Microspore
Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote. Megaspores are structures that are part of the alternation of generations in many seedless vascular cryptogams, all gymnosperms and all angiosperms. Plants with heterosporous life cycles using microspores and megaspores arose independently in several plant groups during the Devonian period. Microspores are haploid, are produced from diploid microsporocytes by meiosis; the microspore has three different wall layers. The outer layer is called the perispore, the next is the exospore, the inner layer is the endospore; the perispore is the thickest of the three layers while the exospore and endospore are equal in width. In heterosporous seedless vascular plants, modified leaves called microsporophylls bear microsporangia containing many microsporocytes that undergo meiosis, each producing four microspores.
Each microspore may develop into a male gametophyte consisting of a somewhat spherical antheridium within the microspore wall. Either 128 or 256 sperm cells with flagella are produced in each antheridium; the only heterosporous ferns are aquatic or semi-aquatic, including the genera Marsilea, Pilularia and Azolla. Heterospory is known in the lycopod genus Selaginella and in the quillwort genus Isoëtes. Types of seedless vascular plants: Ferns Spikemosses Quillworts In seed plants the microspores develop into pollen grains each containing a reduced, multicellular male gametophyte; the megaspores, in turn, develop into reduced female gametophytes that produce egg cells that, once fertilized, develop into seeds. Pollen cones or microstrobili develop toward the tips of the lower branches in clusters up to 50 or more; the microsporangia of gymnosperms develop in pairs toward the bases of the scales, which are therefore called microsporophylls. Each of the microsporocytes in the microsporangia undergoes meiosis, producing four haploid microspores.
These develop into each consisting of four cells and a pair of external air sacs. The air sacs give the pollen grains added buoyancy. Types of Gymnosperms: Conifers Pines Ginkgos Cycads Gnetophytes As the anther of a flowering plant develops, four patches of tissue differentiate from the main mass of cells; these patches of tissue contain many diploid microsporocyte cells, each of which undergoes meiosis producing a quartet of microspores. Four chambers lined with nutritive tapetal cells are visible by the time the microspores are produced. After meiosis, the haploid microspores undergo several changes: The microspore divides by mitosis producing two cells; the first of the cells is formed inside the second larger cell. The members of each part of the microspores separate from each other. A double-layered wall develops around each microspore; these steps occur in sequence and when complete, the microspores have become pollen grains. Although it is not the usual route of a microspore, this process is the most effective way of yielding haploid and double haploid plants through the use of male sex hormones.
Under certain stressors such as heat or starvation, plants select for microspore embryogenesis. It was found. In the anther, after a microspore undergoes microsporogenesis, it can deviate towards embryogenesis and become star-like microspores; the microspore can go one of four ways: Become an embryogenic microspore, undergo callogenesis to organogenesis, become a pollen-like structure or die. Microsporangium Spore Megaspore
Canna (plant)
Canna is a genus of 10 species of flowering plants. The closest living relations to cannas are the other plant families of the order Zingiberales, the Zingiberaceae, Marantaceae, Strelitziaceae, etc. Canna is the only genus in the family Cannaceae; the APG II system of 2003 assigns it in the monocots. Plants have large foliage and horticulturists have turned it into a large-flowered garden plant, it is used in agriculture as a rich source of starch for human and animal consumption. Although a plant of the tropics, most cultivars have been developed in temperate climates and are easy to grow in most countries of the world as long as they receive at least 6–8 hours average sunlight during the summer, are moved to a warm location for the winter. See the Canna cultivar gallery for photographs of Canna cultivars; the name Canna reed. The plants are large subtropical perennial herbs with a rhizomatous rootstock; the broad, alternate leaves that are such a feature of this plant, grow out of a stem in a long, narrow roll and unfurl.
The leaves are solid green, but some cultivars have glaucose, maroon, or variegated leaves. The flowers are composed of three sepals and three petals that are noticed by people, they are small and hidden under extravagant stamens. What appear to be petals are the modified stamens or staminodes; the staminodes number 3 (with at least one staminodal member called the labellum, always being present. A specialized staminode, the stamen, bears pollen from a half-anther. A somewhat narrower'petal' is the pistil, connected down to a three-chambered ovary; the flowers are red, orange, or yellow or any combination of those colours, are aggregated in inflorescences that are spikes or panicles. Although gardeners enjoy these odd flowers, nature intended them to attract pollinators collecting nectar and pollen, such as bees, hummingbirds and bats; the pollination mechanism is conspicuously specialized. Pollen is shed on the style while still in the bud, in the species and early hybrids some is found on the stigma because of the high position of the anther, which means that they are self-pollinating.
