reeds for woodwind instruments , and bamboo is used for innumerable implements. Phragmites australis (common reed) is important for thatching and wall construction of homes in Africa. Grasses are used in water treatment systems, in wetland conservation and land reclamation , and used to lessen
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#17328009062821826-474: Is classified in supertribe Andropogonodae, together with its sister group Arundinelleae . Subdivisions include 12 subtribes, but the position of several genera within them is still unresolved ( incertae sedis ). Hybridisation was probably important in the evolution of the Andropogoneae, and the tribe's systematics are still not completely resolved. From the morphological point of view, the merging of
1909-986: Is for piecing together historical landscapes and weather patterns, considering other factors such as genetic material amount might also affect pollen size. Despite these challenges, new techniques in Fourier-Transform Infrared Spectroscopy (FT-IR) and improved statistical methods are now helping to better identify these similar-looking pollen types. Grasses are the primary plants used in lawns, which themselves derive from grazed grasslands in Europe. They also provide an important means of erosion control (e.g., along roadsides), especially on sloping land. Grass lawns are an important covering of playing surfaces in many sports, including football (soccer) , American football , tennis , golf , cricket , softball and baseball . Monocotyledon Monocotyledons have almost always been recognized as
1992-606: Is linked to crop improvement, since meiotic recombination is an important component of plant breeding . Unlike in animals, the specification of both male and female plant germlines occurs late in development during flowering. The transition from the sporophyte phase to the gametophyte state is initiated by meiotic entry. Grasses are, in human terms, perhaps the most economically important plant family. Their economic importance stems from several areas, including food production, industry, and lawns . They have been grown as food for domesticated animals for up to 6,000 years and
2075-499: 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 (ANA grade) with three lineages and a larger late branching grade, the core angiosperms (mesangiosperms) with five lineages, as shown in
2158-759: Is their growth pattern, lacking a lateral meristem ( cambium ) 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 , 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
2241-683: 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 . 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
2324-721: Is whose pulp is divided into two lobes and a radicle... 2. Such which neither spring out of the ground with seed leaves nor have their pulp divided into lobes John Ray (1674), pp. 164, 166 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
2407-454: The Aristida genus for example, one species ( A. longifolia ) is C3 but the approximately 300 other species are C4. As another example, the whole tribe of Andropogoneae , which includes maize , sorghum , sugar cane , " Job's tears ", and bluestem grasses , is C4. Around 46 percent of grass species are C4 plants. The name Poaceae was given by John Hendley Barnhart in 1895, based on
2490-775: The Albian stage of the Early Cretaceous approximately 113–100 million years ago, which were found to belong to primitive lineages within Poaceae, similar in position to the Anomochlooideae. These are currently the oldest known grass fossils. The relationships among the three subfamilies Bambusoideae, Oryzoideae and Pooideae in the BOP clade have been resolved: Bambusoideae and Pooideae are more closely related to each other than to Oryzoideae. This separation occurred within
2573-508: The Americas ). Sugarcane is the major source of sugar production. Additional food uses of sugarcane include sprouted grain , shoots , and rhizomes , and in drink they include sugarcane juice and plant milk , as well as rum , beer , whisky , and vodka . Bamboo shoots are used in numerous Asian dishes and broths, and are available in supermarkets in various sliced forms, in both fresh, fermented and canned versions. Lemongrass
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2656-458: The Cenozoic contributed to the spread of grasses. Without large grazers, fire-cleared areas are quickly colonized by grasses, and with enough rain, tree seedlings. Trees eventually outcompete most grasses. Trampling grazers kill seedling trees but not grasses. Sexual reproduction and meiosis have been studied in rice , maize , wheat and barley . Meiosis research in these crop species
2739-593: 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 (an orchid), and the Dioscoreales (yams). Potamogeton and Paris quadrifolia (herb-paris) are examples of monocots with tetramerous flowers. Other plants exhibit
2822-848: The cereal grasses, bamboos , the grasses of natural grassland and species cultivated in lawns and pasture . The latter are commonly referred to collectively as grass . With around 780 genera and around 12,000 species, the Poaceae is the fifth-largest plant family , following the Asteraceae , Orchidaceae , Fabaceae and Rubiaceae . The Poaceae are the most economically important plant family, providing staple foods from domesticated cereal crops such as maize , wheat , rice , oats , barley , and millet for people and as feed for meat-producing animals . They provide, through direct human consumption, just over one-half (51%) of all dietary energy; rice provides 20%, wheat supplies 20%, maize (corn) 5.5%, and other grains 6%. Some members of
