Algae
Algae is an informal term for a large, diverse group of photosynthetic eukaryotic organisms that are not closely related, is thus polyphyletic. Including organisms ranging from unicellular microalgae genera, such as Chlorella and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 m in length. Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomata and phloem, which are found in land plants; the largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example and the stoneworts. No definition of algae is accepted. One definition is that algae "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells". Although cyanobacteria are referred to as "blue-green algae", most authorities exclude all prokaryotes from the definition of algae.
Algae constitute a polyphyletic group since they do not include a common ancestor, although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga. Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction. Algae lack the various structures that characterize land plants, such as the phyllids of bryophytes, rhizoids in nonvascular plants, the roots and other organs found in tracheophytes. Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy; some unicellular species of green algae, many golden algae, euglenids and other algae have become heterotrophs, sometimes parasitic, relying on external energy sources and have limited or no photosynthetic apparatus.
Some other heterotrophic organisms, such as the apicomplexans, are derived from cells whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago. The singular alga retains that meaning in English; the etymology is obscure. Although some speculate that it is related to Latin algēre, "be cold", no reason is known to associate seaweed with temperature. A more source is alliga, "binding, entwining"; the Ancient Greek word for seaweed was φῦκος, which could mean either the seaweed or a red dye derived from it. The Latinization, fūcus, meant the cosmetic rouge; the etymology is uncertain, but a strong candidate has long been some word related to the Biblical פוך, "paint", a cosmetic eye-shadow used by the ancient Egyptians and other inhabitants of the eastern Mediterranean.
It could be any color: black, green, or blue. Accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used; the name Fucus appears in a number of taxa. The algae contain chloroplasts. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events; the table below describes the composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members; some retain plastids, but not chloroplasts. Phylogeny based on plastid not nucleocytoplasmic genealogy: Linnaeus, in Species Plantarum, the starting point for modern botanical nomenclature, recognized 14 genera of algae, of which only four are considered among algae.
In Systema Naturae, Linnaeus described the genera Volvox and Corallina, a species of Acetabularia, among the animals. In 1768, Samuel Gottlieb Gmelin published the Historia Fucorum, the first work dedicated to marine algae and the first book on marine biology to use the new binomial nomenclature of Linnaeus, it included elaborate illustrations of seaweed and marine algae on folded leaves. W. H. Harvey and Lamouroux were the first to divide macroscopic algae into four divisions based on their pigmentation; this is the first use of a biochemical criterion in plant systematics. Harvey's four divisions are: red algae, brown algae, green algae, Diatomaceae. At this time, microscopic algae were discovered and reported by a different group of workers studying the Infusoria. Unlike macroalgae, which were viewed as plants, microalgae were considered animals because they are motile; the nonmotile microalgae were sometimes seen as stages of the lifecycle of plants, macroalgae, or animals. Although used as a taxonomic category in some pre-D
Bryophyte
Bryophytes are an informal group consisting of three divisions of non-vascular land plants: the liverworts and mosses. They are characteristically limited in size and prefer moist habitats although they can survive in drier environments; the bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures, they reproduce via spores. Bryophytes are considered to be a paraphyletic group and not a monophyletic group, although some studies have produced contrary results. Regardless of their status, the name is convenient and remains in use as an informal collective term; the term "bryophyte" comes from Greek βρύον, bryon "tree-moss, oyster-green" and φυτόν, phyton "plant". The defining features of bryophytes are: Their life cycles are dominated by the gametophyte stage Their sporophytes are unbranched They do not have a true vascular tissue containing lignin Bryophytes exist in a wide variety of habitats, they can be found growing in a range of temperatures and moisture.
