Flowering plant

Flowering plant Temporal range: Early Cretaceous (Valanginian)-Recent PreꞒ Ꞓ O S D C P T J K Pg N
oak Forb: orchid Diversity of angiosperms
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Spermatophytes
Clade:	Angiosperms
Groups (APG IV)[1]
Basal angiosperms Amborellales Nymphaeales Austrobaileyales Core angiosperms Clades Magnoliids Monocots Eudicots Orders Chloranthales Ceratophyllales
Synonyms
Anthophyta Cronquist[2] Angiospermae Lindl. Magnoliophyta W.Zimm.[3] Magnolicae Takht.[4]

Flowering plants are

Agriculture is almost entirely dependent on angiosperms, and a small number of flowering plant families supply nearly all plant-based food and livestock feed. Rice, maize, and wheat provide half of the world's calorie intake, and all three plants are cereals from the Poaceae family (colloquially known as grasses). Other families provide materials such as wood, paper and cotton, and supply numerous ingredients for traditional and modern medicines. Flowering plants are also commonly grown for decorative purposes, with certain flowers playing a significant role in many cultures.

Out of the "Big Five"

and is likely to cause many species to become extinct by 2100.

Distinguishing features

Angiosperms are terrestrial vascular plants; like the gymnosperms, they have

seed plants

in several ways.

Feature	Description	Image
Flowers	The seed plants.[9]
Reduced gametophytes, three cells in male, seven cells with eight nuclei in female (except for basal angiosperms)[10]	The gametophytes are smaller than those of gymnosperms. fertilization, which in gymnosperms is up to a year.[12]	Embryo sac is a reduced female gametophyte .
Endosperm	Endosperm forms after fertilization but before the zygote divides. It provides food for the developing embryo, the cotyledons, and sometimes the seedling.[13]
Closed carpel enclosing the ovules .	Once the ovules are fertilised, the carpels, often with surrounding tissues, develop into fruits. Gymnosperms have unenclosed seeds.[14]
Xylem made of vessel elements	Open vessel elements are stacked end to end to form continuous tubes, whereas gymnosperm xylem is made of tapered tracheids connected by small pits.[15]

Diversity

Ecological diversity

• Largest and smallest
• 
  Eucalyptus regnans,
  a tree almost 100 m tall
• 
  Wolffia arrhiza, a rootless floating freshwater plant under 2 mm across

The largest angiosperms are Eucalyptus gum trees of Australia, and Shorea faguetiana, dipterocarp rainforest trees of Southeast Asia, both of which can reach almost 100 metres (330 ft) in height.^[16] The smallest are Wolffia duckweeds which float on freshwater, each plant less than 2 millimetres (0.08 in) across.^[17]

• Photosynthetic and parasitic
• 
  Gunnera captures sunlight for photosynthesis over the large surfaces of its leaves, which are supported by strong veins.
• 
  Orobanche purpurea, a parasitic broomrape with no leaves, obtains all its food from other plants.

Considering their method of obtaining energy, some 99% of flowering plants are

• Hot, cold, wet, dry, fresh, salt
• 
  Carnegiea gigantea, the saguaro cactus, grows in hot dry deserts

  in Mexico and the southern United States.
• 
  Dryas octopetala, the mountain avens, lives in cold arctic and montane habitats in the far north of America and Eurasia.
• 
  Nelumbo nucifera, the sacred lotus, grows in warm freshwater across tropical and subtropical Asia.
• 
  Zostera seagrass grows on the seabed in sheltered coastal waters.

