Flowering Plants

flowering plants , also known as Angiospermae or Magnoliophyta are the most diverse group of ground plants with 64 orders , 416 families , approximately 13,000 known species and 300,000 known species . [8] Like gymnosperms , angiosperms are seed-producing plants . They differ from gymnosperms incharacteristics including the production of flowers , the endosperm withintheir seeds, and fruits that contain seeds .There are. Etymologically, “angiosperm” literally means a plant that produces seeds within an enclosure; In other words, a fruiting plant. The term comes from the Greek words angeion (‘case’) and sperm (‘seed’).

description

Chamaenerion angustifolium , also known as farweed or rosebay willowherb , is a flowering plant in the willowherb family Onagraceae.

Angiosperm derived features

Angiosperms differ from other seed plants in many ways, which are described in the table below. These distinctive features taken together make angiosperms the most diverse and most commercially important group for many land plants and humans.

Feature	description
flower organ	Flowers, the reproductive organs of flowering plants, are the most notable feature that sets them apart from other seed plants. Flowers provided angiosperms with a means of a more species-specific reproductive system, and therefore a way for different species to evolve more easily without the risk of crossing back with related species. Rapid speciation enabled angiosperms to adapt to a wide range of ecological niches. This has allowed flowering plants to dominate large-scale terrestrial ecosystems. [ citation needed ]
stamens	The stamens are much lighter than the related organs of gymnosperms and have contributed to the diversification of angiosperms through time with special pollination syndromes, such as adaptation to specialized pollinators. The stamens have also been modified over time to prevent self-fertilization, which has allowed further diversification, allowing angiosperms to eventually fill more niches.
Lesser male gametophyte, three cells	Male gametophyte is significantly reduced in size in angiosperms as compared to gymnosperm seed plants. [10] The small size of the pollen shortens the time between pollination – the pollen grain reaches the female plant – and fertilization. In gymnosperms, fertilization can occur up to a year after pollination, while in angiosperms, fertilization begins soon after pollination. [11] The shorter time between pollination and fertilization allows angiosperms to produce seeds earlier after pollination than gymnosperms, giving angiosperms a distinct evolutionary advantage.
spores enclosing closed carpels (can become carpels or carpels and accessory parts of fruit)	The closed carpel of angiosperms also allows adaptation to special pollination syndromes and control. This helps prevent self-fertilization, which leads to increased diversity. Once the ovary is fertilized, the carpel and some of the surrounding tissue develop into a fruit. This fruit often serves as a lure for animals that disperse the seeds. The resulting diffusion presents another advantage for angiosperms in the process of cooperative relationship.
Lesser female gametophyte, seven cells with eight nuclei	The reduced female gametophyte, like the lesser male gametophyte, may have been an adaptation allowing more rapid seed set, which eventually leads to adaptations to such flowering plants as the life-cycle of annual herbicides, Thereby allowing the flowering plants to fill in even more.
endosperm	In general, endosperm formation begins after fertilization and before the first division of the zygote. Endosperm is a highly nutritious tissue that can provide food for the developing embryo, cotyledon, and sometimes the seedling when it first appears.

Vascular anatomy

The stems of angiosperms are composed of seven layers as shown on the right. The amount and complexity of tissue formation in flowering plants is greater than in gymnosperms. The vascular bundles of the stem are arranged such that the annulus form the xylem and phloem.

In dicotyledons, the bundles in the very short stem are arranged in an open ring, separating a central medulla from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active conformational tissue known as the cambium. By the formation of a layer of cambium between the bundles (interfascicular cambium), a complete ring is formed, and regular periodic increase in thickness results in the development of xylem on the inside and phloem on the outside. The soft phloem is crushed, but the hard wood remains and makes up the bulk of the stems and branches of woody perennials. Due to differences in the character of the elements produced at the beginning and end of the season, wood is marked in concentric rings in cross section, one for each season of growth, called annual rings.

Among monocotyledons, bundles are more numerous in young stems and scattered through the ground tissue. They do not have cambium and once formed the stem grows in diameter only in exceptional cases.