Bryophytes can grow where vascularized plants cannot because they do not depend on roots for an uptake of nutrients from soil. Bryophytes can survive on bare soil. Like all land plants, bryophytes have life cycles with alternation of generations. In each cycle, a haploid gametophyte, each of whose cells contains a fixed number of unpaired chromosomes, alternates with a diploid sporophyte, whose cell contain two sets of paired chromosomes. Gametophytes produce haploid sperm and eggs which fuse to form diploid zygotes that grow into sporophytes. Sporophytes produce haploid spores by meiosis. Bryophytes are gametophyte dominant, meaning that the more prominent, longer-lived plant is the haploid gametophyte; the diploid sporophytes appear only and remain attached to and nutritionally dependent on the gametophyte. In bryophytes, the sporophytes produce a single sporangium. Liverworts and hornworts spend most of their lives as gametophytes. Gametangia and antheridia, are produced on the gametophytes, sometimes at the tips of shoots, in the axils of leaves or hidden under thalli.
Some bryophytes, such as the liverwort Marchantia, create elaborate structures to bear the gametangia that are called gametangiophores. Sperm are flagellated and must swim from the antheridia that produce them to archegonia which may be on a different plant. Arthropods can assist in transfer of sperm. Fertilized eggs become zygotes. Mature sporophytes remain attached to the gametophyte, they consist of a stalk called a single sporangium or capsule. Inside the sporangium, haploid spores are produced by meiosis; these are dispersed, most by wind, if they land in a suitable environment can develop into a new gametophyte. Thus bryophytes disperse by a combination of swimming sperm and spores, in a manner similar to lycophytes and other cryptogams; the arrangement of antheridia and archegonia on an individual bryophyte plant is constant within a species, although in some species it may depend on environmental conditions. The main division is between species in which the antheridia and archegonia occur on the same plant and those in which they occur on different plants.
The term monoicous may be used where antheridia and archegonia occur on the same gametophyte and the term dioicous where they occur on different gametophytes. In seed plants, "monoecious" is used where flowers with anthers and flowers with ovules occur on the same sporophyte and "dioecious" where they occur on different sporophytes; these terms may be used instead of "monoicous" and "dioicous" to describe bryophyte gametophytes. "Monoecious" and "monoicous" are both derived from the Greek for "one house", "dioecious" and "dioicous" from the Greek for two houses. The use of the "oicy" terminology is said to have the advantage of emphasizing the difference between the gametophyte sexuality of bryophytes and the sporophyte sexuality of seed plants. Monoicous plants are hermaphroditic, meaning that the same plant has both sexes; the exact arrangement of the antheridia and archegonia in monoicous plants varies. They may be borne on different shoots, on the same shoot but not together in a common structure, or together in a common "inflorescence".
Dioicous plants are unisexual. All four patterns occur in species of the moss genus Bryum. Traditionally, all living land plants without vascular tissues were classified in a single taxonomic group a division. More phylogenetic research has questioned whether the bryophytes form a monophyletic group and thus whether they should form a single taxon. Although a 2005 study supported the traditional view that the bryophytes form a monophyletic group, by 2010 a broad consensus had emerged among systematists that bryophytes as a whole are not a natural group, although each of the three extant groups is monophyletic; the three bryophyte clades are the Marchantiophyta and Anthocerotophyta. The vascular plants or tracheophytes form a fourth, unranked clade of land plants called the "Polysporangiophyta". In this analysis, hornworts are sister
Fern
A fern is a member of a group of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e. having specialized tissues that conduct water and nutrients and in having life cycles in which the sporophyte is the dominant phase. Like other vascular plants, ferns have complex leaves called megaphylls, that are more complex than the microphylls of clubmosses. Most ferns are leptosporangiate ferns, sometimes referred to as true ferns, they produce coiled fiddleheads that expand into fronds. The group includes about 10,560 known extant species. Ferns are defined here in the broad sense, being all of the Polypodiopsida, comprising both the leptosporangiate and eusporangiate ferns, the latter itself comprising ferns other than those denominated true ferns, including horsetails or scouring rushes, whisk ferns, marattioid ferns, ophioglossoid ferns. Ferns first appear in the fossil record about 360 million years ago in the late Devonian period, but many of the current families and species did not appear until 145 million years ago in the early Cretaceous, after flowering plants came to dominate many environments.
