Flowering plants are
plants that bear flowers and fruits, and form the clade Angiospermae (),
commonly called angiosperms. The term "angiosperm" is derived from the
Greek words ('container, vessel') and ('seed'), and refers to those plants that produce their
seeds enclosed within a
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...
. They are by far the most diverse group of
land plants
The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as siste ...
with 64
orders
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
, 416
families, approximately 13,000 known
genera and 300,000 known
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
.
Angiosperms were formerly called Magnoliophyta ().
Like
gymnosperm
The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...
s, angiosperms are
seed-producing plants. They are distinguished from gymnosperms by characteristics including
flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...
s,
endosperm within their seeds, and the production of fruits that contain the seeds.
The ancestors of flowering plants diverged from the common ancestor of all living gymnosperms before the end of the
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...
, over 300 million years ago. The closest fossil relatives of flowering plants are uncertain and contentious.
The earliest angiosperm fossils are in the form of pollen around 134 million years ago during the
Early Cretaceous. Over the course of the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
, angiosperms
explosively diversified, becoming the dominant group of plants across the planet by the end of the period, corresponding with the decline and extinction of previously widespread gymnosperm groups. The origin and diversification of the angiosperms is often known as "Darwin's abominable mystery".
Description
Angiosperm derived characteristics
Angiosperms differ from other
seed plants in several ways, described in the table below. These distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants, and the most commercially important group to humans.
Vascular anatomy
Angiosperm stems are made up of seven layers as shown on the right. The amount and
complexity of tissue-formation in flowering plants exceeds that of gymnosperms.
In the
dicotyledons, the
vascular bundles of the stem are arranged such that the
xylem and
phloem form concentric rings. The bundles in the very young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of
meristem or active formative tissue known as
cambium. By the formation of a layer of
cambium between the bundles (interfascicular cambium), a complete ring is formed, and a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside. The soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each
season
A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and ...
of growth, called
annual rings
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmo ...
.
Among the
monocotyledon
Monocotyledons (), 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 ...
s, the bundles are more numerous in the young stem and are scattered through the ground tissue. They contain no cambium and once formed the stem increases in diameter only in exceptional cases.
Reproductive anatomy
The characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, and provide the most trustworthy external characteristics for establishing relationships among angiosperm species. The function of the flower is to ensure
fertilization
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Pro ...
of the
ovule
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...
and development of
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in partic ...
containing
seed
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...
s. The floral apparatus may arise terminally on a shoot or from the
axil
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...
of a leaf (where the
petiole attaches to the stem). Occasionally, as in
violets, a flower arises singly in the axil of an ordinary foliage-leaf. More typically, the flower-bearing portion of the plant is sharply distinguished from the foliage-bearing or vegetative portion, and forms a more or less elaborate branch-system called an
inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are forme ...
.
There are two kinds of reproductive cells produced by flowers.
Microspores, which will divide to become
pollen grains, are the "male" cells and are borne in the
stamen
The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10
Morphology and terminology
A stamen typically consists of a stalk called the fila ...
s (or microsporophylls).
The "female" cells called
megaspores, which will divide to become the egg cell (
megagametogenesis Megagametogenesis is the process of maturation of the female gametophyte, or megagametophyte, in plants During the process of megagametogenesis, the megaspore, which arises from megasporogenesis, develops into the embryo sac, which is where the fema ...
), are contained in the
ovule
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...
and enclosed in the
carpel (or megasporophyll).
The flower may consist only of these parts, as in
willow, where each flower comprises only a few
stamen
The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10
Morphology and terminology
A stamen typically consists of a stalk called the fila ...
s or two carpels. Usually, other structures are present and serve to protect the
sporophylls and to form an envelope attractive to pollinators. The individual members of these surrounding structures are known as
sepal
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coine ...
s and
petals (or
tepals in flowers such as ''
Magnolia
''Magnolia'' is a large genus of about 210 to 340The number of species in the genus ''Magnolia'' depends on the taxonomic view that one takes up. Recent molecular and morphological research shows that former genera ''Talauma'', ''Dugandiodendr ...
'' where sepals and petals are not distinguishable from each other). The outer series (calyx of sepals) is usually green and leaf-like, and functions to protect the rest of the flower, especially the bud. The inner series (corolla of petals) is, in general, white or brightly colored, and is more delicate in structure. It functions to attract
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
or
bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
pollinators. Attraction is effected by color,
scent, and
nectar, which may be secreted in some part of the flower. The characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans.
While the majority of flowers are perfect or
hermaphrodite (having both pollen and ovule producing parts in the same flower structure), flowering plants have developed numerous morphological and
physiological mechanisms to reduce or prevent self-fertilization. Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal
pollinators cannot easily transfer pollen to the pistil (receptive part of the carpel). Homomorphic flowers may employ a biochemical (physiological) mechanism called
self-incompatibility to discriminate between self and non-self pollen grains. Alternatively, in
dioecious species, the male and female parts are morphologically separated, developing on different individual flowers.
Taxonomy
History of classification
The botanical term "angiosperm", from Greek words ( 'bottle, vessel') and ( 'seed'), was coined in the form "Angiospermae" by
Paul Hermann in 1690 but he used this term to refer to a group of plants which form only a subset of what today are known as angiosperms. Hermannn's Angiospermae including only flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, which were flowering plants with
achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked. The terms Angiospermae and Gymnospermae were used by
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, ...
with the same sense, but with restricted application, in the names of the orders of his class Didynamia.
