Parenchyma is the bulk of a substance. In animals, a parenchyma comprises the parts of an organ. The term parenchyma is New Latin, f, greek παρέγχυμα - parenkhuma, visceral flesh, f. παρεγχεῖν - parenkhein, to pour in f. para-, beside + en-, in + khein, the parenchyma is the functional parts of an organ in the body. This is in contrast to the stroma, which refers to the tissue of organs, namely. In the brain, the parenchyma refers to the tissue in the brain that is made up of the two types of brain cell and glial cells. Damage or trauma to the brain parenchyma often results in a loss of ability or even death. Lung parenchyma is the substance of the lung outside of the system that is involved with gas exchange and includes the alveoli. In cancer, the parenchyma refers to The portion of a tissue that lies outside the system and is often responsible for carrying out the specialized functions of the tissue. In plants, parenchyma is one of the three types of ground tissue, and the most common. It can be distinguished through their cell wall as compared to other cells.
Parenchyma cells make up the bulk of the parts of plants, including the insides of leaves, flowers
Chloroplasts /ˈklɔːrəˌplæsts, -plɑːsts/ are organelles, specialized subunits, in plant and algal cells. Their discovery inside plant cells is usually credited to Julius von Sachs and they use the ATP and NADPH to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of functions, including fatty acid synthesis, much amino acid synthesis. The number of chloroplasts per cell varies from one, in algae, up to 100 in plants like Arabidopsis. A chloroplast is a type of known as a plastid. Other plastid types, such as the leucoplast and the chromoplast, contain little chlorophyll, chloroplasts are highly dynamic—they circulate and are moved around within plant cells, and occasionally pinch in two to reproduce. Their behavior is influenced by environmental factors like light color. Chloroplasts, like mitochondria, contain their own DNA, which is thought to be inherited from their ancestor—a photosynthetic cyanobacterium that was engulfed by a eukaryotic cell.
Chloroplasts cannot be made by the plant cell and must be inherited by each cell during cell division. With one exception, all chloroplasts can probably be traced back to a single endosymbiotic event, despite this, chloroplasts can be found in an extremely wide set of organisms, some not even directly related to each other—a consequence of many secondary and even tertiary endosymbiotic events. The word chloroplast is derived from the Greek words chloros, which means green, and plastes, the first definitive description of a chloroplast was given by Hugo von Mohl in 1837 as discrete bodies within the green plant cell. In 1883, A. F. W. Schimper would name these bodies as chloroplastids, in 1884, Eduard Strasburger adopted the term chloroplasts. Chloroplasts are one of many types of organelles in the plant cell and they are considered to have originated from cyanobacteria through endosymbiosis—when a eukaryotic cell engulfed a photosynthesizing cyanobacterium that became a permanent resident in the cell.
Mitochondria are thought to have come from an event, where an aerobic prokaryote was engulfed. This origin of chloroplasts was first suggested by the Russian biologist Konstantin Mereschkowski in 1905 after Andreas Schimper observed in 1883 that chloroplasts closely resemble cyanobacteria, chloroplasts are only found in plants and the amoeboid Paulinella chromatophora. Cyanobacteria are considered the ancestors of chloroplasts and they are sometimes called blue-green algae even though they are prokaryotes. They are a phylum of bacteria capable of carrying out photosynthesis. Cyanobacteria contain a cell wall, which is thicker than in other gram-negative bacteria
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. Roots can be aerial or aerating, that is growing up above the ground or especially above water, furthermore, a stem normally occurring below ground is not exceptional either. Therefore, the root is best defined as the non-leaf, non-nodes bearing parts of the plants body, important internal structural differences between stems and roots exist. The fossil record of roots – or rather, infilled voids where roots rotted after death – spans back to the late Silurian and their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows. They can be discriminated using a range of features, the first root that comes from a plant is called the radicle. In response to the concentration of nutrients, roots synthesise cytokinin, Roots often function in storage of food and nutrients. The roots of most vascular plant species enter into symbiosis with fungi to form mycorrhizae.