Reproductive anatomy

The characteristic feature of angiosperms is flowers. Flowers show remarkable variation in form and detail, and provide the most reliable external features for establishing relationships between angiosperm species. The function of the flower is to ensure the fertilization of the spores and the development of the fruit containing the seeds. ^{[ citation needed ]} The floral apparatus may arise last on a twig or from the axils of the leaf (where the stalk joins the stem). ^{[ citation needed ]} Sometimes, such as in violets, a flower grows singly in a simple leaf-leaf axil. Generally, the flower-bearing part of the plant is separated from the leaf-bearing or vegetative part, and forms a more or less elaborate branching system called the inflorescence.

Two types of germ cells are formed from flowers. Microspores, which will divide to become pollen grains, are “male” cells and are produced in stamens (or microsporophylls). ^{[ citation needed ]} “Female” cells called megaspores, which will divide to become the egg cell (megagametogenesis), are contained in the spore and enclosed in the carcass (or megasporophyll).

The flower may consist of only these parts, as in the willow, where each flower has only a few stamens or two carpels. Normally, other structures are present and serve to protect the sporophyll and to form an attractive envelope for pollinators. 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 bract (the calyx of the mussels) is usually green and leaf-like, and serves to protect the rest of the flower, especially the bud. The inner chain (corolla of the petals) is, in general, white or brightly colored, and more delicate in structure. It serves to attract insect or bird pollinators. Attraction is influenced by colour, smell and nectar, which may be secreted in some part of the flower. The characteristics that attract pollinators are responsible for the popularity of flowers and flowering plants among humans. 

While most flowers are perfect or bisexual (the same flower structure contains both the producing parts of the pollen and the ovule), flowering plants have evolved a number of 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 carapace). Homomorphic flowers may employ a biochemical (physiological) mechanism called self-incompatibility to discriminate between self and non-pollen particles. Alternatively, in dioecious species, the male and female parts are morphologically distinct, developing on separate flowers. ^[12]

Classification

History of classification

The botanical term “angiosperm”, from the Greek words angios ( ἀγγεῖον ‘bottle, vessel’) and sperma ( μα’seed’), was coined as “angiosperm” by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants with seeds enclosed in capsules, distinct from their gymnospermae, or flowering plants with acheneal or schizo-carpic fruits, the whole fruit or each piece of it here considered to be seed and naked. Carl Linnaeus retained both the word and its antonym with the same meaning, but with restricted application, in the name of his class Didynaemia orders. Its use, as with any approach in its modern scope, became possible only after 1827, when Robert Brown established the existence of truly naked ovules in Cycadae and Conifera, ^[13] and applied the name gymnosperms to them. ^{[ citation needed ]}From that time until these gymnosperms were, as always, counted as dicotyledonous plants, the term angiosperms has been used by botanists with varying scope as the group-name of other dicotyledonous plants. Was .

In 1851, Hofmeister discovered changes in the embryo sac of flowering plants, and determined their exact relationship to cryptogamia. This fixed the status of gymnosperms as a separate class from dicotyledon, and the term angiosperm gradually came to be accepted as an appropriate designation for all flowering plants other than gymnosperms, including the classes Dicotyledons and Monocotyledons. . This is the sense in which the word is used today.

In most taxonomies, flowering plants are treated as a coherent group. The most popular descriptive name is angiosperms, with Anthophyta (lit. ‘flower-plant’) second choice (both unranked). The Wettstein system and the Engler system treat them as a subdivision (Angiospermae). suggests the system also treated them as a subdivision (Magnoliophytina), ^[14] but later separated it to Magnoliopsida, Liliopsida, and Rosopsida. The Takhtajan system and the Cronquist system treat them as a division (Magnoliophyta). Dahlgren’s system and Thorne’s system (1992) treat them as a class (Magnoliopsida). The APG system of 1998, and later 2003 ^[15] and 2009 ^[16]The revision treats flowering plants as an unranked clade without a formal Latin name (angiosperms). With the 2009 revision a formal classification was published in which flowering plants rank as a subclass (Magnolidae).

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 now believed to accurately reflect phylogeny. A consensus about how flowering plants should be organized has recently begun to emerge through the work of the Angiosperm Phylogeny Group (APG), which published an influential reclassification of angiosperms in 1998. The update incorporating recent research was published as the APG II System. In 2003, ^[15] the APG III system in 2009, ^[16] [18] and the APG IV system in 2016.

