Flowering plant

Flowering plantsareplantsthat bearflowersandfruits, and form thecladeAngiospermae(/ˌændʒiəˈspərmiː/).The term 'angiosperm' is derived from theGreekwords ἀγγεῖον /angeion('container, vessel') and σπέρμα /sperma('seed'), meaning that theseedsare enclosed within a fruit. The group was formerly calledMagnoliophyta.
Angiosperms are by far the most diverse group ofland plantswith 64orders, 416families, approximately 13,000 knowngeneraand 300,000 knownspecies.They include allforbs(flowering plants without awoodystem),grassesand grass-like plants, a vast majority ofbroad-leaved trees,shrubsandvines, and mostaquatic plants. Angiosperms are distinguished from the other majorseed plantclade, thegymnosperms, by havingflowers,xylemconsisting ofvessel elementsinstead oftracheids,endospermwithin their seeds, and fruits that completely envelop the seeds. The ancestors of flowering plants diverged from the common ancestor of all living gymnosperms before the end of theCarboniferous, over 300 million years ago. In theCretaceous, angiospermsdiversified explosively, becoming the dominant group of plants across the planet.
Agricultureis almost entirely dependent on angiosperms, and a small number of flowering plant families supply nearly all plant-basedfoodandlivestockfeed.Rice,maizeandwheatprovide half of the world'sstaplecalorieintake, and all three plants arecerealsfrom thePoaceaefamily (colloquially known as grasses). Other families provide important industrialplant productssuch aswood,paperandcotton, and supply numerous ingredients forbeverages,sugar production,traditional medicineand modernpharmaceuticals. Flowering plants are also commonly grown fordecorative purposes, with certain flowers playing significant cultural roles in many societies.
Out of the "Big Five"extinction eventsin Earth's history, only theCretaceous–Paleogene extinction eventhad occurred while angiosperms dominated plant life on the planet. Today, theHolocene extinctionaffects allkingdomsofcomplex lifeon Earth, and conservation measures are necessary to protect plants in their habitats in the wild (in situ), or failing that,ex situinseed banksor artificial habitats likebotanic gardens. Otherwise, around 40% of plant species may becomeextinctdue to human actions such ashabitat destruction, introduction ofinvasive species, unsustainablelogging,land clearingandoverharvestingofmedicinalorornamental plants. Further,climate changeisstarting to impact plantsand is likely to cause many species to become extinct by 2100.
Angiosperms are terrestrial vascular plants; like the gymnosperms, they haveroots,stems,leaves, andseeds. They differ from otherseed plantsin several ways.
The largest angiosperms areEucalyptusgum trees of Australia, andShorea faguetiana, dipterocarp rainforest trees of Southeast Asia, both of which can reach almost 100 metres (330 ft) in height.The smallest areWolffiaduckweeds which float on freshwater, each plant less than 2 millimetres (0.08 in) across.
Considering their method of obtaining energy, some 99% of flowering plants arephotosyntheticautotrophs, deriving their energy from sunlight and using it to create molecules such assugars. The remainder areparasitic, whetheron fungilike theorchidsfor part or all of their life-cycle,oron other plants, either wholly like the broomrapes,Orobanche, or partially like the witchweeds,Striga.
In terms of their environment, flowering plants are cosmopolitan, occupying a wide range ofhabitatson land, in fresh water and in the sea. On land, they are the dominant plant group in every habitat except for frigid moss-lichentundraandconiferous forest.Theseagrassesin theAlismatalesgrow in marine environments, spreading withrhizomesthat grow through the mud in sheltered coastal waters.
Some specialised angiosperms are able to flourish in extremely acid or alkaline habitats. Thesundews, many of which live in nutrient-poor acidbogs, arecarnivorous plants, able to derive nutrients such asnitratefrom the bodies of trapped insects.Other flowers such asGentiana verna, the spring gentian, are adapted to the alkaline conditions found oncalcium-richchalkandlimestone, which give rise to often drytopographiessuch aslimestone pavement.
As for theirgrowth habit, the flowering plants range from small, softherbaceous plants, often living asannualsorbiennialsthat set seed and die after one growing season,to largeperennialwoodytreesthat may live for many centuries and grow to many metres in height. Some species grow tall without being self-supporting like trees byclimbingon other plants in the manner ofvinesorlianas.