The terms angiosperms and gymnosperm fundamentally changed in meaning in 1827 when
Robert Brown established the existence of truly naked ovules in the
Cycadeae and
Coniferae. The term gymnosperm was from then on applied to seed plants with naked ovules, and the term angiosperm to seed plants with enclosed ovules. However, for many years after Brown's discovery, the primary division of the seed plants was seen as between monocots and dicots, with gymnosperms as a small subset of the dicots.
In 1851,
Hofmeister discovered the changes occurring in the embryo-sac of flowering plants, and determined the correct relationships of these to the
Cryptogamia. This fixed the position of Gymnosperms as a class distinct from Dicotyledons, and the term Angiosperm then gradually came to be accepted as the suitable designation for the whole of the flowering plants other than Gymnosperms, including the classes of Dicotyledons and Monocotyledons.
This is the sense in which the term is used today.
In most taxonomies, the flowering plants are treated as a coherent group. The most popular descriptive name has been Angiospermae, with
Anthophyta
The anthophytes are a grouping of plant taxa bearing flower-like reproductive structures. They were formerly thought to be a clade comprising plants bearing flower-like structures. The group contained the angiosperms - the extant flowering plant ...
(lit. 'flower-plants') a second choice (both unranked). The
Wettstein system and
Engler system treated them as a subdivision (Angiospermae). The
Reveal system also treated them as a subdivision (Magnoliophytina), but later split it to Magnoliopsida, Liliopsida, and Rosopsida. The
Takhtajan system and
Cronquist system treat them as a division (Magnoliophyta). The
Dahlgren system and
Thorne system (1992) treat them as a class (Magnoliopsida). The
APG system of 1998, and the later 2003 and 2009 revisions, treat the flowering plants as an unranked clade without a formal Latin name (angiosperms). A formal classification was published alongside the 2009 revision in which the flowering plants rank as a subclass (Magnoliidae).
The internal classification of this group has undergone considerable revision. The
Cronquist system, proposed by
Arthur Cronquist in 1968 and published in its full form in 1981, is still widely used but is no longer believed to accurately reflect
phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological s ...
. A consensus about how the flowering plants should be arranged has recently begun to emerge through the work of the
Angiosperm Phylogeny Group (APG), which published an influential reclassification of the angiosperms in 1998. Updates incorporating more recent research were published as the
APG II system in 2003, the
APG III system in 2009, and the
APG IV system
The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was published ...
in 2016.
Traditionally, the flowering plants are divided into two groups,
*
Dicotyledoneae
The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...
or
Magnoliopsida
*
Monocotyledoneae or
Liliopsida
to which the Cronquist system ascribes the classes Magnoliopsida (from "
Magnoliaceae") and Liliopsida (from "
Liliaceae
The lily family, Liliaceae, consists of about 15 genera and 610 species of flowering plants within the order Liliales. They are monocotyledonous, perennial, herbaceous, often bulbous geophytes. Plants in this family have evolved with a fair ...
"). Other descriptive names allowed by Article 16 of the
ICBN include Dicotyledones or Dicotyledoneae, and Monocotyledones or Monocotyledoneae, which have a long history of use. In plain English, their members may be called "dicotyledons" ("dicots") and "monocotyledons" ("monocots"). The Latin behind these names refers the observation that the dicots most often have two
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 germinating seed." The numb ...
s, or embryonic leaves, within each seed. The monocots usually have only one, but the rule is not absolute either way. From a broad diagnostic point of view, the number of cotyledons is neither a particularly handy, nor a reliable character.
Recent studies, as by the APG, show that the monocots form a
monophyletic group (a
clade) but that the dicots are
paraphyletic. Nevertheless, the majority of dicot species fall into a clade, the
eudicots
The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons.
Traditionally they were called tricolpates or non-magnoliid dicot ...
or
tricolpates
The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons.
Traditionally they were called tricolpates or non-magnoliid dicot ...
, and most of the remaining fall into another major clade, the
magnoliids
Magnoliids (or Magnoliidae or Magnolianae) are a clade of flowering plants. With more than 10,000 species, including magnolias, nutmeg, bay laurel, cinnamon, avocado, black pepper, tulip tree and many others, it is the third-largest group of a ...
, containing about 9,000 species. The rest include a paraphyletic grouping of early branching taxa known collectively as the
basal angiosperms, plus the families
Ceratophyllaceae and
Chloranthaceae.
Modern classification
There are eight groups of living angiosperms:
*
Basal angiosperms (ANA: ''Amborella'', Nymphaeales, Austrobaileyales)
** ''
Amborella'', a single species of shrub from
New Caledonia;
**
Nymphaeales, about 80 species,
Figure 2
water lilies and
Hydatellaceae;
**
Austrobaileyales, about 100 species
of
woody plants from various parts of the world
*
Core angiosperms (Mesangiospermae)
**
Chloranthales
Chloranthaceae is a family of flowering plants (angiosperms), the only family in the order Chloranthales. It is not closely related to any other family of flowering plants, and is among the early-diverging lineages in the angiosperms. They ar ...
, 77 known species of aromatic plants with toothed leaves;
**
Magnoliids
Magnoliids (or Magnoliidae or Magnolianae) are a clade of flowering plants. With more than 10,000 species, including magnolias, nutmeg, bay laurel, cinnamon, avocado, black pepper, tulip tree and many others, it is the third-largest group of a ...