Cultivars have a lower anther, rely on pollinators alighting on the labellum and touching first the terminal stigma, the pollen. The wild species grow to at least 2–3 m in height, but there is a wide variation in size among cultivated plants. Cannas grow from swollen underground stems known as rhizomes, which store starch, this is the main attraction of the plant to agriculture, having the largest starch particles of all plant life. Canna is the only member of the Liliopsida class in which hibernation of seed is known to occur, due to its hard, impenetrable seed covering. Canna indica called achira in Latin America, has been cultivated by Native Americans in tropical America for thousands of years and was one of the earliest domesticated plants in the Americas; the starchy root is edible. The first species of Canna introduced to Europe was C. indica L., imported from the East Indies, though the species originated from the Americas. Charles de l'Ecluse, who first described and sketched C. indica, indicated this origin, stated that it was given the name indica, not because the plant is from India, in Asia, but because this species was transported from America: Quia ex America primum delata sit.
Much in 1658, Willem Piso made reference to another species which he documented under the vulgar or common name of'Albara' and'Pacivira', which resided, he said, in the'shaded and damp places, between the tropics'. Without exception, all Canna species that have been introduced into Europe can be traced back to the Americas, it can be asserted with confidence that Canna is an American genus. If Asia and Africa provided some of the early introductions, they were only varieties resulting from C. indica and C. glauca cultivars that have been grown for a long time in India and Africa, with both species imported from Central and South America. Since cannas have hard and durable seed coverings, it is that seed remains would survive in the right conditions and been found by archaeologists in the Old World if Canna had been grown there from antiquity. If the soils of India or Africa had produced some of them, they would have been imported before the 1860s into European gardens. Although most cannas grown these days are cultivars, there are 20 known species of the wild form, in the last three decades of the 20th century, Canna species have been categorized by two different taxonomists, Paul Maas, from the Netherlands and Nobuyuki Tanaka from Japan.
Both reduced the number of species from the 50-100 accepted assigning most as synonyms. This reduction in species is confirmed by work done by Kress and Prince at the Smithsonian Institution. See List of Canna species for full species information and descriptions; the genus is native to tropical and subtropical regions of the New World, from the southern United States and south to northern Argentina. Canna indica has become naturalized in many tropical areas around the world, is a difficult plant to remove, is invasive in some places. C
Cucurbitaceae
The Cucurbitaceae called cucurbits and the gourd family, are a plant family consisting of about 965 species in around 95 genera, the most important of which are: Cucurbita – squash, zucchini, some gourds Lagenaria – calabash, others that are inedible Citrullus – watermelon and others Cucumis – cucumber, various melons Luffa – the common name is luffa, sometimes spelled loofah The plants in this family are grown around the tropics and in temperate areas, where those with edible fruits were among the earliest cultivated plants in both the Old and New Worlds. The Cucurbitaceae family ranks among the highest of plant families for number and percentage of species used as human food; the Cucurbitaceae consist of 98 proposed genera with 975 species in regions tropical and subtropical. All species are sensitive to frost. Most of the plants in this family are annual vines, but some are woody lianas, thorny shrubs, or trees. Many species have yellow or white flowers; the stems are pentangular. Tendrils are present at 90° to the leaf petioles at nodes.
Leaves are palmately compound. The flowers are unisexual, on the same plant; the female flowers have inferior ovaries. The fruit is a kind of modified berry called a pepo. One of the oldest fossil cucurbits so far is †Cucurbitaciphyllum lobatum from the Paleocene epoch, found at Shirley Canal, Montana, it was described for the first time in 1924 by the paleobotanist Frank Hall Knowlton. The fossil leaf is palmate, trilobed with an entire or serrate margin, it has a leaf pattern similar to the members of the genera Kedrostis and Zehneria. The most recent classification of Cucurbitaceae delineates 15 tribes: Modern molecular phylogenetics suggest the following relationships: Six cucurbit crops are represented in 23 Byzantine-era mosaics from Israel, these being round melons, sponge gourds, snake melons, adzhur melons, bottle gourds. Cucurbits are represented in 23 of the 134 mosaics containing images of crop plants, a high frequency of 17%. Several of the cucurbit images have not been found elsewhere, suggesting a diverse and developed local horticulture of cucurbits in Israel during the Byzantine era.