Traditionally, flowering plants are divided into two groups,

• Dicotyledonae or Magnoliopsida
• Monocotyledoneae या Liliopsida

To which the Cronquist system classes Magnoliopsida (“attributed from Magnoliaceae” and Liliopsida (“from Liliaceae”). Other descriptive names permitted by paragraph 16 of the ICBN include Dicotyledones or Dicotyledoneae, and Monocotyledones or Monocotyledoneae, which have a long history of use in plain In English, their members may be called “dicotyledons” (“dicots”) and “monocotyledons” (“monocots”). The Latin behind these names refers to the observation that dicots often have two cotyledons, or embryonic leaves. Each seed. The monocot usually has only one, but the rule is by no means absolute. From a broad clinical point of view, the number of cotyledons is neither particularly easy, nor a reliable character. ^[ citation needed ^]

According to the APG, recent studies suggest that monocots form a monophyletic group (a clade), but that dicots are paraphyletic. Nevertheless, the majority of dicot species fall into one clade, the eudicots or tricolpates in another major clade, and most of the remainder fall into the magnoliids, there are about 9,000 species. The rest comprise a paraphyletic group of early branching taxa known collectively as basal angiosperms, as well as the families Ceratophyllaceae and Chloranthaceae. ^{[ citation needed ]}

Modern classification

There are eight groups of living angiosperms:

• Basal angiosperms (ANA: Amborella , Nymphales, Austrobeliales)
  • amborella , the same species of shrub from New Caledonia;
  • Nymphaeales, about 80 species, ^[19] water lilies and Hydatellaceae;
  • Austrobeliales, about 100 species of woody plants from different parts of the world ^[19]
• Core angiosperms (mesangiosperms) ^[17]
  • Chloranthales, 77 known species of aromatic plants with toothed leaves ^[20] ;
  • Magnoliids, about 9,000 species, ^[19] which have quarterly flowers, pollen with a perforation, and usually branching leaves—eg magnolias, bay laurel, and pepper;
  • monocots, about 70,000 species, ^[19] consisting of trifoliate flowers, a single cotyledon, pollen with a single pore, and usually parallel-veined leaves—for example grasses, orchids, and palms;
  • Ceratophyllum , about 6 species of aquatic plants ^[19] , is perhaps most familiar as aquarium plants;
  • Eudicots, about 175,000 species, ^[19] containing 4- or 5-merus flowers, pollen with three sessile, and usually branching-veined leaves—for example sunflower, petunia, buttercup, apple and oak .

The exact relationship between these eight groups is not yet clear, although it is agreed that the first three groups to separate from the ancestral angiosperms are Amborelles, Nymphaeales and Austrobales (basal angiosperms) ^[21] of the remaining five groups (core angiosperms). were. , relationships between the three most widespread groups remain unclear (magnoliids, monocots and eudicots). Zeng and colleagues (Figure 1) describe four competing schemes. ^[22] Eudicots and monocots are the largest and most diverse, accounting for ~75% and 20% of angiosperm species, respectively. Some analyzes separate magnoliids first, others monocots. ^[23] Ceratophyllum appears to be grouped with eudicots rather than monocots. APG IV retains the overall higher order relationship described in APG III.

Evolutionary history

Paleozoic

Fossil spores suggest that land plants (embryophytes) have existed for at least 475 million years. ^[24] Early land plants reproduced sexually with the flagellated, floating spermatozoa from which they evolved, like the green algae. ^{[ citation needed ]} An adaptation to terrestrialization was the development of meiosporangia directly for dispersal by spores into new habitats. ^{[ citation needed ]} This characteristic is lacking in the descendants of their closest algal relatives, the Charophysian green algae. Subsequent terrestrial adaptation occurred with retention of the gametophyte, the delicate, avascular sexual stage, within the tissues of the vascular sporophyte. ^{[ citation needed ]}This resulted from the germination of the spore within the spore rather than releasing the spore, as is the case in non-seed plants. A current example of how this can happen can be seen in precocious spore germination in Selaginella , spike-moss. The consequence for the ancestors of angiosperms was enclosing them in a case, the seed.