2905-450: The cladogram . Amborellales Nymphaeales Austrobaileyales magnoliids Chloranthales monocots Ceratophyllales eudicots 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
2988-537: The dichotomy of cotyledon 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". The greatest number of plants that come of seed spring at first out of the earth with two leaves which being for the most part of a different figure from the succeeding leaves are by our gardeners not improperly called
3071-440: 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 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
3154-422: The ligule lies at the junction between sheath and blade, preventing water or insects from penetrating into the sheath. Flowers of Poaceae are characteristically arranged in spikelets , each having one or more florets. The spikelets are further grouped into panicles or spikes . The part of the spikelet that bears the florets is called the rachilla. A spikelet consists of two (or sometimes fewer) bracts at
3237-530: The lilioid monocots ; major cereal grains ( maize , rice , barley , rye , oats , millet , sorghum and wheat ) in the grass family ; and forage grasses ( Poales ) as well as woody tree-like palm trees ( Arecales ), bamboo , reeds and bromeliads (Poales), bananas and ginger ( Zingiberales ) in the commelinid monocots , as well as both emergent (Poales, Acorales ) and aroids , as well as floating or submerged aquatic plants such as seagrass ( Alismatales ). The most important distinction
3320-418: 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
3403-471: 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 APG system does not assign the monocots to a taxonomic rank, instead recognizing a monocots clade. However, there has remained some uncertainty regarding
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3486-562: The Poaceae are used as building materials ( bamboo , thatch , and straw ); others can provide a source of biofuel , primarily via the conversion of maize to ethanol . Grasses have stems that are hollow except at the nodes and narrow alternate leaves borne in two ranks. The lower part of each leaf encloses the stem, forming a leaf-sheath. The leaf grows from the base of the blade, an adaptation allowing it to cope with frequent grazing. Grasslands such as savannah and prairie where grasses are dominant are estimated to constitute 40.5% of
3569-733: The ability to increase the width of a stem ( secondary growth ) 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 ), screwpines ( Pandanaceae ), bananas ( Musaceae ), Yucca , Aloe , Dracaena , and Cordyline . The monocots form one of five major lineages of mesangiosperms (core angiosperms), which in themselves form 99.95% of all angiosperms . The monocots and
3652-462: 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
3735-442: The base, called glumes , followed by one or more florets. A floret consists of the flower surrounded by two bracts, one external—the lemma —and one internal—the palea . The flowers are usually hermaphroditic — maize being an important exception—and mainly anemophilous or wind-pollinated, although insects occasionally play a role. The perianth is reduced to two scales, called lodicules , that expand and contract to spread
3818-450: The caterpillars of many brown butterflies . Grasses are also eaten by omnivorous or even occasionally by primarily carnivorous animals. Grasses dominate certain biomes , especially temperate grasslands , because many species are adapted to grazing and fire. Grasses are unusual in that the meristem is near the bottom of the plant; hence, grasses can quickly recover from cropping at the top. The evolution of large grazing animals in
3901-421: The climbing vines of Araceae (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 , have adopted a therophyte life form . The cotyledon, the primordial Angiosperm leaf consists of
3984-484: 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 to develop
4067-404: The dominant members of many plant communities. The monocots are one of the major divisions of the flowering plants 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 . He observed that the majority had broad leaves with net-like venation, but
4150-835: The erosional impact of urban storm water runoff. Pollen morphology, particularly in the Poaceae family, is key to figuring out their evolutionary relationships and how environments have changed over time . Grass pollen grains, however, often look the same, making it hard to use them for detailed climate or environmental reconstructions. Grass pollen has a single pore and can vary a lot in size, from about 20 to over 100 micrometers, and this size difference has been looked into for clues about past habitats, to tell apart domesticated grasses from wild ones, and to indicate various biological features like how they perform photosynthesis , their breeding systems, and genetic complexity. Yet, there's ongoing debate about how effective pollen size
