Gynoecium is most used as a collective term for the parts of a flower that produce ovules and develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; the gynoecium is referred to as the "female" portion of the flower, although rather than directly producing female gametes, the gynoecium produces megaspores, each of which develops into a female gametophyte which produces egg cells. The term gynoecium is used by botanists to refer to a cluster of archegonia and any associated modified leaves or stems present on a gametophyte shoot in mosses and hornworts; the corresponding terms for the male parts of those plants are clusters of antheridia within the androecium. Flowers that bear a gynoecium but no stamens are called carpellate. Flowers lacking a gynoecium are called staminate; the gynoecium is referred to as female because it gives rise to female gametophytes. Gynoecium development and arrangement is important in systematic research and identification of angiosperms, but can be the most challenging of the floral parts to interpret.
The gynoecium may consist of one or more separate pistils. A pistil consists of an expanded basal portion called the ovary, an elongated section called a style and an apical structure that receives pollen called a stigma; the ovary, is the enlarged basal portion which contains placentas, ridges of tissue bearing one or more ovules. The placentas and/or ovule may be born on the gynoecial appendages or less on the floral apex; the chamber in which the ovules develop is called a locule. The style, is a pillar-like stalk; some flowers such as Tulipa do not have a distinct style, the stigma sits directly on the ovary. The style is a hollow tube in some plants such as lilies, or has transmitting tissue through which the pollen tubes grow; the stigma, is found at the tip of the style, the portion of the carpel that receives pollen. It is sticky or feathery to capture pollen; the word "pistil" comes from Latin pistillum meaning pestle. A sterile pistil in a male flower is referred to as a pistillode; the pistils of a flower are considered to be composed of carpels.
A carpel is the female reproductive part of the flower, interpreted as modified leaves bearing structures called ovules, inside which the egg cells form. A pistil may consist of one carpel, with its ovary and stigma, or several carpels may be joined together with a single ovary, the whole unit called a pistil; the gynoecium may consist of one multi-carpellate pistil. The number of carpels is described by terms such as tricarpellate. Carpels are thought to be phylogenetically derived from ovule-bearing leaves or leaf homologues, which evolved to form a closed structure containing the ovules; this structure is rolled and fused along the margin. Although many flowers satisfy the above definition of a carpel, there are flowers that do not have carpels according to this definition because in these flowers the ovule, although enclosed, are borne directly on the shoot apex, only become enclosed by the carpel. Different remedies have been suggested for this problem. An easy remedy that applies to most cases is to redefine the carpel as an appendage that encloses ovule and may or may not bear them.
If a gynoecium has a single carpel, it is called monocarpous. If a gynoecium has multiple, distinct carpels, it is apocarpous. If a gynoecium has multiple carpels "fused" into a single structure, it is syncarpous. A syncarpous gynoecium can sometimes appear much like a monocarpous gynoecium; the degree of connation in a syncarpous gynoecium can vary. The carpels retain separate styles and stigmas; the carpels may be "fused" except for retaining separate stigmas. Sometimes carpels possess distinct ovaries. In a syncarpous gynoecium, the "fused" ovaries of the constituent carpels may be referred to collectively as a single compound ovary, it can be a challenge to determine. If the styles and stigmas are distinct, they can be counted to determine the number of carpels. Within the compound ovary, the carpels may have distinct locules divided by walls called septa. If a syncarpous gynoecium has a single style and stigma and a single locule in the ovary, it may be necessary to examine how the ovules are attached.
Each carpel will have a distinct line of placentation where the ovules are attached. Pistils begin as small primordia on a floral apical meristem, forming than, closer to the apex than sepal and stamen primordia. Morphological and molecular studies of pistil ontogeny reveal that carpels are most homologous to leaves. A carpel has a similar function to a megasporophyll, but includes a stigma, is fused, with ovules enclosed in the enlarged lower portion, the ovary. In some basal angiosperm lineages and Winteraceae, a carpel begins as a shallow cup where the ovules de
RoboBee is a tiny robot capable of untethered flight, developed by a research robotics team at Harvard University. The culmination of twelve years of research, RoboBee solved two key technical challenges of micro-robotics. Engineers invented a process inspired by pop-up books that allowed them to build on a sub-millimeter scale and efficiently. To achieve flight, they created artificial muscles capable of beating the wings 120 times per second; the goal of the RoboBee project is to make a autonomous swarm of flying robots for applications such as search and rescue and artificial pollination. To make this feasible, researchers need to figure out how to get power supply and decision making functions, which are supplied to the robot via a tiny tether, integrated with the main body; the 3-centimeter wingspan of RoboBee makes it the smallest man-made device modeled on an insect to achieve flight. For more than a decade, researchers at Harvard University have been working on developing tiny flying robots.