The fern Osmunda claytoniana is a paramount example of evolutionary stasis. Ferns are not of major economic importance, but some are used for food, medicine, as biofertilizer, as ornamental plants and for remediating contaminated soil, they have been the subject of research for their ability to remove some chemical pollutants from the atmosphere. Some fern species, such as bracken and water fern are significant weeds world wide; some fern genera, such as Azolla can fix nitrogen and make a significant input to the nitrogen nutrition of rice paddies. They play certain roles in mythology and art. Like the sporophytes of seed plants, those of ferns consist of stems and roots. Stems: Fern stems are referred to as rhizomes though they grow underground only in some of the species. Epiphytic species and many of the terrestrial ones have above-ground creeping stolons, many groups have above-ground erect semi-woody trunks; these can reach up to 20 meters tall in a few species. Leaf: The green, photosynthetic part of the plant is technically a megaphyll and in ferns, it is referred to as a frond.
New leaves expand by the unrolling of a tight spiral called a crozier or fiddlehead fern. This uncurling of the leaf is termed circinate vernation. Leaves are divided into a sporophyll. A trophophyll frond is a vegetative leaf analogous to the typical green leaves of seed plants that does not produce spores, instead only producing sugars by photosynthesis. A sporophyll frond is a fertile leaf that produces spores borne in sporangia that are clustered to form sori. In most ferns, fertile leaves are morphologically similar to the sterile ones, they photosynthesize in the same way. In some groups, the fertile leaves are much narrower than the sterile leaves, may have no green tissue at all; the anatomy of fern leaves can either be simple or divided. In tree ferns, the main stalk that connects the leaf to the stem has multiple leaflets; the leafy structures that grow from the stipe are known as pinnae and are again divided into smaller pinnules. Roots: The underground non-photosynthetic structures that take up water and nutrients from soil.
They are always fibrous and structurally are similar to the roots of seed plants. Like all other vascular plants, the diploid sporophyte is the dominant phase or generation in the life cycle; the gametophytes of ferns, are different from those of seed plants. They are free-living and resemble liverworts, whereas those of seed plants develop within the spore wall and are dependent on the parent sporophyte for their nutrition. A fern gametophyte consists of: Prothallus: A green, photosynthetic structure, one cell thick heart or kidney shaped, 3–10 mm long and 2–8 mm broad; the prothallus produces gametes by means of: Antheridia: Small spherical structures that produce flagellate sperm. Archegonia: A flask-shaped structure that produces a single egg at the bottom, reached by the sperm by swimming down the neck. Rhizoids: root-like structures that consist of single elongated cells, that absorb water and mineral salts over the whole structure. Rhizoids anchor the prothallus to the soil. Ferns first appear in the fossil record in the early Carboniferous period.
By the Triassic, the first evidence of ferns related to several modern families appeared. The great fern radiation occurred in the late Cretaceous, when many modern families of ferns first appeared. Ferns were traditionally classified in the class Filices, in a Division of the Plant Kingdom named Pteridophyta or Filicophyta. Pteridophyta is no longer recognised as a valid taxon; the ferns are referred to as Polypodiophyta or, when treated as a subdivision of Tracheophyta, although this name sometimes only refers to leptosporangiate ferns. Traditionally, all of the spore producing vascular plants were informally denominated the pteridophytes, rendering the term synonymous with ferns and fern allies; this can be confusing because members of the division Pteridophyta were denominated pteridophytes. Traditionally, three discrete groups have be
Phytochemistry
Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. Those studying phytochemistry strive to describe the structures of the large number of secondary metabolic compounds found in plants, the functions of these compounds in human and plant biology, the biosynthesis of these compounds. Plants synthesize phytochemicals for many reasons, including to protect themselves against insect attacks and plant diseases. Phytochemicals in food plants are active in human biology, in many cases have health benefits; the compounds found in plants are of many kinds, but most are in four major biochemical classes, the alkaloids, glycosides and terpenes. Phytochemistry can be considered sub-fields of chemistry. Activities can be led in the wild with the aid of ethnobotany; the applications of the discipline can be for pharmacognosy, or the discovery of new drugs, or as an aid for plant physiology studies. Techniques used in the field of phytochemistry are extraction and structural elucidation of natural products, as well as various chromatography techniques.