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 ofmossand 11,000 species ofpteridophytes.TheAPG systemseeks to determine the number offamilies, mostly bymolecular phylogenetics. In the 2009APG IIIthere were 415 families.The 2016APG IVadded five new orders (Boraginales, Dilleniales, Icacinales, Metteniusales and Vahliales), along with some new families, for 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 25 most species-rich of 443 families,containing over 166,000 species between them in their APG circumscriptions, are:
The botanical term "angiosperm", from Greek wordsangeíon(ἀγγεῖον'bottle, vessel') andspérma(σπέρμα'seed'), was coined in the form "Angiospermae" byPaul Hermannin 1690, including only flowering plants whose seeds were enclosed in capsules.The term angiosperm fundamentally changed in meaning in 1827 withRobert Brown, when angiosperm came to mean a seed plant with enclosed ovules.In 1851, withWilhelm Hofmeister's work on embryo-sacs, Angiosperm came to have its modern meaning of all the flowering plants including Dicotyledons and Monocotyledons.TheAPG systemtreats 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 the subclass Magnoliidae.From 1998, theAngiosperm Phylogeny Group(APG) has reclassified the angiosperms, with updates in theAPG II systemin 2003,theAPG III systemin 2009,and theAPG IV systemin 2016.
In 2019, amolecular phylogenyofplantsplaced the flowering plants in their evolutionary context:
The main groups of living angiosperms are:
In 2024, Alexandre R. Zuntini and colleagues constructed a tree of some 6,000 flowering plant genera, representing some 60% of the existing genera, on the basis of analysis of 353 nuclear genes in each specimen. Much of the existing phylogeny is confirmed; therosidphylogeny is revised.
Fossilisedsporessuggest that land plants (embryophytes) have existed for at least 475 million years.However, angiospermsappear suddenlyand in great diversity in the fossil record in theEarly Cretaceous(~130 mya).Claimed records of flowering plants prior to this are not widely accepted.Molecular evidence suggests that the ancestors of angiosperms diverged from thegymnospermsduring the lateDevonian, about 365 million years ago.The origin time of thecrown groupof flowering plants remains contentious.By the Late Cretaceous, angiosperms appear to have dominated environments formerly occupied byfernsand gymnosperms. Largecanopy-forming trees replacedconifersas the dominant trees close to the end of the Cretaceous, 66 million years ago.The radiation of herbaceous angiosperms occurred much later.
The characteristic feature of angiosperms is the flower. Its function is to ensurefertilizationof theovuleand development offruitcontainingseeds.It may arise terminally on a shoot or from theaxilof a leaf.The flower-bearing part of the plant is usually sharply distinguished from the leaf-bearing part, and forms a branch-system called aninflorescence.
Flowers produce two kinds of reproductive cells.Microspores, which divide to becomepollen grains, are the male cells; they are borne in thestamens.The female cells,megaspores,divide to become the egg cell. They are contained in theovuleand enclosed in thecarpel; one or more carpels form thepistil.
The flower may consist only of these parts, as inwind-pollinatedplants like thewillow, where each flower comprises only a fewstamensor two carpels.Ininsect-orbird-pollinatedplants, other structures protect thesporophyllsand attract pollinators. The individual members of these surrounding structures are known assepalsandpetals(ortepalsin flowers such asMagnoliawhere 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, is more delicate in structure, and attracts pollinators by colour,scent, andnectar.
Most flowers arehermaphroditic, producing both pollen and ovules in the same flower, but some use other devices to reduce self-fertilization. Heteromorphic flowers have carpels and stamens of differing lengths, so animalpollinatorscannot easily transfer pollen between them. Homomorphic flowers may use a biochemicalself-incompatibilityto discriminate between self and non-self pollen grains.Dioeciousplants such ashollyhave male and female flowers on separate plants.Monoeciousplants have separate male and female flowers on the same plant; these are often wind-pollinated,as inmaize,but include some insect-pollinated plants such asCucurbitasquashes.
Double fertilizationrequires two sperm cells to fertilise cells in the ovule. Apollengrain sticks to the stigma at the top of the pistil, germinates, and grows a longpollen tube. 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. The pollen tube grows from the stigma, down the style and into the ovary. When it reaches the micropyle of the ovule, it digests its way into one of the synergids, releasing its contents including the sperm cells. The synergid that the cells were released into degenerates; one sperm makes its way to fertilise the egg cell, producing a diploid (2n) zygote. The second sperm cell fuses with both central cell nuclei, producing a triploid (3n) cell. The zygote develops into an embryo; the triploid cell develops into the endosperm, the embryo's food supply. The ovary develops into a fruit and each ovule into a seed.