The apparently sudden appearance in the fossil record of almost modern flowers and in great diversity initially posed such a problem to the theory of evolution that Charles Darwin called it an “abominable mystery”. ^[25] However, the fossil record has increased significantly since Darwin’s time, and more recently discovered angiosperm fossils such as Archifractus , along with further discoveries of fossil gymnosperms, suggest how angiosperm characteristics are arranged in a series of stages. can be obtained. ^{[ citation needed ]}Several groups of extinct gymnosperms, especially seed ferns, have been proposed as ancestors of flowering plants, but there is no consistent fossil evidence showing how flowers evolved, and botanists still consider it a mystery. considered as. ^[26] Some older fossils, such as the Upper Triassic Sanmiguelia lewisi , have been suggested.

Earlier seed plants, such as ginkgo, and conifers (such as pines and firs), did not produce flowers. The pollen grains (male gametophytes) of ginkgoes and cycads produce a pair of flagellated, mobile sperm cells that “swim” the female and her eggs down the developing pollen tube.

Oleianone, a secondary metabolite produced by many flowering plants, has been found in Permian deposits of that era with fossils of gigantopterids. ^[27] [28] Gigantopterids are a genus of extinct seed plants that share many morphological traits with flowering plants, although it is not known whether they are flowering plants themselves. ^{[ citation needed ]}

Triassic and Jurassic

Based on current evidence, some propose that the ancestors of 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 earlier date for their origin. ^[29] The close relationship between angiosperms and gnophytes, proposed on the basis of morphological evidence, has recently been disputed on the basis of molecular evidence suggesting that gnophytes are instead more closely related to other gymnosperms. ^[30] [31]

The fossil plant species Nanjingthus dendrostyla from Early Jurassic China shares many characteristically angiosperm features, such as a concentric vessel with an ovule, and thus may represent a crown-group or a stem-group angiosperm. ^[32] However, these have been disputed by other researchers, who argue that the structures are incorrectly dissected conical cones.

The evolution of seed plants and later angiosperms appears to be the result of two distinct rounds of whole-genome duplication events. ^[35] These occurred between 319 million years ago and 192 million years ago . Another possible whole-genome duplication event 160 million years ago probably formed the ancestral line that gave rise to all modern flowering plants. ^[36] That phenomenon was studied by sequencing the genome of an ancient flowering plant, Amborella trichopoda , ^[37] and directly addresses Darwin’s “disgusting mystery”.

One study has suggested that the early-Middle Jurassic plant Schamisneria , traditionally considered a type of ginkgo, may be the earliest known angiosperm, or at least a close relative. ^[38]

Cretaceous

While Earth was previously dominated by ferns and conifers, angiosperms appeared and spread rapidly during the Cretaceous. They now comprise about 90% of all plant species, including most food crops. ^[39] It has been proposed that the rapid increase in dominance of angiosperms was due to a reduction in the size of their genomes. During the early Cretaceous period, only angiosperms underwent rapid genome downsizing, whereas the genome sizes of ferns and gymnosperms remained unchanged. Smaller genomes—and smaller nuclei—allow faster rates of cell division and smaller cells. Thus, species with smaller genomes can pack more, smaller cells—especially in veins and stomata ^{[ citation needed ]—}in the quantity of the given leaf. Genome downsizing therefore facilitated a higher rate of leaf gas exchange (transpiration and photosynthesis) and a faster rate of evolution. This would have countered some of the negative physiological effects of genome duplication, helped carbon dioxide uptake despite the concurrent decline in atmospheric CO _{concentrations} , and allowed flowering plants to outcompete other land plants. ^[40]

The oldest known fossils definitively attributed to angiosperms are reticulated monosulcate pollen from the Late Velanginian (Early or Lower Cretaceous – 140 to 133 million years ago) of Italy and Israel, likely representatives of basal angiosperm grades. ^[33]

The earliest known macrofossil identified as an angiosperm, Archaefructus lioningensis , is dated to about 125 million years BP (Cretaceous period), ^[41] while the pollen is believed to be of angiosperm origin, with the fossil record dated to about 130 million years BP. leads to. ^[42] with Montsechia representing the earliest flower at that time. ^[43]

Flowers encased in amber were found in 2013 and dated to 100 million years earlier than present. Amber had stopped the act of sexual reproduction in the process of being. Microscopic images showing the tubes coming out of the pollen and penetrating the stigma of the flower. The pollen was sticky, suggesting that it was carried by insects. ^[44] In August 2017, scientists presented a detailed description and 3D model image of what the first flower looked like, and hypothesized that it may have been around 140 million years ago. ^[45] [46] A Bayesian analysis of 52 angiosperm taxa suggested that the angiosperm crown group evolved between 178 million years ago and 198 million years ago . ^[47]