In its simplest form, the root architecture refers to the spatial configuration of a plant’s root system. This system can be complex and is dependent upon multiple factors such as the species of the plant itself, the composition of the soil. The configuration of root systems serves to support the plant, compete with other plants. Roots grow to specific conditions, which, if changed, can impede a plants growth. For example, a system that has developed in dry soil may not be as efficient in flooded soil, yet plants are able to adapt to other changes in the environment. Root architecture plays the important role of providing a supply of nutrients and water as well as anchorage. The main terms used to classify the architecture of a system are, Branch magnitude. Root angle, the angle of a lateral root’s base around the parent root’s circumference, the angle of a lateral root from its parent root. Link radius, the diameter of a root, all components of the root architecture are regulated through a complex interaction between genetic responses and responses due to environmental stimuli.
These developmental stimuli are categorised as intrinsic, the genetic and nutritional influences, or extrinsic, the main hormones and respective pathways responsible for root architecture development include, Auxin – Auxin promotes root initiation, root emergence and primary root elongation. Cytokinins – Cytokinins regulate root apical meristem size and promote lateral root elongation, gibberellins – Together with ethylene they promote crown primordia growth and elongation
Botany, called plant science, plant biology or phytology, is the science of plant life and a branch of biology. A botanist or plant scientist is a scientist who specialises in this field, the term botany comes from the Ancient Greek word βοτάνη meaning pasture, grass, or fodder, βοτάνη is in turn derived from βόσκειν, to feed or to graze. Nowadays, botanists study approximately 410,000 species of plants of which some 391,000 species are vascular plants. Medieval physic gardens, often attached to monasteries, contained plants of medical importance and they were forerunners of the first botanical gardens attached to universities, founded from the 1540s onwards. One of the earliest was the Padua botanical garden and these gardens facilitated the academic study of plants. Efforts to catalogue and describe their collections were the beginnings of plant taxonomy, in the last two decades of the 20th century, botanists exploited the techniques of molecular genetic analysis, including genomics and proteomics and DNA sequences to classify plants more accurately.
Modern botany is a broad, multidisciplinary subject with inputs from most other areas of science, dominant themes in 21st century plant science are molecular genetics and epigenetics, which are the mechanisms and control of gene expression during differentiation of plant cells and tissues. Botany originated as herbalism, the study and use of plants for their medicinal properties, many records of the Holocene period date early botanical knowledge as far back as 10,000 years ago. This early unrecorded knowledge of plants was discovered in ancient sites of human occupation within Tennessee, the early recorded history of botany includes many ancient writings and plant classifications. Examples of early works have been found in ancient texts from India dating back to before 1100 BC, in archaic Avestan writings. His major works, Enquiry into Plants and On the Causes of Plants, constitute the most important contributions to science until the Middle Ages. De Materia Medica was widely read for more than 1,500 years, important contributions from the medieval Muslim world include Ibn Wahshiyyas Nabatean Agriculture, Abū Ḥanīfa Dīnawarīs the Book of Plants, and Ibn Bassals The Classification of Soils.
In the early 13th century, Abu al-Abbas al-Nabati, and Ibn al-Baitar wrote on botany in a systematic and scientific manner and these gardens continued the practical value of earlier physic gardens, often associated with monasteries, in which plants were cultivated for medical use. They supported the growth of botany as an academic subject, lectures were given about the plants grown in the gardens and their medical uses demonstrated. Botanical gardens came much to northern Europe, the first in England was the University of Oxford Botanic Garden in 1621, throughout this period, botany remained firmly subordinate to medicine. German physician Leonhart Fuchs was one of the three German fathers of botany, along with theologian Otto Brunfels and physician Hieronymus Bock and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification, physician Valerius Cordus authored a botanically and pharmacologically important herbal Historia Plantarum in 1544 and a pharmacopoeia of lasting importance, the Dispensatorium in 1546.