Representations of mature sponge gourds are found in widespread localities, suggestive of the high value accorded to cleanliness and hygiene. The name Cucurbitaceae comes to international scientific vocabulary from New Latin, from Cucurbita, the type genus, + -aceae, a standardized suffix for plant family names in modern taxonomy; the genus name comes from the Classical Latin word cucurbita, "gourd". Bates D, Robinson R, Jeffrey C, eds.. Biology and Utilization of the Cucurbitaceae. Cornell University Press. ISBN 978-0-8014-1670-5. Jeffrey C.. "A new system of Cucurbitaceae". Bot. Zhurn. 90: 332–335. Cucurbitaceae in T. C. Andres. Cucurbitaceae in L. Watson and M. J. Dallwitz; the families of flowering plants: descriptions, identification, information retrieval. Https://web.archive.org/web/20070103200438/http://delta-intkey.com/
Pollinium
A pollinium is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is seen in plants such as orchids and many species of milkweeds. Usage of the term differs: in some orchids two masses of pollen are well attached to one another, but in other orchids there are two halves each of, sometimes referred to as a pollinium. Most orchids have waxy pollinia; these are connected to one or two elongate stipes, which in turn are attached to a sticky viscidium, a disc-shaped structure that sticks to a visiting insect. Some orchid genera have mealy pollinia; these are tapering into a caudicle, attached to the viscidium. They extend into the middle section of the column; the pollinarium is a collective term that means either the complete set of pollinia from all the anthers of a flower, as in Asclepiadoideae, in Asclepiadoideae, a pair of pollinia and the parts that connect them, or in orchids, a pair of pollinia with two viscidia and the other connecting parts
Phyllanthus
Phyllanthus is the largest genus in the flowering plant family Phyllanthaceae. Estimates of the number of species in this genus vary from 750 to 1200. Phyllanthus has a remarkable diversity of growth forms including annual and perennial herbs, climbers, floating aquatics, pachycaulous succulents; some have flattened. It has a wide variety of floral morphologies and chromosome numbers and has one of the widest range of pollen types of any seed plant genus. Despite their variety all Phyllanthus species express a specific type of growth called "phyllanthoid branching" in which the vertical stems bear deciduous, plagiotropic stems; the leaves on the main axes are reduced to scales called "cataphylls", while leaves on the other axes develop normally. Phyllanthus is distributed in all subtropical regions on Earth; the circumscription of this genus has been a cause of much disagreement. Molecular phylogenetic studies have shown that Phyllanthus is paraphyletic over Reverchonia, Glochidion and Breynia.
A recent revision of the family Phyllanthaceae has subsumed all four of these genera into Phyllanthus. This enlarged version of Phyllanthus might be divided into smaller genera, including 32 Chinese species. Phyllanthus abnormis Baill. - Drummond's leafflower Phyllanthus acidus Skeels - Otaheite gooseberry Phyllanthus acuminatus Vahl - Jamaican gooseberry tree Phyllanthus amarus Schumacher Phyllanthus angustifolius Sw. Phyllanthus arbuscula J. F. Gmel. Phyllanthus axillaris Müll. Arg. Phyllanthus brasiliensis Poir. Phyllanthus caesiifolius Petra Hoffm. & Cheek Phyllanthus caroliniensis Walt. - native to the Americas Phyllanthus cauliflorus Griseb. Phyllanthus cladanthus Müll. Arg. Phyllanthus cochinchinensis Spreng. Phyllanthus cuneifolius. Phyllanthus emblica L. - Indian gooseberry known as amla or amalaki. Phyllanthus engleri Pax Phyllanthus epiphyllanthus. Phyllanthus eximius G. L. Webster & Proctor Phyllanthus fadyenii Urb. Phyllanthus fluitans - red root floater, sometimes sold in aquarium shops Phyllanthus fraternus G.