The list of simple elements of which plants are constructed—carbon, hydrogen, phosphorus, etc.—is not different from similar lists for animals, fungi, or bacteria. The fundamental atomic components of plants are the same as for all life. Phytochemistry is used in the field of Chinese medicine in the field of herbal medicine. Phytochemical technique applies to the quality control of Chinese medicine, Ayurvedic medicine or herbal medicine of various chemical components, such as saponins, volatile oils and anthraquinones. In the development of rapid and reproducible analytical techniques, the combination of HPLC with different detectors, such as diode array detector, refractive index detector, evaporative light scattering detector and mass spectrometric detector, has been developed. In most cases, biologically active compounds in Chinese medicine, Ayurveda, or herbal medicine have not been determined. Therefore, it is important to use the phytochemical methods to screen and analyze bioactive components, not only for the quality control of crude drugs, but for the elucidation of their therapeutic mechanisms.
Modern pharmacological studies indicate that binding to receptors or ion channels on cell membranes is the first step of some drug actions. A new method in phytochemistry called biochromatography has been developed; this method combines human red cell membrane extraction and high performance liquid chromatography to screen potential active components in Chinese medicine. Many plants produce chemical compounds for defence against herbivores; these are useful as drugs, the content and known pharmacological activity of these substances in medicinal plants is the scientific basis for their use. The major classes of pharmacologically active phytochemicals are described below, with examples of medicinal plants that contain them. Human settlements are surrounded by weeds useful as medicines, such as nettle and chickweed. Many phytochemicals, including curcumin, epigallocatechin gallate and resveratrol are pan-assay interference compounds and are not useful in drug discovery. Alkaloids are bitter-tasting chemicals widespread in nature, toxic.
There are several classes with different modes of action as drugs, both recreational and pharmaceutical. Medicines of different classes include atropine and hyoscyamine, the traditional medicine berberine, cocaine, morphine, reserpine and quinine, vincristine. Anthraquinone glycosides are found in the laxatives senna and Aloe; the cardiac glycosides are powerful drugs from plants including lily of the valley. They include digoxin and digitoxin which support the beating of the heart, act as diuretics. Polyphenols of several classes are widespread in plants, they include the colourful anthocyanins, hormone-mimicking phytoestrogens, astringent tannins. In Ayurveda, the astringent rind of the pomegranate is used as a medicine, while polyphenol extracts from plant materials such as grape seeds are sold for their potential health benefits They have been continually studied in cell cultures for their different anti-cancer effects. Plants containing phytoestrogens have been used for centuries to treat gynaecological disorders such as fertility and menopausal problems.
Among these plants are Pueraria mirifica, angelica and anise. Terpenes and terpenoids of many kinds are found in resinous plants such as the conifers, they are aromatic and serve to repel herbivores. Their scent makes them useful in essential oils, whether for perfumes such as rose and lavender, or for aromatherapy; some have had medicinal uses: thymol is an antiseptic and was once used as a vermifuge. Tropical Botanical Garden and Research Institute UBC Botanical Garden and Centre for Plant Research
Stoma
In botany, a stoma called a stomate, is a pore, found in the epidermis of leaves and other organs, that facilitates gas exchange. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the stomatal opening; the term is used collectively to refer to the entire stomatal complex, consisting of the paired guard cells and the pore itself, referred to as the stomatal aperture. Air enters the plant through these openings by gaseous diffusion, contains carbon dioxide and oxygen, which are used in photosynthesis and respiration, respectively. Oxygen produced as a by-product of photosynthesis diffuses out to the atmosphere through these same openings. Water vapor diffuses through the stomata into the atmosphere in a process called transpiration. Stomata are present in the sporophyte generation of all land plant groups except liverworts. In vascular plants the number and distribution of stomata varies widely. Dicotyledons have more stomata on the lower surface of the leaves than the upper surface.