, about 10,000 species,
characterised by
trimerous flowers, pollen with one pore, and usually branching-veined leaves—for example
magnolia
''Magnolia'' is a large genus of about 210 to 340The number of species in the genus ''Magnolia'' depends on the taxonomic view that one takes up. Recent molecular and morphological research shows that former genera ''Talauma'', ''Dugandiodendr ...
s,
bay laurel, and
black pepper
Black pepper (''Piper nigrum'') is a flowering vine in the family Piperaceae, cultivated for its fruit, known as a peppercorn, which is usually dried and used as a spice and seasoning. The fruit is a drupe (stonefruit) which is about in dia ...
;
**
Monocots, about 70,000 species, characterised by trimerous flowers, a single
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 germinating seed." The numb ...
, pollen with one pore, and usually parallel-veined leaves—for example
grasses
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns ...
,
orchid
Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant.
Along with the Asteraceae, they are one of the two largest families of floweri ...
s, and
palms;
** ''
Ceratophyllum'', about 6 species
of
aquatic plants, perhaps most familiar as
aquarium
An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...
plants;
**
Eudicots
The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons.
Traditionally they were called tricolpates or non-magnoliid dicot ...
, about 175,000 species,
characterised by 4- or 5-merous flowers, pollen with three pores, and usually branching-veined leaves—for example
sunflower
The common sunflower (''Helianthus annuus'') is a large annual forb of the genus ''Helianthus'' grown as a crop for its edible oily seeds. Apart from cooking oil production, it is also used as livestock forage (as a meal or a silage plant), ...
s,
petunia,
buttercup
''Ranunculus'' is a large genus of about almost 1700 to more than 1800 species of flowering plants in the family Ranunculaceae. Members of the genus are known as buttercups, spearworts and water crowfoots.
The genus is distributed in Europe, ...
,
apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
s, and
oaks.
The exact relationships among these eight groups is not yet clear, although there is agreement that the first three groups to diverge from the ancestral angiosperm were
Amborellales,
Nymphaeales, and Austrobaileyales (basal angiosperms) Of the remaining five groups (core angiosperms), the relationships among the three broadest groups remains unclear (magnoliids, monocots, and eudicots). Zeng and colleagues (Fig. 1) describe four competing schemes.The eudicots and monocots are the largest and most diversified, with ~ 75% and 20% of angiosperm species, respectively. Some analyses make the magnoliids the first to diverge, others the monocots. ''Ceratophyllum'' seems to group with the eudicots rather than with the monocots. The APG IV retained the overall higher order relationship described in APG III.
Evolutionary history
Paleozoic
Fossilised
spores suggest that land plants (
embryophyte
The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sis ...
s) have existed for at least 475 million years. Early land plants
reproduced sexually with flagellated, swimming sperm, like the green algae from which they evolved. An adaptation to terrestrialization was the development of upright
sporangia
A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...
for dispersal by
spores to new habitats. This feature is lacking in the descendants of their nearest algal relatives, the
Charophycean green algae. A later terrestrial adaptation took place with retention of the delicate, avascular sexual stage, the gametophyte, within the tissues of the vascular sporophyte. This occurred by spore germination within sporangia rather than spore release, as in non-seed plants. A current example of how this might have happened can be seen in the precocious spore germination in ''
Selaginella
''Selaginella'' is the sole genus of vascular plants in the family Selaginellaceae, the spikemosses or lesser clubmosses.
This family is distinguished from Lycopodiaceae (the clubmosses) by having scale-leaves bearing a ligule and by having ...
'', the spike-moss. The result for the ancestors of angiosperms and gymnosperms was enclosing the female gamete in a case, the seed.
The first seed bearing plants were gymnosperms, like the
ginkgo, and
conifers (such as
pine
A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family (biology), family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanic ...
s and
firs). These did not produce flowers. The pollen grains (male gametophytes) of ''Ginkgo'' and cycads produce a pair of flagellated, mobile sperm cells that "swim" down the developing pollen tube to the female and her eggs.
Angiosperms appear suddenly and in great diversity in the fossil record in the Early Cretaceous.
This poses such a problem for the theory of gradual
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
that
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
called it an "abominable mystery".
Several groups of extinct gymnosperms, in particular
seed ferns, have been proposed as the
ancestors
An ancestor, also known as a forefather, fore-elder or a forebear, is a parent or ( recursively) the parent of an antecedent (i.e., a grandparent, great-grandparent, great-great-grandparent and so forth). ''Ancestor'' is "any person from w ...
of flowering plants, but there is no continuous fossil evidence showing how flowers evolved, and botanists still regard it as a mystery.
Several claims of pre-Cretaceous angiosperm fossils have been made, such as the upper
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
''
Sanmiguelia lewisi'', but none of these are widely accepted by paleobotanists.
Oleanane, a
secondary metabolite produced by many flowering plants, has been found in
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...
deposits of that age together with fossils of
gigantopterid
Gigantopterids (Gigantopteridales) is an extinct, possibly polyphyletic group of plants known from the Permian period. Gigantopterids were among the most advanced land plants of the Paleozoic Era and disappeared around the Permian–Triassic ...
s. Gigantopterids are a group of extinct seed plants that share many morphological traits with flowering plants, although they are not known to have been flowering plants themselves. Molecular evidence suggests that the ancestors of angiosperms diverged from the gymnosperms during the late
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...
, about 365 million years ago, despite only appearing in the fossil record during the Early Cretaceous, almost two hundred million years later.
Triassic and Jurassic
Based on fossil evidence, some have proposed that the ancestors of the angiosperms diverged from an unknown group of gymnosperms in the Triassic period (245–202 million years ago). Fossil angiosperm-like pollen from the Middle Triassic (247.2–242.0 Ma) suggests an older date for their origin, which is further supported by genetic evidence of the ancestors of angiosperms diverging during the Devonian.