L. Webster Phyllanthus gentryi Webster Phyllanthus grandifolius L. Phyllanthus hakgalensis Phyllanthus juglandifolius Willd. Phyllanthus lacunarius F. Muell. Phyllanthus latifolius Sw. Phyllanthus liebmannianus Muell.-Arg. Phyllanthus maderaspatensis. Phyllanthus millei Standl. Phyllanthus mirabilis Müll. Arg. - the only succulent species of this genus Phyllanthus montanus Sw. Phyllanthus myrtifolius - Wight. Muell. Arg. Phyllanthus muellerianus Exell Phyllanthus niruri L. - Chanca piedra Phyllanthus nyale Petra Hoffm. & Cheek Phyllanthus parvifolius Buch.-Ham. Ex D. Don Phyllanthus pentaphyllus C. Wright ex Griseb. Phyllanthus phialanthoides Phyllanthus polygonoides Nutt. Ex Spreng. - Smartweed leafflower Phyllanthus polyspermus Shumach. & Thonn. - misidentified as P. reticulatus Phyllanthus profusus N. E. Br. Phyllanthus pulcher Wallich ex Muell.-Arg. Phyllanthus reticulatus Poir. - Asian sp. similar in appearance to P. polyspermus Phyllanthus revaughanii Coode Phyllanthus saffordii Merr. Phyllanthus salviifolius.
Arg. Phyllanthus societatis Müll. Arg. Phyllanthus sponiifolius Müll. Arg. Phyllanthus stipulatus G. L. Webster Phyllanthus taxodiifolius Beille Phyllanthus tenellus Roxb. Phyllanthus urinaria L. - chamberbitter Phyllanthus virgatus G. Forst. Phyllanthus warnockii G. L. Webster Phyllanthus watsonii A. Shaw Phyllanthus welwitschianus Müll. Arg. For full list, see List of Phyllanthus species. Two fossil seeds of a Phyllanthus species have been extracted from borehole samples of the Middle Miocene fresh water deposits in Nowy Sacz Basin, West Carpathians, Poland; the seeds are similar to seeds of the fossil species †Phyllanthus triquetra and †Phyllanthus compassica from the Oligocene and Miocene of West Siberia. Phyllanthus fossils are known from several Pliocene sites in Poland. Phyllanthus are of note in the fields of pollination biology and coevolution because some but not all species in the genus have a specialized mutualism with moths in the genus Epicephala, in which the moths pollinate the flowers.
While ensuring that the tree may produce viable seeds, the moths lay eggs in the flowers' ovaries where their larvae consume a subset of the developing seeds as nourishment. Other species of Epicephala are pollinators of certain species of plants in the genera Glochidion and Breynia, both of which are phylogenetically nested within Phyllanthus. For its content of tannins, P. emblica fruit has a history of use in traditional medicine and is under study for its potential biological properties. Leaves, stem and berries of this genus contain lignans and other phytochemicals. Phyllanthus species have been assessed for use in people with chronic hepatitis B virus infection, but the low quality of clinical trials has prevented any conclusion about efficacy as of 2013. Kathriarachchi, Hashendra. "Molecular phylogenetics of Phyllanthaceae inferred from five genes". Molecular Phylogenetics and Evolution. 36: 112–34. Doi:10.1016/j.ympev.2004.12.002. PMID 15904861. Pruesapan, K.. C.. "Delimitation of Sauropus Based on Plastid matK and Nuclear Ribosomal ITS DNA Sequence Data".
Annals of Botany. 102: 1007–18. Doi:10.1093/aob/mcn193. PMC
Orchidaceae
The Orchidaceae are a diverse and widespread family of flowering plants, with blooms that are colourful and fragrant known as the orchid family. Along with the Asteraceae, they are one of the two largest families of flowering plants; the Orchidaceae have about 28,000 accepted species, distributed in about 763 genera. The determination of which family is larger is still under debate, because verified data on the members of such enormous families are continually in flux. Regardless, the number of orchid species nearly equals the number of bony fishes and is more than twice the number of bird species, about four times the number of mammal species; the family encompasses about 6–11% of all seed plants. The largest genera are Bulbophyllum, Epidendrum and Pleurothallis, it includes Vanilla–the genus of the vanilla plant, the type genus Orchis, many cultivated plants such as Phalaenopsis and Cattleya. Moreover, since the introduction of tropical species into cultivation in the 19th century, horticulturists have produced more than 100,000 hybrids and cultivars.