Monocotyledons such as onion and maize may have about the same number of stomata on both leaf surfaces. In plants with floating leaves, stomata may be found only on the upper epidermis and submerged leaves may lack stomata entirely. Most tree species have stomata only on the lower leaf surface. Leaves with stomata on both the upper and lower leaf are called. Size varies across species, with end-to-end lengths ranging from 10 to 80 µm and width ranging from a few to 50 µm. Carbon dioxide, a key reactant in photosynthesis, is present in the atmosphere at a concentration of about 400 ppm. Most plants require the stomata to be open during daytime; the air spaces in the leaf are saturated with water vapour, which exits the leaf through the stomata. Therefore, plants cannot gain carbon dioxide without losing water vapour. Ordinarily, carbon dioxide is fixed to ribulose-1,5-bisphosphate by the enzyme RuBisCO in mesophyll cells exposed directly to the air spaces inside the leaf; this exacerbates the transpiration problem for two reasons: first, RuBisCo has a low affinity for carbon dioxide, second, it fixes oxygen to RuBP, wasting energy and carbon in a process called photorespiration.
For both of these reasons, RuBisCo needs high carbon dioxide concentrations, which means wide stomatal apertures and, as a consequence, high water loss. Narrower stomatal apertures can be used in conjunction with an intermediary molecule with a high carbon dioxide affinity, PEPcase. Retrieving the products of carbon fixation from PEPCase is an energy-intensive process, however; as a result, the PEPCase alternative is preferable only where water is limiting but light is plentiful, or where high temperatures increase the solubility of oxygen relative to that of carbon dioxide, magnifying RuBisCo's oxygenation problem. A group of desert plants called "CAM" plants open their stomata at night, use PEPcarboxylase to fix carbon dioxide and store the products in large vacuoles; the following day, they close their stomata and release the carbon dioxide fixed the previous night into the presence of RuBisCO. This saturates RuBisCO with carbon dioxide; this approach, however, is limited by the capacity to store fixed carbon in the vacuoles, so it is preferable only when water is limited.
However, most plants do not have the aforementioned facility and must therefore open and close their stomata during the daytime, in response to changing conditions, such as light intensity and carbon dioxide concentration. It is not certain how these responses work. However, the basic mechanism involves regulation of osmotic pressure; when conditions are conducive to stomatal opening, a proton pump drives protons from the guard cells. This means that the cells' electrical potential becomes negative; the negative potential opens potassium voltage-gated channels and so an uptake of potassium ions occurs. To maintain this internal negative voltage so that entry of potassium ions does not stop, negative ions balance the influx of potassium. In some cases, chloride ions enter, while in other plants the organic ion malate is produced in guard cells; this increase in solute concentration lowers the water potential inside the cell, which results in the diffusion of water into the cell through osmosis.
This increases the cell's turgor pressure. Because of rings of cellulose microfibrils that prevent the width of the guard cells from swelling, thus only allow the extra turgor pressure to elongate the guard cells, whose ends are held in place by surrounding epidermal cells, the two guard cells lengthen by bowing apart from one another, creating an open pore through which gas can move; when the roots begin to sense a water shortage in the soil, abscisic acid is released. ABA binds to receptor proteins in the guard cells' plasma membrane and cytosol, which first raises the pH of the cytosol of the cells and cause the concentration of free Ca2+ to increase in the cytosol due to influx from outside the cell and release of Ca2+ from internal stores such as the endoplasmic reticulum and vacuoles; this caus
Marchantiophyta
The Marchantiophyta are a division of non-vascular land plants referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information, it is estimated. Some of the more familiar species grow as a flattened leafless thallus, but most species are leafy with a form much like a flattened moss. Leafy species can be distinguished from the similar mosses on the basis of a number of features, including their single-celled rhizoids. Leafy liverworts differ from most mosses in that their leaves never have a costa and may bear marginal cilia. Other differences are not universal for all mosses and liverworts, but the occurrence of leaves arranged in three ranks, the presence of deep lobes or segmented leaves, or a lack of differentiated stem and leaves all point to the plant being a liverwort. Liverworts are small from 2–20 mm wide with individual plants less than 10 cm long, are therefore overlooked.