Naturalist Conrad von Gesner and herbalist John Gerard published herbals covering the medicinal uses of plants, naturalist Ulisse Aldrovandi was considered the father of natural history, which included the study of plants
The epidermis is a single layer of cells that covers the leaves, flowers and stems of plants. It forms a boundary between the plant and the external environment, the epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds, and absorbs water and mineral nutrients. The epidermis of most leaves shows dorsoventral anatomy, the upper and lower surfaces have somewhat different construction, woody stems and some other stem structures produce a secondary covering called the periderm that replaces the epidermis as the protective covering. The epidermis is the outermost cell layer of the plant body. Most plants have an epidermis that is a cell layer thick. Some plants like Ficus elastica and Peperomia, which have periclinal cellular division within the protoderm of the leaves, have an epidermis with multiple cell layers, epidermal cells are tightly linked to each other and provide mechanical strength and protection to the plant. The walls of the cells of the above ground parts of plants contain cutin.
The cuticle reduces water loss to the atmosphere, it is covered with wax in smooth sheets. The wax layers give some plants a whitish or bluish surface color, surface wax acts as a moisture barrier and protects the plant from intense sunlight and wind. The underside of leaves have a thinner cuticle than the top side. The epidermal tissue includes several differentiated cell types, epidermal cells, guard cells, subsidiary cells, the epidermal cells are the most numerous and least specialized. These are typically more elongated in the leaves of monocots than in those of dicots, trichomes or hairs grow out from the epidermis in many species. In root epidermis, epidermal hairs, termed root hairs are common and are specialized for absorption of water, in plants with secondary growth, the epidermis of roots and stems is usually replaced by a periderm through the action of a cork cambium. The stomatal complex regulates the exchange of gases and water vapor between the air and the interior of the leaf.
Typically, the stomata are more numerous over the abaxial epidermis of the leaf than the upper epidermis, an exception is floating leaves where most or all stomata are on the upper surface. Vertical leaves, such as those of grasses, often have roughly equal numbers of stomata on both surfaces. The stoma is bounded by two guard cells, according to one theory, in sunlight the concentration of potassium ions increases in the guard cells. This, together with the sugars formed, lowers the potential in the guard cells
International Standard Book Number
The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay.
The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces.
Separating the parts of a 10-digit ISBN is done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
Xylem is one of the two types of transport tissue in vascular plants, phloem being the other. The basic function of xylem is to water from roots to shoots and leaves. The word xylem is derived from the Greek word ξύλον, meaning wood, the most distinctive xylem cells are the long tracheary elements that transport water. Tracheids and vessel elements are distinguished by their shape, vessel elements are shorter, Xylem contains two other cell types and fibers. In transitional stages of plants with secondary growth, the first two categories are not mutually exclusive, although usually a vascular bundle will contain primary xylem only, the branching pattern exhibited by xylem follows Murrays law. Primary xylem is formed during growth from procambium. Metaxylem develops after the protoxylem but before secondary xylem, metaxylem has wider vessels and tracheids than protoxylem. Secondary xylem is formed during growth from vascular cambium. All species have secondary xylem, which is uniform in structure throughout this group.
Many conifers become tall trees, the xylem of such trees is used and marketed as softwood. Angiosperms, there are some quarter of a million to four hundred species of angiosperms. Within this group secondary xylem is rare in the monocots, many non-monocot angiosperms become trees, and the secondary xylem of these is used and marketed as hardwood. The xylem transports water and soluble mineral nutrients from the throughout the plant. It is used to replace water lost during transpiration and photosynthesis, Xylem sap consists mainly of water and inorganic ions, although it can contain a number of organic chemicals as well. The transport is passive, not powered by energy spent by the elements themselves. Transporting sap upwards becomes more difficult as the height of a plant increases, the phloem pressure can rise to several MPa, far higher than atmospheric pressure. Selective inter-connection between these systems allows this high concentration in the phloem to draw xylem fluid upwards by negative pressure.