A close relationship between angiosperms and
gnetophytes, proposed on the basis of
morphological evidence, has more recently been disputed on the basis of
molecular evidence that suggest gnetophytes are instead more closely related to conifers and other gymnosperms.
The fossil plant species
''Nanjinganthus dendrostyla'' from
Early Jurassic China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
seems to share many exclusively angiosperm features, such as a thickened
receptacle with
ovule
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...
s, and thus might represent a
crown-group or a
stem-group angiosperm. However, these have been disputed by other researchers, who contend that the structures are misinterpreted decomposed conifer cones.
The evolution of seed plants and later angiosperms appears to be the result of two distinct rounds of
whole genome duplication events.
These occurred at and . Another possible whole genome duplication event at perhaps created the ancestral line that led to all modern flowering plants. That event was studied by sequencing the genome of an ancient flowering plant, ''
Amborella trichopoda
''Amborella'' is a monotypic genus of understory shrubs or small trees endemic to the main island, Grande Terre, of New Caledonia in the southwest Pacific Ocean. The genus is the only member of the family Amborellaceae and the order Ambor ...
.''
One study has suggested that the early-middle
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
plant ''
Schmeissneria'', traditionally considered a type of ginkgo, may be the earliest known angiosperm, or at least a close relative. This, along with all other pre-Cretaceous angiosperm fossil claims, is strongly disputed by many paleobotanists.
Many paleobotanists consider the
Caytoniales
The Caytoniales (Figs. 1-2) are an extinct order of seed plants known from fossils collected throughout the Mesozoic Era, around . They are regarded as seed ferns because they are seed-bearing plants with fern-like leaves. Although at one time c ...
, a group of "
seed ferns
A seed is an Plant embryogenesis, embryonic plant enclosed in a testa (botany), protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, includ ...
" that first appeared during the Triassic and went extinct in the Cretaceous, to be amongst the best candidates for a close relative of angiosperms.
Cretaceous
Whereas the earth had previously been dominated by ferns and conifers, angiosperms quickly spread during the Cretaceous. They now comprise about 90% of all plant species including most food crops. It has been proposed that the swift rise of angiosperms to dominance was facilitated by a reduction in their genome size. During the early Cretaceous period, only angiosperms underwent rapid genome downsizing, while genome sizes of ferns and gymnosperms remained unchanged. Smaller genomes—and smaller nuclei—allow for faster rates of cell division and smaller cells. Thus, species with smaller genomes can pack more, smaller cells—in particular veins and stomata—into a given leaf volume. Genome downsizing therefore facilitated higher rates of leaf gas exchange (transpiration and photosynthesis) and faster rates of growth. This would have countered some of the negative physiological effects of genome duplications, facilitated increased uptake of carbon dioxide despite concurrent declines in atmospheric CO
2 concentrations, and allowed the flowering plants to outcompete other land plants.
The oldest known fossils definitively attributable to angiosperms are reticulated monosulcate pollen from the late
Valanginian
In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretace ...
(Early or Lower Cretaceous - 140 to 133 million years ago) of Italy and Israel, likely representative of the
basal angiosperm
The basal angiosperms are the flowering plants which diverged from the lineage leading to most flowering plants. In particular, the most basal angiosperms were called the ANITA grade, which is made up of ''Amborella'' (a single species of shrub f ...
grade.
The earliest known
macrofossil confidently identified as an angiosperm, ''
Archaefructus liaoningensis'', is dated to about 125 million
years BP
Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becaus ...
(the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period), whereas pollen considered to be of angiosperm origin takes the
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
record back to about 130 million years BP,
with ''
Montsechia
''Montsechia'' is an extinct genus of aquatic plants containing the species ''Montsechia vidalii'', discovered in Spain. ''Montsechia vidalii'' lived about 130 million years ago, during the Barremian age, and appears to be the earliest known flo ...
'' representing the earliest flower at that time.
In 2013 flowers encased in amber were found and dated 100 million years before present. The amber had frozen the act of sexual reproduction in the process of taking place. Microscopic images showed tubes growing out of pollen and penetrating the flower's stigma. The pollen was sticky, suggesting it was carried by insects. In August 2017, scientists presented a detailed description and 3D model image of what the first flower possibly looked like, and presented the hypothesis that it may have lived about
140 million years ago.
A
Bayesian analysis of 52 angiosperm taxa suggested that the crown group of angiosperms evolved between and .
Recent
DNA analysis based on
molecular systematics showed that
''Amborella trichopoda'', found on the Pacific island of
New Caledonia, belongs to a
sister group of the other flowering plants, and morphological studies suggest that it has features that may have been characteristic of the earliest flowering plants. The orders
Amborellales,
Nymphaeales, and
Austrobaileyales diverged as separate lineages from the remaining angiosperm clade at a very early stage in flowering plant evolution.
The great angiosperm
radiation, when a great diversity of angiosperms appears in the fossil record, occurred in the mid-
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
(approximately 100 million years ago). However, a study in 2007 estimated that the division of the five most recent of the eight main groups occurred around 140 million years ago. (the genus ''
Ceratophyllum'', the family
Chloranthaceae, the
eudicots
The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons.
Traditionally they were called tricolpates or non-magnoliid dicot ...
, the
magnoliids
Magnoliids (or Magnoliidae or Magnolianae) are a clade of flowering plants. With more than 10,000 species, including magnolias, nutmeg, bay laurel, cinnamon, avocado, black pepper, tulip tree and many others, it is the third-largest group of a ...