However, certain species may cover large patches of ground, trees or any other reasonably firm substrate on which they occur. They are distributed globally in every available habitat, most in humid locations although there are desert and Arctic species as well; some species can be a weed in gardens. Most liverworts are small, measuring from 2–20 millimetres wide with individual plants less than 10 centimetres long, so they are overlooked; the most familiar liverworts consist of a prostrate, ribbon-like or branching structure called a thallus. However, most liverworts produce flattened stems with overlapping scales or leaves in two or more ranks, the middle rank is conspicuously different from the outer ranks. Liverworts can most reliably be distinguished from the similar mosses by their single-celled rhizoids. Other differences are not universal for all mosses and all liverworts. Unlike any other embryophytes, most liverworts contain unique membrane-bound oil bodies containing isoprenoids in at least some of their cells, lipid droplets in the cytoplasm of all other plants being unenclosed.
The overall physical similarity of some mosses and leafy liverworts means that confirmation of the identification of some groups can be performed with certainty only with the aid of microscopy or an experienced bryologist. Liverworts have a gametophyte-dominant life cycle, with the sporophyte dependent on the gametophyte. Cells in a typical liverwort plant each contain only a single set of genetic information, so the plant's cells are haploid for the majority of its life cycle; this contrasts with the pattern exhibited by nearly all animals and by most other plants. In the more familiar seed plants, the haploid generation is represented only by the tiny pollen and the ovule, while the diploid generation is the familiar tree or other plant. Another unusual feature of the liverwort life cycle is that sporophytes are short-lived, withering away not long after releasing spores. In other bryophytes, the sporophyte is persistent and disperses spores over an extended period; the life of a liverwort starts from the germination of a haploid spore to produce a protonema, either a mass of thread-like filaments or else a flattened thallus.
The protonema is a transitory stage in the life of a liverwort, from which will grow the mature gametophore plant that produces the sex organs. The male organs produce the sperm cells. Clusters of antheridia are enclosed by a protective layer of cells called the perigonium; as in other land plants, the female organs are known as archegonia and are protected by the thin surrounding perichaetum. Each archegonium has a slender hollow tube, the "neck", down which the sperm swim to reach the egg cell. Liverwort species may be either monoicous. In dioicous liverworts and male sex organs are borne on different and separate gametophyte plants. In monoicous liverworts, the two kinds of reproductive structures are borne on different branches of the same plant. In either case, the sperm must move from the antheridia where they are produced to the archegonium where the eggs are held; the sperm of liverworts is biflagellate, i.e. they have two tail-like flagellae that enable them to swim short distances, provided that at least a thin film of water is present.
Their journey may be assisted by the splashing of raindrops. In 2008, Japanese researchers discovered that some liverworts are able to fire sperm-containing water up to 15 cm in the air, enabling them to fertilize female plants growing more than a metre from the nearest male; when sperm reach the archegonia, fertilisation occurs, leading to the production of a diploid sporophyte. After fertilisation, the immature sporophyte within the archegonium develops three distinct regions: a foot, which both anchors the sporophyte in place and receives nutrients from its "mother" plant, a spherical or ellipsoidal capsule, inside which the spores will be produced for dispersing to new locations, a seta which lies between the other two
Plant anatomy
Plant anatomy or phytotomy is the general term for the study of the internal structure of plants. It included plant morphology, the description of the physical form and external structure of plants, but since the mid-20th century plant anatomy has been considered a separate field referring only to internal plant structure. Plant anatomy is now investigated at the cellular level, involves the sectioning of tissues and microscopy. Although some plant anatomy studies utilize a systems approach, such as the study of vascular tissues, plant anatomy is more classically divided into the following structural categories: Flower anatomy Calyx Corolla Androecium Gynoecium Leaf anatomy Epidermis Palisade cells Stem anatomy Stem structure Fruit/Seed anatomy Ovule Seed structure Pericarp Accessory fruit Wood anatomy Bark Cork Phloem Vascular cambium Heartwood and sapwood branch collar Root anatomy Root structure About 300 BC Theophrastus wrote a number of plant treatises, only two of which survive, Enquiry into Plants, On the Causes of Plants.