The United States Defense Advanced Research Projects Agency funded early research in the hopes that it would lead to stealth surveillance solutions for the battlefield and urban situations. Inspired by the biology of a fly, early efforts focused on getting the robot airborne. Flight was achieved in 2007, but forward motion required a guideline since it was not possible to build control mechanisms on board. UC Berkeley robotics researcher Ron Fearing called the achievement "a major breakthrough" for micro scale robotics; the concept of micro-scale flying systems was not new. The "DelFly" was capable of untethered self-controlled forwards flight, while Micromechanical Flying Insect research devices had sufficient power for hovering, but lacked self-sustained flight capacity. Based on the promise of the early robotic fly experiments, the RoboBee project was launched in 2009 to investigate what it would take to "create a robotic bee colony". Achieving controlled flight proved exceedingly difficult, requiring the efforts of a diverse group: vision experts, materials scientists, electrical engineers.
During the summer of 2012, the researchers solved key technical challenges allowing their robotic creation, nicknamed RoboBee, to take its first controlled flight. The results of their research were published in Science in early May 2013. According to the RoboBee researchers, previous efforts to miniaturize robots were of little help to them because RoboBee's small size changes the nature of the forces at play. Engineers had to figure out how to build without rotary motors and nuts and bolts, which are not viable on such a small scale. In 2011, they developed a technique where they cut designs from flat sheets, layered them up, folded the creation into shape. Glue was used to hold the folded parts together, analogous to origami; the technique replaced earlier ones that were slower and less precise and used less durable materials. The manufacturing process, inspired by pop-up books, enables the rapid production of prototype RoboBee units. At micro scale, a small amount of turbulence can have a dramatic impact on flight.
To overcome it, researchers had to make RoboBee react rapidly. For the wings, they built "artificial muscles" using a piezoelectric actuator - a thin ceramic strip that contracts when electric current is run across it. Thin plastic hinges serve as joints; the design allows the robots to generate power output comparable with an insect of equal size. Each wing can be controlled separately in real time; the ultimate goal of the project is to make colonies of autonomous and wireless RoboBees. As of 2013, two problems remain unsolved. First, the robot is too small for the smallest encapsulated microchips, meaning there is no way for the robots to make decisions; the RoboBee has onboard vision sensors, but the data requires transmission to a tethered "brain subsystem" for interpretation. Work continues on specialized hardware accelerators in an aim to solve the problem. Second, the researchers have not figured out. "The power question proves to be something of a catch-22", remarked Wood. "A large power unit stores more energy but demands a larger propulsion system to handle the increased weight, which in turn requires an bigger power source."
Instead the robots have to be tethered with tiny cords. A recent progress in on-board power management is the demonstration of reversible, energy-efficient perching on overhangs; this allows the prototype to remain at a high vantage point. If researchers solve the microchip and power issues, it is believed that groups of RoboBees utilizing swarm intelligence will be useful in search and rescue efforts and as artificial pollinators. To achieve the goal of swarm intelligence, the research team has developed two abstract programming languages – Karma which uses flowcharts, OptRAD which uses probabilistic algorithms. Potential applications for individual or small groups of RoboBees include covert surveillance and the detection of harmful chemicals. Parties such as the Electronic Frontier Foundation have raised concerns about the civilian privacy impacts of military and government use of miniature flying robots. In some areas, such as the state of Texas and the city of Charlottesville, regulators have restricted their use by the general public.