Orchids are distinguished from other plants, as they share some evident, shared derived characteristics, or synapomorphies. Among these are: bilateral symmetry of the flower, many resupinate flowers, a nearly always modified petal, fused stamens and carpels, small seeds. All orchids are perennial herbs, they can grow according to two patterns: Monopodial: The stem grows from a single bud, leaves are added from the apex each year and the stem grows longer accordingly. The stem of orchids with a monopodial growth can reach several metres in length, as in Vanda and Vanilla. Sympodial: Sympodial orchids have a front and a back; the plant produces a series of adjacent shoots, which grow to a certain size and stop growing and are replaced. Sympodial orchids grow laterally following the surface of their support; the growth continues by development of new leads, with their own leaves and roots, sprouting from or next to those of the previous year, as in Cattleya. While a new lead is developing, the rhizome may start its growth again from a so-called'eye', an undeveloped bud, thereby branching.
Sympodial orchids may have visible pseudobulbs joined by a rhizome, which creeps along the top or just beneath the soil. Terrestrial orchids may form corms or tubers; the root caps of terrestrial orchids are white. Some sympodial terrestrial orchids, such as Orchis and Ophrys, have two subterranean tuberous roots. One is used as a food reserve for wintry periods, provides for the development of the other one, from which visible growth develops. In warm and humid climates, many terrestrial orchids do not need pseudobulbs. Epiphytic orchids, those that grow upon a support, have modified aerial roots that can sometimes be a few meters long. In the older parts of the roots, a modified spongy epidermis, called velamen, has the function of absorbing humidity, it can have a silvery-grey, white or brown appearance. In some orchids, the velamen includes spongy and fibrous bodies near the passage cells, called tilosomes; the cells of the root epidermis grow at a right angle to the axis of the root to allow them to get a firm grasp on their support.
Nutrients for epiphytic orchids come from mineral dust, organic detritus, animal droppings and other substances collecting among on their supporting surfaces. The base of the stem of sympodial epiphytes, or in some species the entire stem, may be thickened to form a pseudobulb that contains nutrients and water for drier periods; the pseudobulb has a smooth surface with lengthwise grooves, can have different shapes conical or oblong. Its size is variable; some Dendrobium species have long, canelike pseudobulbs with short, rounded leaves over the whole length. With ageing, the pseudobulb becomes dormant. At this stage, it is called a backbulb. Backbulbs still hold nutrition for the plant, but a pseudobulb takes over, exploiting the last reserves accumulated in the backbulb, which dies off, too. A pseudobulb lives for about five years. Orchids without noticeable pseudobulbs are said to have growths, an individual component of a sympodial plant. Like most monocots, orchids have simple leaves with parallel veins, although some Vanilloideae have reticulate venation.
Leaves may be ovate, lanceolate, or orbiculate, variable in size on the individual plant. Their characteristics are diagnostic, they are alternate on the stem folded lengthwise along the centre, have no stipules. Orchid leaves have siliceous bodies called stegmata in the vascular bundle sheaths and are fibrous; the structure of the leaves corresponds to the specific habitat of the plant. Species that bask in sunlight, or grow on sites which can be very dry, have thick, leathery leaves and the laminae are covered by a waxy cuticle to retain their necessary water supply. Shade-loving species, on the other hand, have thin leaves; the leaves of most orchids are perennial, that is, they live for several years, while others those with plicate leaves as in Catasetum, shed them annually and de
Ericaceae
The Ericaceae are a family of flowering plants known as the heath or heather family, found most in acid and infertile growing conditions. The family is large, with c. 4250 known species spread across 124 genera, making it the 14th most species-rich family of flowering plants. The many well-known and economically important members of the Ericaceae include the cranberry, huckleberry and various common heaths and heathers; the Ericaceae contain a morphologically diverse range of taxa, including herbs, dwarf shrubs and trees. Their leaves are alternate or whorled and without stipules, their flowers show considerable variability. The petals are fused with shapes ranging from narrowly tubular to funnelform or urn-shaped; the corollas are radially symmetrical and urn-shaped, but many flowers of the genus Rhododendron are somewhat bilaterally symmetrical. Anthers open by pores. Adanson used the term Vaccinia to describe a similar family, but Jussieu first used the term Ericaceae; the name comes from the type genus Erica.