Recent DNA analysis based on molecular systems ^[48] [ 49] has shown that Amborella trichopoda, found on the Pacific island of New Caledonia, is related to a sister group to other flowering plants, and from morphological studies ^[50] Turns out it has characteristics that may have been characteristic of early flowering plants. The orders Amborellales, Nymphaeales, and Austrobaileyales separated as distinct species from the remaining angiosperm clade at a very early stage in flowering plant development. ^[51]

The great angiosperm radiation, when a great diversity of angiosperms appears in the fossil record, occurred in the mid-Cretaceous (about 100 million years ago). However, a 2007 study ^[52] estimated that the five most recent groups split into eight main groups about 140 million years ago. (genus Ceratophyllum , family Chloranthaceae, eudicots, magnoliids, and monocots).

It is generally believed that the function of flowers, from the very beginning, was to involve mobile animals in their reproductive processes. that is, pollen can be dispersed even if the flower is not brightly colored or oddly shaped to attract animals; However, by expending the energy required to create such traits, angiosperms can obtain the help of animals and, thus, reproduce more efficiently.

Island genetics provides a 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 require lower transitional forms. Flowering plants may have developed in an isolated setting, like an island or island chain, where the plants bearing them were able to develop a highly specialized relationship with certain animals (for example, a wasp). Such a relationship, with a hypothetical wasp carrying pollen from plant to plant in the way fig wasps do today, may have resulted in the evolution of a high degree of specialization in both the plant and their partners. Note that the wasp example is not accidental; bees, which, it is believed,^[53]

Animals are also involved in the distribution of seeds. The fruit, which is formed from growing parts of the flower, is often a seed-dispersing device that attracts or otherwise disturbs animals to eat it, by chance scattering the seeds it contains (see frugivory). . Although many such mutualistic relationships remain too fragile to survive competition and spread widely, the flower proved to be an unusually effective means of reproduction, becoming the dominant form of land plant life ( whatever its origin). ^{[ citation needed ]}

Flower ontogeny uses a combination of genes normally responsible for creating new shoots. ^[54]The most primitive flowers probably have a variable number of flower parts, often separate from (but in contact with) each other. The flowers grow in a spiral pattern, to be bisexual (in plants, this means that there are both male and female parts on the same flower), and dominated by the ovary (female part). As flowers evolved, some variations fused the developed parts together, with a much more distinct number and design, and specific sexes per flower or plant, or at least “ovary-inferior”. Flowers continue to grow today; Modern flowers have been so deeply influenced by humans that some of them cannot be pollinated in nature. Many modern domesticated flower species were formerly simple weeds, which only cropped up when the ground was eroded. Some of them tended to grow with human crops, perhaps already having symbiotic companion plant relationships with them,^[55]

Some paleontologists have even proposed that flowering plants, or angiosperms, may have evolved because of interactions with dinosaurs. One of the strong proponents of this idea is Robert T. Baker. He proposes that herbivorous dinosaurs, along with their eating habits, provided a selective pressure on plants, to which adaptations were successful in either preventing or countering hunting by herbivores. ^[56]

By the late Cretaceous, angiosperms first appear in environments occupied by ferns and cycadophytes, but large canopy-forming trees replaced conifers as the dominant trees, only 66 million years ago or later, during the early Cretaceous. were near the end. Paleogene. ^[57] The radiation of herbivorous angiosperms occurred much later. ^[58] Nevertheless, many fossil plants identified as modern families (including beech, oak, maple, and magnolia) had already appeared by the Late Cretaceous. Flowering plants appeared in Australia about 126 million years ago. It also pushed the age of ancient Australian vertebrates, then a south polar continent, to 126–110 million years old. ^[43]

Gallery of photos

• Poster of twelve different species of flowers of the Asteraceae family
• lupinus pilosus
• pink rose bud