Transpirational pull, the evaporation of water from the surfaces of cells to the atmosphere creates a negative pressure at the top of a plant
The ground tissue of plants includes all tissues that are neither dermal nor vascular. It can be divided into three based on the nature of the cell walls. Parenchyma cells have thin walls and usually remain alive after they become mature. Parenchyma forms the tissue in the soft parts of plants. Collenchyma cells have thin walls with some areas of secondary thickening. Collenchyma provides extra support, particularly in regions of new growth. Sclerenchyma cells have thick lignified secondary walls and often die when mature, sclerenchyma provides the main structural support to a plant. Parenchyma is a versatile ground tissue that generally constitutes the filler tissue in parts of plants. It forms, among other things, the cortex and pith of stems, the cortex of roots, the mesophyll of leaves, the pulp of fruits, parenchyma cells are living cells and may remain meristematic at maturity—meaning that they are capable of cell division if stimulated. They have thin but flexible cellulose cell walls, and are generally polyhedral when close-packed and they have large central vacuoles, which allow the cells to store and regulate ions, waste products, and water.
Tissue specialised for food storage is commonly formed of parenchyma cells, chlorenchyma cells carry out photosynthesis and manufacture food. The shape of parenchyma cells varies with their function and these cells, along with the epidermal guard cells of the stoma, form a system of air spaces and chambers that regulate the exchange of gases. Shapes of parenchyma 1= polyhedral 2=stellate 3=elongated 4=lobed The first use of collenchyma was by Link who used it to describe the sticky substance on Bletia pollen, collenchyma tissue is composed of elongated cells with irregularly thickened walls. They provide structural support, particularly in growing shoots and leaves, collenchyma tissue makes up things such as the resilient strands in stalks of celery. Collenchyma cells are living, and have only a thick primary cell wall made up of cellulose. Cell wall thickness is strongly affected by mechanical stress upon the plant, the walls of collenchyma in shaken plants, may be 40–100% thicker than those not shaken.
Sclerenchyma is the tissue in plants. Two types of sclerenchyma cells exist and sclereids and their cell walls consist of cellulose and lignin
A stem is one of two main structural axes of a vascular plant, the other being the root. The stem is divided into nodes and internodes, The nodes hold one or more leaves. Adventitious roots may be produced from the nodes, the internodes distance one node from another. The term shoots is often confused with stems, shoots generally refers to new plant growth including both stems and other structures like leaves or flowers. In most plants stems are located above the surface but some plants have underground stems. Stems have four main functions which are, Support for and the elevation of leaves, the stems keep the leaves in the light and provide a place for the plant to keep its flowers and fruits. Transport of fluids between the roots and the shoots in the xylem and phloem Storage of nutrients Production of new living tissue, the normal lifespan of plant cells is one to three years. Stems have cells called meristems that annually generate new living tissue, Stems are often specialized for storage, asexual reproduction, protection or photosynthesis, including the following, Acaulescent – used to describe stems in plants that appear to be stemless.
Actually these stems are just extremely short, the leaves appearing to rise out of the ground. Arborescent – tree like with woody stems normally with a single trunk, branched – aerial stems are described as being branched or unbranched Bud – an embryonic shoot with immature stem tip. Bulb – a short underground stem with fleshy storage leaves attached, e. g. onion, daffodil. Bulbs often function in reproduction by splitting to form new bulbs or producing small new bulbs termed bulblets, bulbs are a combination of stem and leaves so may better be considered as leaves because the leaves make up the greater part. Caespitose – when stems grow in a mass or clump or in low growing mats. Cladode – a flattened stem that appears more-or-less leaf like and is specialized for photosynthesis, climbing – stems that cling or wrap around other plants or structures. Corm – a short enlarged underground, storage stem, e. g. taro, decumbent – stems that lie flat on the ground and turn upwards at the ends. Fruticose – stems that grow shrublike with woody like habit, herbaceous – non woody, they die at the end of the growing season.
Pedicel – stems that serve as the stalk of a flower in an inflorescence or infrutescence. Peduncle – a stem that supports an inflorescence Prickle – a sharpened extension of the outer layers
In vascular plants, phloem is the living tissue that transports the soluble organic compounds made during photosynthesis, in particular the sugar sucrose, to all parts of the plant where needed. This transport process is called translocation, in trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word φλοιός meaning bark. Sieve elements are the type of cell that are responsible for transporting sugars throughout the plant, at maturity they lack a nucleus and have very few organelles, so they rely on companion cells or albuminous cells for most of their metabolic needs. All sieve cells have groups of pores at their ends that grow from modified and enlarged plasmodesmata, the pores are reinforced by platelets of a polysaccharide called callose. They are of three types, The metabolic functioning of sieve-tube members depends on an association with the companion cells. The dense cytoplasm of a cell is connected to the sieve-tube element by plasmodesmata.