4233-419: 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 and the commelinid monocots 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
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#17328009062824316-474: The fertile, unstalked spikelet as an extension of the lemma . Classification following Soreng et al. (2017): Classification following Welker et al. (2020) (one asterisk * marks genera not sampled in their analyses that were tentatively placed based on previously published phylogenetic analyses; two asterisks ** marks genera placed solely on morphology): Tribe Andropogoneae Dumort. – 14 subtribes, 92 genera, and about 1224 species This Panicoideae article
4399-516: The former subtribe 'Dimeriinae' (having solitary spikelets borne in 'robust' raceme rachis ) into the subtribe Ischaeminae (having paired spikelets borne in 'fragile' raceme rachis) is doubtful. Affinities within the tribe are complex and still under investigation. Mr. Shahid Nawaz , a grass specialist at the Blatter Herbarium , is working on the phylogenomics of the tribe from India. According to preliminary phytogeographic research on
4482-469: The full list of Poaceae genera . The grass family is one of the most widely distributed and abundant groups of plants on Earth . Grasses are found on every continent, including Antarctica . The Antarctic hair grass, Deschampsia antarctica is one of only two plant species native to the western Antarctic Peninsula . Grasses are the dominant vegetation in many habitats, including grassland , salt-marsh , reedswamp and steppes . They also occur as
4565-478: The grains of grasses such as wheat , rice, maize (corn) and barley have been the most important human food crops . Grasses are also used in the manufacture of thatch , paper , fuel , clothing , insulation , timber for fencing , furniture , scaffolding and construction materials, floor matting , sports turf and baskets . Of all crops grown, 70% are grasses. Agricultural grasses grown for their edible seeds are called cereals or grains (although
4648-423: The group. Douglas E. Soltis and others identify thirteen synapomorphies (shared characteristics that unite monophyletic groups of taxa); 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 and do not have
4731-452: The highest species diversity and endemicity found in genera like Arthraxon , Chrysopogon , Cymbopogon , Dichanthium , Dimeria , Heteropogon , Ischaemum , Ophiorus , Sehima , and Themeda . Spikelets within the inflorescence (flower cluster) are generally arranged on spicate racemes in pairs. A fertile, unstalked spikelet is subtended by a sterile, stalked spikelet. In species where awns are present they are found on
4814-463: The land area of the Earth , excluding Greenland and Antarctica . Grasses are also an important part of the vegetation in many other habitats, including wetlands , forests and tundra . Though they are commonly called "grasses", groups such as the seagrasses , rushes and sedges fall outside this family. The rushes and sedges are related to the Poaceae, being members of the order Poales , but
4897-453: The latest Cretaceous ( Maastrichtian ) aged Lameta Formation of India have pushed this date back to 66 million years ago. In 2011, fossils from the same deposit were found to belong to the modern rice tribe Oryzeae , suggesting substantial diversification of major lineages by this time. In 2018, a study described grass microfossils extracted from the teeth of the hadrosauroid dinosaur Equijubus normani from northern China, dating to
4980-624: The latter term, when used agriculturally, refers to both cereals and similar seeds of other plant species, such as buckwheat and legumes ). Three cereals—rice, wheat, and maize (corn)—provide more than half of all calories consumed by humans. Cereals constitute the major source of carbohydrates for humans and perhaps the major source of protein; these include rice (in southern and eastern Asia ), maize (in Central and South America ), and wheat and barley (in Europe , northern Asia and
5063-464: 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). The lack of cambium in the primary root limits its ability to grow sufficiently to maintain
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#17328009062825146-463: The leaves are attached. Grass leaves are nearly always alternate and distichous (in one plane), and have parallel veins. Each leaf is differentiated into a lower sheath hugging the stem and a blade with entire (i.e., smooth) margins. The leaf blades of many grasses are hardened with silica phytoliths , which discourage grazing animals; some, such as sword grass , are sharp enough to cut human skin. A membranous appendage or fringe of hairs called
5229-469: The lemma and palea; these are generally interpreted to be modified sepals. The fruit of grasses is a caryopsis , in which the seed coat is fused to the fruit wall. A tiller is a leafy shoot other than the first shoot produced from the seed. Grass blades grow at the base of the blade and not from elongated stem tips. This low growth point evolved in response to grazing animals and allows grasses to be grazed or mown regularly without severe damage to
5312-419: 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 and Asparagales , now recognised as quite separate. A major advance in this respect