Variety

The number of flowering plant species is estimated to be between 250,000 and 400,000. ^{[59] [60] [61]} This compares to about 12,000 species of mosses ^[62] or 11,000 species of pteridophytes, ^[63] indicating that flowering plants are much more diverse. The number of families in APG (1998) was 462. This is not fixed in APG II ^{[15] (2003);} The maximum is 457, but within this number there are 55 alternative segregations, so that the minimum number of families in this system is 402. There are 415 families in APG III (2009). ^[16] [64]Compared to the APG III system, the APG IV system recognizes five new orders (Boraginales, Deleniales, Icanales, Meteniusales and Wahliales) along with a few families, making a total of 64 angiosperm orders and 416 families. ^[65] The diversity of flowering plants is not evenly distributed. Almost all species belong to the eudicot (75%), monocot (23%), and magnolid (2%) clades. The remaining 5 groups have a total of over 250 species; That is, less than 0.1% of the diversity of flowering plants, divided into 9 families. Of the 443 families of flowering plants by species, 43 are the most diverse, ^[66] in their apogee range,

1. Asteraceae or Compositae (daisy family): 22,750 species;
2. Orchidaceae (orchid family): 21,950;
3. Fabaceae or Leguminosae (bean family): 19,400;
4. Rubiaceae (crazy family): 13,150; ^[67]
5. Poaceae or Gramini (grass family): 10,035;
6. Lamiaceae or Labiatae (mint family): 7,175;
7. Euphorbiaceae (succulent plant family): 5735;
8. Melastomataceae या Melastomaceae ( melastome परिवार): 5005;
9. Myrtaceae (Henna family): 4,625;
10. Apocynaceae (dogbane family): 4555;
11. Cyperaceae (sedge family): 4,350;
12. Malvesi (Malo family): 4,225;
13. long (Arum family): 4,025;
14. Ericaceae (heath family): 3,995;
15. Gesneriaceae ( Gesneriad family): 3,870;
16. Apiaceae or Umbelliferae (Parsley family): 3,780;
17. Brassicaceae or Cruciferae (cabbage family): 3,710:
18. Piperaceae (pepper family): 3,600;
19. Bromeliaceae (bromeliad family): 3,540;
20. Acanthaceae (acanthus family): 3,500;
21. Rosaceae ( rose family): 2,830;
22. Boraginaceae (borage family): 2,740;
23. Urticaceae (nettle family): 2,625;
24. Ranunculaceae (buttercup family): 2,525;
25. Lauraceae (laurel family): 2,500;
26. Solanaceae (nightshade family): 2,460;
27. Campanulaceae (bellflower family): 2,380;
28. Arecaceae (palm family): 2,361;
29. Annonaceae (custard apple family): 2,220;
30. Caryophyllaceae (pink family): 2,200;
31. Orobanchaceae (Broomrape family): 2,060;
32. Amaranthaceae ( Amaranth family): 2,050;
33. Iridaceae ( Iris family): 2,025;
34. Aizoaceae or Ficoidaceae (snow plant family): 2,020;
35. Rutsei (Rue family): 1,815;
36. Phyllanthaceae ( phyllanthus परिवार): 1,745;
37. Scrophulariaceae (fig family): 1,700;
38. Gentianaceae (Gentian family): 1,650;
39. Convolvulaceae (bindweed family): 1,600;
40. Proteaceae ( Protea family): 1,600;
41. Sapindaceae (soapberry family): 1,580;
42. Cactaceae (Cactus family): 1500;
43. Araliaceae ( Aralia or ivy family): 1,450.

Of these, the Orchidaceae, Poaceae, Cyperaceae, Araceae, Bromeliaceae, Arecaceae, and Iridaceae are the monocotyledon families; Piperaceae, Lauraceae, and Annonaceae are magnolid dicots; The rest of the family are eudicots.

Reproduction

Fertilization and embryogenesis

Fruits and seeds

As the embryo and endosperm develop within the embryo sac, the sac wall enlarges and forms the seed coat together with the nucellus (which is similarly growing) and the integument . The wall of the ovary develops to form the fruit or pericarp, the form of which is closely related to the type of seed dispersal system. ^[68]

Often, the effects of fertilization are felt beyond the ovary, and other parts of the flower participate in fruit formation, for example, the floral receptacle in apples, strawberries, and others. ^{[ citation needed ]}

The character of the seed coat bears a definite relation to the fruit. They protect the embryo and aid in proliferation; They can also directly promote germination. In plants with insoluble fruits, in general, the fruit protects the embryo and secures propagation. In this case, the seed coat is only slightly developed. If the fruit is wilted and the seed is open, then in general, the seed-coat is well developed, and should discharge the functions otherwise performed by the fruit. ^{[ citation needed ]}