, and the
monocots) .
It is generally assumed that the
function of flowers, from the start, was to involve mobile animals in their reproduction processes. That is, pollen can be scattered even if the flower is not brightly colored or oddly shaped in a way that attracts animals; however, by expending the energy required to create such traits, angiosperms can enlist the aid of animals and, thus, reproduce more efficiently.
Island genetics provides one proposed explanation for the sudden, fully developed appearance of flowering plants. Island genetics is believed to be a common source of
speciation in general, especially when it comes to radical adaptations that seem to have required inferior transitional forms. Flowering plants may have evolved in an isolated setting like an
island
An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An isla ...
or island chain, where the plants bearing them were able to develop a highly specialised relationship with some specific animal (a
wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
, for example). Such a relationship, with a hypothetical wasp carrying pollen from one plant to another much the way
fig wasps do today, could result in the development of a high degree of
specialisation in both the plant(s) and their partners. Note that the wasp example is not incidental;
bees, which, it is postulated, evolved specifically due to mutualistic plant relationships, are descended from wasps.
Animals are also involved in the distribution of seeds. Fruit, which is formed by the enlargement of flower parts, is frequently a seed-dispersal tool that attracts animals to eat or otherwise disturb it, incidentally scattering the seeds it contains (see
frugivory). Although many such
mutualistic relationships remain too fragile to survive
competition
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, ind ...
and to spread widely, flowering proved to be an unusually effective means of reproduction, spreading (whatever its origin) to become the dominant form of land plant life.
Flower
ontogeny
Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the s ...
uses a combination of
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s normally responsible for forming new shoots. The most primitive flowers probably had a variable number of flower parts, often separate from (but in contact with) each other. The flowers tended to grow in a spiral pattern, to be bisexual (in plants, this means both male and female parts on the same flower), and to be dominated by the
ovary (female part). As flowers evolved, some variations developed parts fused together, with a much more specific number and design, and with either specific sexes per flower or plant or at least "ovary-inferior". Flower evolution continues to the present day; modern flowers have been so profoundly influenced by humans that some of them cannot be pollinated in nature. Many modern domesticated flower species were formerly simple weeds, which sprouted only when the ground was disturbed. Some of them tended to grow with human crops, perhaps already having symbiotic
companion plant relationships with them, and the prettiest did not get plucked because of their beauty, developing a dependence upon and special adaptation to human affection.
A few
paleontologists have also proposed that flowering plants, or angiosperms, might have evolved due to interactions with dinosaurs. One of the idea's strongest proponents is
Robert T. Bakker. He proposes that
herbivorous dinosaurs, with their eating habits, provided a selective pressure on plants, for which adaptations either succeeded in deterring or coping with predation by herbivores.
By the late Cretaceous, angiosperms appear to have dominated environments formerly occupied by
fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...
s and
cycadophytes, but large canopy-forming trees replaced
conifers as the dominant trees only close to the end of the Cretaceous 66 million years ago or even later, at the beginning of the
Paleogene.
The radiation of herbaceous angiosperms occurred much later. Yet, many fossil plants recognisable as belonging to modern families (including
beech,
oak,
maple
''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since h ...
, and
magnolia
''Magnolia'' is a large genus of about 210 to 340The number of species in the genus ''Magnolia'' depends on the taxonomic view that one takes up. Recent molecular and morphological research shows that former genera ''Talauma'', ''Dugandiodendr ...
) had already appeared by the late Cretaceous. Flowering plants appeared in Australia about 126 million years ago. This also pushed the age of
ancient Australian vertebrates, in what was then a
south polar continent, to 126-110 million years old.
Gallery of photos
Asteracea poster 3.jpg, A poster of twelve different species of flowers of the family Asteraceae
Lupinus-pilosus-2015-Zachi-Evenor-cropped01.jpg, ''Lupinus pilosus
''Lupinus pilosus'', commonly known as blue lupine, ( he, תורמוס ההרים, ar, ترمس برّي) is a species of flowering plant from the family Fabaceae which is endemic to Israel where it is found in Mediterranean scrubland. It has a ...
''
Rose bud.jpg, Bud of a pink rose
A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...
Diversity
The number of species of flowering plants is estimated to be in the range of 250,000 to 400,000. This compares to around 12,000 species of
moss and 11,000 species of
pteridophytes,
showing that flowering plants are much more diverse. The number of
families in
APG (1998) was 462. In
APG II (2003) it is not settled; at maximum it is 457, but within this number there are 55 optional segregates, so that the minimum number of families in this system is 402. In
APG III (2009) there are 415 families.
Compared to the APG III system, the
APG IV
The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was publish ...
system recognizes five new orders (Boraginales, Dilleniales, Icacinales, Metteniusales and Vahliales), along with some new families, making a total of 64 angiosperm orders and 416 families.
[
The diversity of flowering plants is not evenly distributed. Nearly all species belong to the eudicot (75%), monocot (23%), and magnoliid (2%) clades. The remaining five clades contain a little over 250 species in total; i.e. less than 0.1% of flowering plant diversity, divided among nine families. The 43 most diverse of 443 families of flowering plants by species,] in their APG circumscriptions, are
# Asteraceae
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...
or Compositae (daisy
Daisy, Daisies or DAISY may refer to:
Plants
* ''Bellis perennis'', the common daisy, lawn daisy or English daisy, a European species
Other plants known as daisy
* Asteraceae, daisy family
** '' Euryops chrysanthemoides'', African bush daisy
** ' ...
family): 22,750 species;
# Orchidaceae
Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant.
Along with the Asteraceae, they are one of the two largest families of flowerin ...