The common sidewell shared by a sieve tube element and a cell has large numbers of plasmodesmata. There are two types of companion cells, ordinary companion cells, which have smooth walls and few or no plasmodesmatal connections to cells other than the sieve tube. Transfer cells, which have much-folded walls that are adjacent to non-sieve cells and they are specialized in scavenging solutes from those in the cell walls that are actively pumped requiring energy. Albuminous cells have a role to companion cells, but are associated with sieve cells only and are hence found only in seedless vascular plants. Other parenchyma cells within the phloem are generally undifferentiated and used for food storage, although its primary function is transport of sugars, phloem may contain cells that have a mechanical support function. These generally fall into two categories and sclereids, both cell types have a secondary cell wall and are therefore dead at maturity. The secondary cell wall increases their rigidity and tensile strength, bast fibres are the long, narrow supportive cells that provide tension strength without limiting flexibility.
They are found in xylem, and are the component of many textiles such as paper, linen. Sclereids are irregularly shaped cells that add compression strength but may reduce flexibility to some extent and they serve as anti-herbivory structures, as their irregular shape and hardness will increase wear on teeth as the herbivores chew. For example, they are responsible for the gritty texture in pears, unlike xylem, the phloem is composed of still-living cells that transport sap. The sap is a solution, but rich in sugars made by photosynthesis. These sugars are transported to parts of the plant, such as the roots, or into storage structures
Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store, in eudicots, pith is located in the center of the stem. In monocots, it into flowering stems and roots. The pith is encircled by a ring of xylem, the xylem, while new pith growth is usually white or pale in color, as the tissue ages it commonly darkens to a deeper brown color. In trees pith is generally present in young growth, but in the trunk, in some plants, the pith in the middle of the stem may dry out and disintegrate, resulting in a hollow stem. A few plants, such as walnuts, have distinctive chambered pith with numerous short cavities, the cells in the peripheral parts of the pith may, in some plants, develop to be different from cells in the rest of the pith. This layer of cells is called the perimedullary region of the pithamus. An example of this can be observed in Hedera helix, a species of ivy, the term pith is used to refer to the pale, spongy inner layer of the rind - more properly called mesocarp or albedo - of citrus fruits and other hesperidia.
The word comes from the Old English word piþa, meaning substance, akin to Middle Dutch pitt, the pith of the sola or other similar plants is used to make the pith helmet. The pith of the palm, although highly toxic to animals in its raw form, is an important human food source in Melanesia and Micronesia by virtue of its starch content. There is an easy, primitive process of extraction from sago pith that leaches away a sufficient amount of the toxins. The form of the starch after processing is similar to tapioca
Bast fibre is plant fibre collected from the phloem or bast surrounding the stem of certain dicotyledonous plants. They support the conductive cells of the phloem and provide strength to the stem, Bast fibres are classified as soft fibres, and are flexible. Fibres from monocotyledonous plants, called leaf fibre, are classified as hard fibres and are stiff, since the valuable fibres are located in the phloem, they must often be separated from the xylem material, and sometimes from the epidermis. The process for this is called retting, and can be performed by micro-organisms either on land or in water, in the phloem, bast fibres occur in bundles that are glued together by pectin and calcium ions. More intense retting separates the fibre bundles into elementary fibres, that can be several centimetres long, often bast fibres have higher tensile strength than other kinds, and are used in high-quality textiles, yarn, composite materials and burlap. An important property of bast fibres is that they contain a structure, the fibre node, that represents a weak point.
Seed hairs, such as cotton, do not have nodes, from prehistoric times through at least the early 20th century, bast shoes were woven from bast strips in the forest areas of Eastern Europe. Where no other source of tanbark was available, bast has used for tanning leather. International Jute Study Group Bast Fibre cords in Viking ships Bast fibre production with hemp