In some cases, such as in the Asteraceae family, species have evolved to exhibit heterocarpy, or the production of different fruit forms. ^[69] These fruit forms produced from a single plant vary in size and shape, affecting dispersal extent and germination rate. ^[69] These fruit forms are adapted to different environments, increasing their chances of survival. ^[69]

Meiosis

Flowering plants produce gametes using a special cell division called meiosis. Meiosis occurs in the ovule (a structure within the ovary that is located within the pistil in the center of the flower) (see figure labeled “Angiosperm Lifecycle”). A diploid cell (megaspore mother cell) in the ovule undergoes meiosis (involving two successive cell divisions) and produces four cells (megaspore) with a haploid nucleus. ^[70] It is believed that the basal chromosome number in angiosperms is n = 7. ^[71]One of these four cells (megaspore) then undergoes three successive mitosis to produce an immature embryo sac (megagametophyte) with eight haploid nuclei. Subsequently, these nuclei are separated by cytokinesis into individual cells to produce 3 antipodal cells, 2 synergid cells, and an egg cell. Two polar nuclei remain in the central cell of the embryo sac. ^{[ citation needed ]}

Pollen is also produced by meiosis in the male anther (Microsporangium). During meiosis, a diploid microspore mother cell undergoes two successive meiosis to produce 4 haploid cells (microspores or male gametes). Each of these microspores, after further mitoses, becomes a pollen grain (microgametophyte) consisting of two haploid germ (sperm) cells and a tube nucleus. When a pollen grain comes in contact with the female stigma, the pollen grain forms a pollen tube that develops downward into the ovary. In the act of fertilization, a male sperm nucleus fuses with the nucleus of a female egg to form a diploid zygote which can then develop into an embryo within the newly formed seed. Upon germination of the seed, a new plant can grow and mature. ^{[ citation needed ]}

The adaptive function of meiosis is currently a matter of debate. An important event during meiosis in a diploid cell is the pairing of homologous chromosomes and homologous recombination (exchange of genetic information) between homologous chromosomes. This process promotes the production of increased genetic diversity among progeny and encourages the transfer of recombinant repair of DNA damage to the offspring. To explain the adaptive function of meiosis in flowering plants, some authors emphasize diversity ^[72] and others emphasize DNA repair. ^[73]

Apomixis

Apomixis (reproduction through asexually produced seeds) occurs naturally in about 2.2% of angiosperm genera. ^[74] A variant of apomixis, gametophytic apomixis found in a dandelion species ^[75] , involves the formation of an unreduced embryo sac without fertilization due to incomplete meiosis (apomeiosis) and the development of an embryo from the unreduced egg inside the embryo sac. ( parthenogenesis ) ^{[ citation needed ]}

Some angiosperms, including many citrus cultivars, are capable of producing fruit through a type of apomixis known as the nucellar embryo. ^[76]

Use

Agriculture is almost entirely dependent on angiosperms, which provide almost all plant-based food, as well as a significant amount of livestock feed. Of all the plant families, the Poaceae, or grass family (providing cereals), is by far the most important, providing the bulk of all feedstocks (rice, maize, wheat, barley, rye, oats, pearl millet, sugarcane). . Fever ). The Fabaceae, or legume family, comes in second. The Solanaceae, or nightshade family (potatoes, tomatoes, and peppers, among others) are also of high importance; Cucurbitaceae, or the gourd family (including pumpkins and melons); Brassicaceae, or mustard plant family (including rapeseed and myriad varieties of cabbage species Brassica cabbage, and Apiaceae, or the 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 apples, pears, cherries, apricots, plums, etc.). ^{[ citation needed ]}

In some parts of the world, a few single species are of paramount importance due to their wide variety of uses, for example the coconut ( Cocos nucifera ) on the Pacific atoll and the olive ( Olea europaea ) in the Mediterranean region . ^[77]

Flowering plants also provide economic resources in the form of wood, paper, fibers (cotton, flax, and hemp, among others), medicines (digitalis, camphor), ornamental and landscaping plants, and many other uses. Coffee and cocoa are common beverages derived from flowering plants. The main areas in which they overtake other plants—namely, coniferous trees (Pineales), which are non-flowering (gymnosperms)—produce wood and paper.