In terms of their environment, flowering plants are cosmopolitan, occupying a wide range of

• Acid, alkaline
• 
  Drosera anglica, a sundew, lives in nutrient-poor acid bogs, deriving nutrients from trapped insects.^[22]
• 
  Gentiana verna, the spring gentian, flourishes in dry limestone habitats.^[23]

Some specialised angiosperms are able to flourish in extremely acid or alkaline habitats. The

• Herbaceous, woody, climbing
• 
  Geranium robertianum, herb-Robert, is an annual or biennial herb of Europe and North America.
• 
  Betula pendula, the silver birch, is a perennial deciduous tree of Eurasia.
• 
  Lianas Austrosteenisia, Parsonsia, and Sarcopetalum climbing trees in Australia

As for their

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,[32] containing over 166,000 species between them in their APG circumscriptions, are:

Evolution

History of classification

The botanical term "angiosperm", from Greek words angeíon (

In 2019, a molecular phylogeny of plants placed the flowering plants in their evolutionary context:^[41]

Internal

The main groups of living angiosperms are:^[42][1]

Angiosperms  Amborellales 1 sp. New Caledonia shrub Nymphaeales c. 80 spp.[43] water lilies & allies Austrobaileyales c. 100 spp.[43] woody plants Magnoliids c. 10,000 spp.[43] 3-part flowers, 1-pore pollen, usu. branch-veined leaves Chloranthales 77 spp.[44] Woody, apetalous Monocots c. 70,000 spp.[45] 3-part flowers, 1 cotyledon , 1-pore pollen, usu. parallel-veined leaves   Ceratophyllales c. 6 spp.[43] aquatic plants Eudicots c. 175,000 spp.[43] 4- or 5-part flowers, 3-pore pollen, usu. branch-veined leaves

Basal angiosperms Core angiosperms

Fossil history

Fossilised

The characteristic feature of angiosperms is the flower. Its function is to ensure

The flower may consist only of these parts, as in wind-pollinated plants like the willow, where each flower comprises only a few stamens or two carpels.^[37] In insect- or bird-pollinated plants, other structures protect the sporophylls and attract pollinators. The individual members of these surrounding structures are known as sepals and petals (or tepals in flowers such as Magnolia 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.^[57][58] The inner series (corolla of petals) is, in general, white or brightly colored, is more delicate in structure, and attracts pollinators by colour, scent, and nectar.^[59][60]

Most flowers are

Double fertilization requires two sperm cells to fertilise cells in the ovule. A pollen grain sticks to the stigma at the top of the pistil, germinates, and grows a long pollen 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.^[66]

Fruit and seed

As the embryo and endosperm develop, the wall of the embryo sac enlarges and combines with the

Other parts of the flower often contribute to forming the fruit. For example, in the apple, the hypanthium forms the edible flesh, surrounding the ovaries which form the tough cases around the seeds.^[68]

Apomixis, setting seed without fertilization, is found naturally in about 2.2% of angiosperm genera.^[69] Some angiosperms, including many citrus varieties, are able to produce fruits through a type of apomixis called nucellar embryony.^[70]

Sexual selection

Adaptive function of flowers

Charles Darwin in his 1878 book The Effects of Cross and Self-Fertilization in the Vegetable Kingdom

Also, Meiosis in flowering plants provides a direct mechanism for repairing DNA through genetic recombination in reproductive tissues.^[74] Sexual reproduction appears to be required for maintaining long-term genomic integrity and only infrequent combinations of extrinsic and intrinsic factors permit shifts to asexuality.^[74] 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.^[73]

Interactions with humans

Practical uses

Agriculture is almost entirely dependent on angiosperms, which provide virtually all plant-based food and livestock feed. Much of this food derives from a small number of flowering plant families.^[75] For instance, half of the world's calorie intake is supplied by just three plants - wheat, rice and maize.^[76]

Flowering plants provide a diverse range of materials in the form of wood, paper, fibers such as cotton, flax, and hemp, medicines such as digoxin and opioids, and decorative and landscaping plants. Coffee and hot chocolate are beverages from flowering plants.^[75]

Cultural uses

Both real and

Relatively few plant diversity assessments currently consider climate change,^[86] yet it is starting to impact plants as 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).^[88] In worst-case scenarios, half of all tree species may be driven extinct by climate change over that timeframe.^[86]

Conservation in this context is the attempt to prevent extinction, whether