(orchid family): 21,950;
# or Leguminosae ( bean family): 19,400;
# Rubiaceae (madder
''Rubia'' is the type genus of the Rubiaceae family of flowering plants, which also contains coffee. It contains around 80 species of perennial scrambling or climbing herbs and subshrubs native to the Old World. The genus and its best-know ...
family): 13,150;
# Poaceae or Gramineae (grass family): 10,035;
# Lamiaceae or Labiatae (mint
MiNT is Now TOS (MiNT) is a free software alternative operating system kernel for the Atari ST system and its successors. It is a multi-tasking alternative to TOS and MagiC. Together with the free system components fVDI device drivers, XaAE ...
family): 7,175;
# Euphorbiaceae (spurge
''Euphorbia'' is a very large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae. "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to t ...
family): 5,735;
# Melastomataceae or Melastomaceae ( melastome family): 5,005;
# Myrtaceae ( myrtle family): 4,625;
# Apocynaceae
Apocynaceae (from '' Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison Members ...
( dogbane family): 4,555;
# Cyperaceae ( sedge family): 4,350;
# Malvaceae
Malvaceae, or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of economic importance include okra, cotton, cacao and durian. There are also some genera containing familia ...
( mallow family): 4,225;
# Araceae ( arum family): 4,025;
# Ericaceae ( heath family): 3,995;
# Gesneriaceae
Gesneriaceae, the gesneriad family, is a family of flowering plants consisting of about 152 genera and ca. 3,540 species in the tropics and subtropics of the Old World (almost all Didymocarpoideae) and the New World (most Gesnerioideae), ...
(gesneria
''Gesneria'' is a genus of approximately 50 species in the flowering plant family Gesneriaceae. Except for two or three odd South American species, all are native to islands of the Caribbean
The Caribbean (, ) ( es, El Caribe; french: la ...
d family): 3,870;
# Apiaceae or Umbelliferae ( parsley family): 3,780;
# Brassicaceae or Cruciferae (cabbage
Cabbage, comprising several cultivars of ''Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.&n ...
family): 3,710:
# Piperaceae
The Piperaceae (), also known as the pepper family, are a large family of flowering plants. The group contains roughly 3,600 currently accepted species in 5 genera. The vast majority of species can be found within the two main genera: '' Piper' ...
( pepper family): 3,600;
# Bromeliaceae ( bromeliad family): 3,540;
# Acanthaceae ( acanthus family): 3,500;
# Rosaceae (rose
A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...
family): 2,830;
# Boraginaceae
Boraginaceae, the borage or forget-me-not family, includes about 2,000 species of shrubs, trees and herbs in 146, to 156 genera with a worldwide distribution.
The APG IV system from 2016 classifies the Boraginaceae as single family of the ...
( borage family): 2,740;
# Urticaceae (nettle family): 2,625;
# Ranunculaceae
Ranunculaceae (buttercup or crowfoot family; Latin "little frog", from "frog") is a family of over 2,000 known species of flowering plants in 43 genera, distributed worldwide.
The largest genera are ''Ranunculus'' (600 species), ''Delphinium' ...
(buttercup
''Ranunculus'' is a large genus of about almost 1700 to more than 1800 species of flowering plants in the family Ranunculaceae. Members of the genus are known as buttercups, spearworts and water crowfoots.
The genus is distributed in Europe, ...
family): 2,525;
# Lauraceae ( laurel family): 2,500;
# Solanaceae ( nightshade family): 2,460;
# Campanulaceae ( bellflower family): 2,380;
# Arecaceae ( palm family): 2,361;
# Annonaceae ( custard apple family): 2,220;
# Caryophyllaceae
Caryophyllaceae, commonly called the pink family or carnation family, is a family of flowering plants. It is included in the dicotyledon order Caryophyllales in the APG III system, alongside 33 other families, including Amaranthaceae, Cactacea ...
(pink
Pink is the color of a namesake flower that is a pale tint of red. It was first used as a color name in the late 17th century. According to surveys in Europe and the United States, pink is the color most often associated with charm, politeness, ...
family): 2,200;
# Orobanchaceae
Orobanchaceae, the broomrapes, is a family of mostly parasitic plants of the order Lamiales, with about 90 genera and more than 2000 species. Many of these genera (e.g., ''Pedicularis'', ''Rhinanthus'', '' Striga'') were formerly included in ...
(broomrape
''Orobanche'', commonly known as broomrape, is a genus of over 200 species of small parasitic herbaceous plants, mostly native to the temperate Northern Hemisphere. It is the type genus of the broomrape family Orobanchaceae.
Description
Broom ...
family): 2,060;
# Amaranthaceae
Amaranthaceae is a family of flowering plants commonly known as the amaranth family, in reference to its type genus ''Amaranthus''. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, making i ...
( amaranth family): 2,050;
# Iridaceae
Iridaceae is a family of plants in order Asparagales, taking its name from the irises, meaning rainbow, referring to its many colours. There are 66 accepted genera with a total of c. 2244 species worldwide (Christenhusz & Byng 2016). It inclu ...