As the embryo and endosperm develop, the wall of the embryo sac enlarges and combines with thenucellusandintegumentto form theseed coat. The ovary wall develops to form the fruit orpericarp, whose form is closely associated with type of seed dispersal system.
Other parts of the flower often contribute to forming the fruit. For example, in theapple, thehypanthiumforms the edible flesh, surrounding the ovaries which form the tough cases around the seeds.
Apomixis, setting seed without fertilization, is found naturally in about 2.2% of angiosperm genera.Some angiosperms, including manycitrusvarieties, are able to produce fruits through a type of apomixis callednucellar embryony.
Charles Darwin in his 1878 book The Effects of Cross and Self-Fertilization in the Vegetable Kingdomin the initial paragraph of chapter XII noted "The first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross-fertilisation is beneficial and self-fertilisation often injurious, at least with the plants on which I experimented."Flowersemerged in plant evolution as an adaptation for the promotion of cross-fertilisation(outcrossing), a process that allows the masking of deleteriousmutationsin thegenomeof progeny.  The masking effect is known asgenetic complementation.Meiosisin flowering plants provides a direct mechanism forrepairing DNAthrough genetic recombination in reproductive tissues.Sexual reproductionappears to be required for maintaining long-termgenomicintegrity and only infrequent combinations of extrinsic and intrinsic factors permit shifts to asexuality.Thus the two fundamental aspects of sexual reproduction in flowering plants, cross-fertilization (outcrossing) and meiosis  appear to be maintained respectively by the advantages of genetic complementation and recombinational repair.
Agricultureis almost entirely dependent on angiosperms, which provide virtually all plant-based food andlivestockfeed. Much of this food derives from a small number of flowering plant families.For instance, half of the world'scalorieintake is supplied by just three plants –wheat,riceandmaize.
Flowering plants provide a diverse range of materials in the form ofwood,paper, fibers such ascotton,flax, andhemp,medicinessuch asdigoxinandopioids, and decorative and landscaping plants.Coffeeandhot chocolateare beverages from flowering plants (in theRubiaceaeandMalvaceaerespectively).
Both real andfictitious plantsplay a wide variety ofroles in literature and film.Flowers are the subjects of many poems by poets such asWilliam Blake,Robert Frost, andRabindranath Tagore.Bird-and-flower painting(Huaniaohua) is a kind ofChinese paintingthat celebrates the beauty of flowering plants.Flowers have beenused in literature to convey meaningby authors includingWilliam Shakespeare.Flowers are used in a variety of art forms which arrange cut or living plants, such asbonsai,ikebana, and flower arranging.Ornamental plantshave sometimes changed the course of history, as intulipomania.Many countries and regions havefloral emblems; a survey of 70 of these found that the most popular flowering plant family for such emblems is Orchidaceae at 15.7% (11 emblems), followed by Fabaceae at 10% (7 emblems), and Asparagaceae, Asteraceae, and Rosaceae all at 5.7% (4 emblems each).
Human impact on the environmenthas driven a range of species extinct andis threatening even more today. Multiple organizations such asIUCNandRoyal Botanic Gardens, Kewsuggest that around 40% of plant species are threatened with extinction.The majority are threatened byhabitat loss, but activities such as logging of wild timber trees and collection of medicinal plants, or the introduction of non-nativeinvasive species, also play a role.
Relatively few plant diversity assessments currently considerclimate change,yet it isstarting to impact plantsas well. About 3% of flowering plants are very likely to be driven extinct within a century at 2 °C (3.6 °F) of global warming, and 10% at 3.2 °C (5.8 °F).In worst-case scenarios, half of all tree species may be driven extinct by climate change over that timeframe.
Conservation in this context is the attempt to prevent extinction, whetherin situby protecting plants and their habitats in the wild, orex situinseed banksor as living plants.Some 3000botanic gardensaround the world maintain living plants, including over 40% of the species known to be threatened, as an "insurance policy against extinction in the wild."TheUnited Nations'Global Strategy for Plant Conservationasserts that "without plants, there is no life".It aims to "halt the continuing loss of plant diversity" throughout the world.