The exact meaning is difficult to interpret, but some sources show it as meaning'heather'. The name may have been used informally to refer to the plants before Linnaean times, been formalised when Linnaeus described Erica in 1753, again when Jussieu described the Ericaceae in 1789; the Ericaceae included both subfamilies and tribes. In 1971, who outlined the history from 1876 and in some instances 1839, recognised six subfamilies, further subdivided four of the subfamilies into tribes, the Rhododendroideae having seven tribes. Within tribe Rhodoreae, five genera were described, Rhododendron L. Therorhodion Small, Ledum L. Tsusiophyllum Max. Menziesia J. E. Smith, that were transferred into Rhododendron, along with Diplarche from the monogeneric tribe Diplarcheae. In 2002, systematic research resulted in the inclusion of the recognised families Empetraceae, Monotropaceae and Pyrolaceae into the Ericaceae based on a combination of molecular, morphological and embryological data, analysed within a phylogenetic framework.
The move increased the morphological and geographical range found within the group. One possible classification of the resulting family includes 9 subfamilies, 126 genera, about 4000 species: Enkianthoideae Kron, Judd & Anderberg Pyroloideae Kosteltsky Monotropoideae Arnott Arbutoideae Niedenzu Cassiopoideae Kron & Judd Ericoideae Link Harrimanelloideae Kron & Judd Styphelioideae Sweet Vaccinioideae Arnott See the full list at List of Ericaceae genera; the Ericaceae have a nearly worldwide distribution. They are absent from continental Antarctica, parts of the high Arctic, central Greenland and central Australia, much of the lowland tropics and neotropics; the family is composed of plants that can tolerate acidic, infertile conditions. Like other stress-tolerant plants, many Ericaceae have mycorrhizal fungi to assist with extracting nutrients from infertile soils, as well as evergreen foliage to conserve absorbed nutrients; this trait is not found in the Clethraceae and Cyrillaceae, the two families most related to the Ericaceae.
Most Ericaceae form a distinctive accumulation of mycorrhizae, in which fungi grow in and around the roots and provide the plant with nutrients. The Pyroloideae are gain sugars from the mycorrhizae, as well as nutrients. In many parts of the world, a "heath" or "heathland" is an environment characterised by an open dwarf-shrub community found on low-quality acidic soils dominated by plants in the Ericaceae. A common example is Erica tetralix; this plant family is typical of peat bogs and blanket bogs. In eastern North America, members of this family grow in association with an oak canopy, in a habitat known as an oak-heath forest. In heathland, plants in the family Ericaceae serve as hostplants to Plebejus argus; some evidence suggests eutrophic rainwater can convert ericoid heaths with species such as Erica tetralix to grasslands. Nitrogen is suspect in this regard, may be causing measurable changes to the distribution and abundance of some ericaceous species. Stevens, P. F.. "A classification of the Ericaceae: subfamilies and tribes".
Botanical Journal of the Linnean Society. 64: 1–53. Doi:10.1111/j.1095-8339.1971.tb02133.x. Cafferty, Steve. "Typification of Linnaean Plant Names in Ericaceae". Taxon. 51: 751–753. Doi:10.2307/1555030. JSTOR 10.2307/1555030. Stevens, P. F.. G. H.. L.. A.. K.. S.. J.. B.. S.. M.. M.. "Ericaceae". In Kubitzki, K. Flowering Plants. Dicotyledons: Celastrales, Rosales, Ericales; the families and genera of vascular plants. 6. Springer. Pp. 145–194. ISBN 9783540065128. Ericaceae at The Plant List Ericaceae, Empetraceae, Monotr
.jpg)
Rendle, Alfred Barton (1911). . In Chisholm, Hugh (ed.). Encyclopædia Britannica. 10 (11th ed.). Cambridge University Press. pp. 553–573.
Rendle, Alfred Barton (1911). 