( iris family): 2,025;
# Aizoaceae
The Aizoaceae, or fig-marigold family, is a large family of dicotyledonous flowering plants containing 135 genera and about 1800 species. They are commonly known as ice plants or carpet weeds. They are often called vygies in South Africa and N ...
or Ficoidaceae ( ice plant family): 2,020;
# Rutaceae ( rue family): 1,815;
# Phyllanthaceae (phyllanthus
''Phyllanthus'' is the largest genus in the plant family Phyllanthaceae. Estimates of the number of species in this genus vary widely, from 750David J. Mabberley. 2008. ''Mabberley's Plant-Book.'' third edition (2008). Cambridge University ...
family): 1,745;
# Scrophulariaceae (figwort
The genus ''Scrophularia'' of the family Scrophulariaceae comprises about 200 species of herbaceous flowering plants commonly known as figworts. Species of ''Scrophularia'' all share square stems, opposite leaves and open two-lipped flowers for ...
family): 1,700;
# Gentianaceae
Gentianaceae is a family of flowering plants of 103 genera and about 1600 species.
Etymology
The family takes its name from the genus ''Gentiana'', named after the Illyrian king Gentius.
Distribution
Distribution is cosmopolitan.
Characteristi ...
( gentian family): 1,650;
# Convolvulaceae ( bindweed family): 1,600;
# Proteaceae ( protea family): 1,600;
# Sapindaceae ( soapberry family): 1,580;
# Cactaceae
A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Gre ...
(cactus
A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Gree ...
family): 1,500;
# Araliaceae
The Araliaceae are a family of flowering plants composed of about 43 genera and around 1500 species consisting of primarily woody plants and some herbaceous plants. The morphology of Araliaceae varies widely, but it is predominantly distinguis ...
(''Aralia
''Aralia'' , or spikenard, is a genus of the family Araliaceae, consisting of 68 accepted species of deciduous or evergreen trees, shrubs, and rhizomatous herbaceous perennials. The genus is native to Asia and the Americas, with most specie ...
'' or ivy
''Hedera'', commonly called ivy (plural ivies), is a genus of 12–15 species of evergreen climbing or ground-creeping woody plants in the family Araliaceae, native to western, central and southern Europe, Macaronesia, northwestern Africa and ...
family): 1,450.
Of these, the Orchidaceae, Poaceae, Cyperaceae, Araceae, Bromeliaceae, Arecaceae, and Iridaceae are monocot families; Piperaceae, Lauraceae, and Annonaceae are magnoliid dicots; the rest of the families are eudicots.
Reproduction
Fertilisation and embryogenesis
Double fertilization refers to a process in which two sperm cells fertilise cells in the ovule. This process begins when a pollen grain adheres to the stigma of the pistil (female reproductive structure), germinates, and grows a long pollen tube. While this pollen tube is growing, a haploid generative cell travels down the tube behind the tube nucleus. The generative cell divides by mitosis to produce two haploid (''n'') sperm cells. As the pollen tube grows, it makes its way from the stigma, down the style and into the ovary. Here the pollen tube reaches the micropyle of the ovule and digests its way into one of the synergids, releasing its contents (which include the sperm cells). The synergid that the cells were released into degenerates and one sperm makes its way to fertilise the egg cell, producing a diploid (2''n'') zygote. The second sperm cell fuses with both central cell nuclei, producing a triploid (3''n'') cell. As the zygote develops into an embryo, the triploid cell develops into the endosperm, which serves as the embryo's food supply. The ovary will now develop into a fruit and the ovule will develop into a seed.
Fruit and seed
As the development of the embryo and endosperm proceeds within the embryo sac, the sac wall enlarges and combines with the nucellus
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the '' nucellus'' (or remnant of the megasporangium), and the ...
(which is likewise enlarging) and the integument to form the ''seed coat''. The ovary wall develops to form the fruit or pericarp, whose form is closely associated with type of seed dispersal system.
Frequently, the influence of fertilisation is felt beyond the ovary, and other parts of the flower take part in the formation of the fruit, e.g., the floral receptacle in the apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
, strawberry
The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The fruit is widely ap ...
, and others.
The character of the seed coat bears a definite relation to that of the fruit. They protect the embryo and aid in dissemination; they may also directly promote germination. Among plants with indehiscent fruits, in general, the fruit provides protection for the embryo and secures dissemination. In this case, the seed coat is only slightly developed. If the fruit is dehiscent and the seed is exposed, in general, the seed-coat is well developed and must discharge the functions otherwise executed by the fruit.
In some cases, like in the Asteraceae family, species have evolved to exhibit heterocarpy, or the production of different fruit morphs.[Gardocki, M. E., Zablocki, H., El-Keblawy, A., & Freeman, D. C. (2000). Heterocarpy in Calendula micrantha (Asteraceae): The effects of competition and availability of water on the performance of offspring from different fruit morphs. Evolutionary Ecology Research. 2(6):701-718] These fruit morphs, produced from one plant, are different in size and shape, which influence dispersal range and germination rate. These fruit morphs are adapted to different environments, increasing chances for survival.
Meiosis
Like all diploid multicellular organisms that use sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote th ...
, flowering plants generate gametes using a specialised type of cell division called meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately ...
. Meiosis takes place in the ovule
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...
—a structure within the ovary that is located within the pistil at the centre of the flower (see diagram labeled "Angiosperm lifecycle"). A diploid cell (megaspore mother cell
A megaspore mother cell, or megasporocyte, is a diploid cell in plants in which meiosis will occur, resulting in the production of four haploid megaspores. At least one of the spores develop into haploid female gametophytes (megagametophytes).Solom ...
) in the ovule undergoes meiosis (involving two successive cell divisions) to produce four cells (megaspores) with haploid nuclei. It is thought that the basal chromosome number in angiosperms is n = 7. One of these four cells (megaspore) then undergoes three successive mitotic divisions to produce an immature embryo sac (megagametophyte) with eight haploid nuclei. Next, these nuclei are segregated into separate cells by cytokinesis to produce three antipodal cells, two synergid cells and an egg cell. Two polar nuclei are left in the central cell of the embryo sac.