5395-411: The name implies, a single (mono-) cotyledon , or embryonic leaf, in their seeds . Historically, this feature was used to contrast the monocots with the dicotyledons 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
5478-400: The one hand that the monocots remained as a well defined 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
5561-520: The one hand, the organization 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 includes perennial geophytes such as ornamental flowers including orchids ( Asparagales ); tulips and lilies ( Liliales ); rosette and succulent epiphytes (Asparagales); mycoheterotrophs (Liliales, Dioscoreales , Pandanales ), all in
5644-400: The plant. Three general classifications of growth habit present in grasses: bunch-type (also called caespitose), stoloniferous , and rhizomatous . The success of the grasses lies in part in their morphology and growth processes and in part in their physiological diversity. There are both C3 and C4 grasses, referring to the photosynthetic pathway for carbon fixation. The C4 grasses have
5727-511: The plant. This necessitates early development of roots derived from the shoot (adventitious roots). In addition to roots, monocots develop 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 (Tillich, Figure 11). Other geophytes develop bulbs ,
5810-535: 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. The embryo consists of a single cotyledon, usually with two vascular bundles . The traditionally listed differences between monocots and dicots are as follows. This
5893-629: The relatively short time span of about 4 million years. According to Lester Charles King , the spread of grasses in the Late Cenozoic would have changed patterns of hillslope evolution favouring slopes that are convex upslope and concave downslope and lacking a free face were common. King argued that this was the result of more slowly acting surface wash caused by carpets of grass which in turn would have resulted in relatively more soil creep . There are about 12,000 grass species in about 771 genera that are classified into 12 subfamilies. See
5976-482: The same structures had introduced the term cotyledon, which Ray adopted in his subsequent writing. Mense quoque Maii, alias seminales plantulas Fabarum, & Phaseolorum, ablatis pariter binis seminalibus foliis, seu cotyledonibus, incubandas posui In the month of May, also, I incubated two seed plants, Faba and Phaseolus , after removing the two seed leaves, or cotyledons Marcello Malpighi (1679), p. 18 In this experiment, Malpighi also showed that
6059-412: The seagrasses are members of the order Alismatales . However, all of them belong to the monocot group of plants. Grasses may be annual or perennial herbs , generally with the following characteristics (the image gallery can be used for reference): The stems of grasses, called culms , are usually cylindrical (more rarely flattened, but not 3-angled) and are hollow, plugged at the nodes , where
6142-425: The seed leaves... In the first kind the seed leaves are nothing but the two lobes of the seed having their plain sides clapt together like the two halves of a walnut and therefore are of the just figure of the seed slit in sunder flat wise... Of seeds that spring out of the earth with leaves like the succeeding and no seed leaves I have observed two sorts. 1. Such as are congenerous to the first kind precedent that
6225-400: 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
6308-445: The soil, these are geophilous shoots (Tillich, Figure 11) that help overcome the limited trunk stability of large woody monocots. In nearly all cases the perigone consists of two alternating trimerous whorls of tepals , 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)
6391-403: 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 . 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
6474-490: 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 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
6557-466: The tribe Poeae described in 1814 by Robert Brown , and the type genus Poa described in 1753 by Carl Linnaeus . The term is derived from the Ancient Greek πόα (póa, "fodder") . Grasses include some of the most versatile plant life-forms . They became widespread toward the end of the Cretaceous period, and fossilized dinosaur dung ( coprolites ) have been found containing phytoliths of
6640-439: The tribe by MS Kiran Raj , Peninsular India , home to 54 genera (incl. 9 endemic genera, viz ., Bhidea , Lophopogon , Glyphochloa , Pogonachne , Trilobachne , Pseudodichanthium , Triplopogon , Nanooravia , and Manisuris ) and roughly 500 species, is thought to be the primary or secondary centre of diversity for Andropogonoid grasses. About 40% of the representative taxa are exclusively endemic to peninsular India, with
6723-458: The true grasses ( Poaceae ), which are economically the most important family of monocotyledons. Often mistaken for grasses, sedges are also monocots. In agriculture the majority of the biomass produced comes from monocotyledons. These include not only major grains ( rice , wheat , maize , etc.), but also forage grasses, sugar cane , the bamboos , and many other common food and decorative crops. The monocots or monocotyledons have, as
6806-559: 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
6889-468: 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 ). Monocotyledons remained in
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