He developed concepts of plant morphology and classification, which did not withstand the scientific scrutiny of the Renaissance. A Swiss physician and botanist, Gaspard Bauhin, introduced binomial nomenclature into plant taxonomy, he published Pinax theatri botanici in 1596, the first to use this convention for naming of species. His criteria for classification included natural relationships, or'affinities', which in many cases were structural, it was in the late 1600s. Italian doctor and microscopist, Marcello Malpighi, was one of the two founders of plant anatomy. In 1671 he published his Anatomia Plantarum, the first major advance in plant physiogamy since Aristotle; the other founder was the British doctor Nehemiah Grew. He published An Idea of a Philosophical History of Plants in 1672 and The Anatomy of Plants in 1682. Grew is credited with the recognition of plant cells, although he called them'vesicles' and'bladders', he identified and described the sexual organs of plants and their parts.
In the eighteenth century, Carl Linnaeus established taxonomy based on structure, his early work was with plant anatomy. While the exact structural level, to be considered to be scientifically valid for comparison and differentiation has changed with the growth of knowledge, the basic principles were established by Linnaeus, he published his master work, Species Plantarum in 1753. In 1802, French botanist Charles-François Brisseau de Mirbel, published Traité d'anatomie et de physiologie végétale establishing the beginnings of the science of plant cytology. In 1812, Johann Jacob Paul Moldenhawer published Beyträge zur Anatomie der Pflanzen, describing microscopic studies of plant tissues. In 1813 a Swiss botanist, Augustin Pyrame de Candolle, published Théorie élémentaire de la botanique, in which he argued that plant anatomy, not physiology, ought to be the sole basis for plant classification. Using a scientific basis, he established structural criteria for defining and separating plant genera.
In 1830, Franz Meyen published the first comprehensive review of plant anatomy. In 1838 German botanist Matthias Jakob Schleiden, published Contributions to Phytogenesis, stating, "the lower plants all consist of one cell, while the higher plants are composed of individual cells" thus confirming and continuing Mirbel's work. A German-Polish botanist, Eduard Strasburger, described the mitotic process in plant cells and further demonstrated that new cell nuclei can only arise from the division of other pre-existing nuclei, his Studien über Protoplasma was published in 1876. Gottlieb Haberlandt, a German botanist, studied plant physiology and classified plant tissue based upon function. On this basis, in 1884 he published Physiologische Pflanzenanatomie in which he described twelve types of tissue systems. British paleobotanists Dunkinfield Henry Scott and William Crawford Williamson described the structures of fossilized plants at the end of the nineteenth century. Scott's Studies in Fossil Botany was published in 1900.
Following Charles Darwin's Origin of Species a Canadian botanist, Edward Charles Jeffrey, studying the comparative anatomy and phylogeny of different vascular plant groups, applied the theory to plants using the form and structure of plants to establish a number of evolutionary lines. He published his The Anatomy of Woody Plants in 1917; the growth of comparative plant anatomy was spearheaded by British botanist Agnes Arber. She published Water Plants: A Study of Aquatic Angiosperms in 1920, Monocotyledons: A Morphological Study in 1925, The Gramineae: A Study of Cereal and Grass in 1934. Following World War II, Katherine Esau published, Plant Anatomy, which became the definitive textbook on plant structure in North American universities and elsewhere, it was still in print as of 2006, she followed up with her Anatomy of seed plants in 1960. Plant morphology Plant physiology Eames, Arthur Johnson. An Introduction to Plant Anatomy 2nd ed. McGraw-Hill, New York, link. Esau, Katherine. Plant Anatomy 2nd ed. Wiley, New York.
Meicenheimer, R. History of Plant Anatomy. Miami University, link. Cutler, D. F.. Anatomy of the Monocotyledons. 10 vols. Oxford University Press. Goffinet, B.. Morphology and classification of the Bryophyta. In: Goffinet, B.. Bryophyte Biology, 2nd ed. Cambridge University Press, pp. 55-138. Jeffrey, E. C.. The anatomy of w