Pollen is also produced by meiosis in the male anther (microsporangium
Microsporangia are sporangia that produce microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fer ...
). During meiosis, a diploid microspore mother cell undergoes two successive meiotic divisions to produce four haploid cells (microspores or male gametes). Each of these microspores, after further mitoses, becomes a pollen grain (microgametophyte) containing two haploid generative (sperm) cells and a tube nucleus. When a pollen grain makes contact with the female stigma, the pollen grain forms a pollen tube that grows down the style into the ovary. In the act of fertilisation, a male sperm nucleus fuses with the female egg nucleus to form a diploid zygote
A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism.
In multicell ...
that can then develop into an embryo within the newly forming seed. Upon germination of the seed, a new plant can grow and mature.
The adaptive function of meiosis is currently a matter of debate. A key event during meiosis in a diploid cell is the pairing of homologous chromosomes and homologous recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
(the exchange of genetic information) between homologous chromosomes. This process promotes the production of increased genetic diversity among progeny and the recombinational repair of damages in the DNA to be passed on to progeny. To explain the adaptive function of meiosis in flowering plants, some authors emphasise diversity and others emphasise DNA repair
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA d ...
.
Apomixis
Apomixis (reproduction via asexually formed seeds) is found naturally in about 2.2% of angiosperm genera. One type of apomixis, gametophytic apomixis found in a dandelion species involves formation of an unreduced embryo sac due to incomplete meiosis (apomeiosis) and development of an embryo from the unreduced egg inside the embryo sac, without fertilisation (parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...
).
Some angiosperms, including many citrus varieties, are able to produce fruits through a type of apomixis called nucellar embryony
Nucellar embryony (notated Nu+) is a form of seed reproduction that occurs in certain plant species, including many citrus varieties. Nucellar embryony is a type of apomixis, where eventually nucellar embryos from the nucellus tissue of the ovule ...
.
Uses
Agriculture
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people ...
is almost entirely dependent on angiosperms, which provide virtually all plant-based food, and also provide a significant amount of livestock
Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to ani ...
feed. Of all the families of plants, the Poaceae, or grass family (providing grains), is by far the most important, providing the bulk of all feedstocks (rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
, maize
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of Mexico, indigenous ...
, wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
, barley
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...
, rye, oats, pearl millet, sugar cane, sorghum). The , or legume family, comes in second place. Also of high importance are the Solanaceae, or nightshade family (potato
The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae.
Wild potato species can be found from the southern Uni ...
es, tomato
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word ...
es, and peppers, among others); the Cucurbitaceae, or gourd family (including pumpkins and melon
A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". T ...
s); the Brassicaceae, or mustard plant family (including rapeseed and the innumerable varieties of the cabbage
Cabbage, comprising several cultivars of ''Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.&n ...
species ''Brassica oleracea
''Brassica oleracea'' is a plant species from family Brassicaceae that includes many common cultivars used as vegetables, such as cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, Savoy cabbage, kohlrabi, and gai lan.
It ...
''); and the Apiaceae, or parsley family. Many of our fruits come from the Rutaceae, or rue family (including oranges, lemons, grapefruits, etc.), and the Rosaceae, or rose family (including apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
s, pear
Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the Family (biology), family Rosacea ...
s, cherries, apricots, plums, etc.).
In some parts of the world, certain single species assume paramount importance because of their variety of uses, for example the coconut ('' Cocos nucifera'') on Pacific atoll
An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gro ...
s, and the olive ('' Olea europaea'') in the Mediterranean region.
Flowering plants also provide economic resources in the form of wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin ...
, paper
Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distribu ...
, fiber (cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...
, flax, and hemp, among others), medicines ( digitalis, camphor), decorative and landscaping plants, and many other uses. Coffee
Coffee is a drink prepared from roasted coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content. It is the most popular hot drink in the world.
Seeds of ...
and cocoa
Cocoa may refer to:
Chocolate
* Chocolate
* ''Theobroma cacao'', the cocoa tree
* Cocoa bean, seed of ''Theobroma cacao''
* Chocolate liquor, or cocoa liquor, pure, liquid chocolate extracted from the cocoa bean, including both cocoa butter an ...
are the common beverages obtained from the flowering plants. The main area in which they are surpassed by other plants—namely, coniferous trees ( Pinales), which are non-flowering (gymnosperms)—is timber and paper production.
See also
* List of garden plants
This is a partial list of garden plants, plants that can be cultivated in gardens in North America, listed alphabetically by genus.
A
* ''Abelia''
* '' Abeliophyllum'' ( white forsythia)
* ''Abelmoschus'' (okra)
* ''Abies'' (fir)
* '' Abro ...
* List of plant orders
This article lists the living orders of the Viridiplantae, based primarily on the work of Ruggiero et al. 2015. Living order of Lycophytes and ferns are taken from Christenhusz et al. 2011b and Pteridophyte Phylogeny Group. Living orders of Gymn ...
* List of plants by common name
This is a list of plants organized by their common names. However, the common names of plants often vary from region to region, which is why most plant encyclopedias refer to plants using their scientific names, in other words using binomials or " ...
* List of systems of plant taxonomy
Notes
References
Bibliography
Articles, books and chapters
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1st edition published by Oxford University Press in 1991
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* Cromie, William J. (December 16, 1999)
Harvard University Gazette.
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Websites
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External links
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{{DEFAULTSORT:Flowering Plant
Plant sexuality
Plants
Pollination