According to the project researchers, the "pop-up" manufacturing process would enable automated mass production of RoboBees in the future. Harvard's Wyss Institute is in the process of commercializing the folding and pop-up techniques invented for the project. RoboBee's wingspan is
Pollination management is the label for horticultural practices that accomplish or enhance pollination of a crop, to improve yield or quality, by understanding of the particular crop's pollination needs, by knowledgeable management of pollenizers and pollination conditions. While people think first of the European honey bee when pollination comes up, in fact there are many different means of pollination management that are used, both other insects and other mechanisms. There are other insects commercially available that are more efficient, like the blue orchard bee for fruit and nut trees, local bumblebees better specialized for some other crops, hand pollination, essential for production of hybrid seeds and some greenhouse situations, pollination machines. With the decline of both wild and domestic pollinator populations, pollination management is becoming an important part of horticulture. Factors that cause the loss of pollinators include pesticide misuse, unprofitability of beekeeping for honey, rapid transfer of pests and diseases to new areas of the globe, urban/suburban development, changing crop patterns, clearcut logging, clearing of hedgerows and other wild areas, bad diet because of loss of floral biodiversity, a loss of nectar corridors for migratory pollinators.
The increasing size of fields and orchards increase the importance of pollination management. Monoculture can cause a brief period when pollinators have more food resources than they can use while other periods of the year can bring starvation or pesticide contamination of food sources. Most nectar pollen source throughout the growing season to build up their numbers. Crops that traditionally have had managed pollination include apple, pears, some plum and cherry varieties, cranberries, cantaloupe, alfalfa seeds, onion seeds, many others; some crops that have traditionally depended on chance pollination by wild pollinators need pollination management nowadays to make a profitable crop. Many of these were at one time universally turning to honeybees, but as science has shown that honeybees are inefficient pollinators, demand for other managed pollinators has risen. While honeybees may visit dozens of different kinds of flowers, diluting the orchard pollen they carry, the Blue orchard bee will visit only the intended tree, producing a much higher fertilization rate.
The focus on the specific tree makes the orchard bee 100 times more efficient at pollinating, per bee. Some crops when planted in a monoculture situation, require a high level of pollinators to produce economically viable crops if depending on the more generalized honeybee; this may be because of lack of attractiveness of the blossoms, or from trying to pollinate with an alternative when the native pollinator is extinct or rare. These include crops such as alfalfa and kiwifruit; this technique is known as saturation pollination. In many such cases, various native bees are vastly more efficient at pollination, but the inefficiency of the honey bees is compensated for by using large numbers of hives, the total number of foragers thereby far exceeding the local abundance of native pollinators. In a few cases, it has been possible to develop commercially viable pollination techniques that use the more efficient pollinators, rather than continued reliance on honey bees, as in the management of the alfalfa leafcutter bee.
In the case of the kiwifruit, its flowers do not produce nectar, so that honeybees are reluctant to visit them, unless present in such overwhelming numbers that they do so incidentally. This has led bumblebee pollination companies to begin offering their services for kiwifruit, as they appear to be far more efficient at the job than honeybees more efficient than hand pollination, it is estimated. In the 1950s when the woods were full of wild bee trees, beehives were kept on most South Carolina farms, a farmer who grew ten acres of watermelons would be a large grower and had all the pollination needed, but today's grower may grow 200 acres, and, if lucky, there might be one bee tree left within range. The only option in the current economy is to bring beehives to the field during blossom time. Organisms that are being used as pollinators in managed pollination are honey bees, alfalfa leafcutter bees, orchard mason bees. Other species are expected to be added to this list. Humans can be pollinators, as the gardener who hand pollinates her squash blossoms, or the Middle Eastern farmer, who climbs his date palms to pollinate them.
The Cooperative extension service recommends one honey bee hive per acre for standard watermelon varieties to meet this crop's pollination needs. In the past, when fields were small, pollination was accomplished by a mix of bees kept on farms, carpenter bees, feral honey bees in hollow trees and other insects. Today, with melons planted in large tracts, the grower may no longer have hives on the farm. Before pollination needs were understood, orchardists planted entire blocks of apples of a single variety; because apples are self-sterile, different members of a single variety are genetic clones (equivalent to a sin
Plant reproduction is the production of new offspring in plants, which can be accomplished by sexual or asexual reproduction. Sexual reproduction produces offspring by the fusion of gametes, resulting in offspring genetically different from the parent or parents. Asexual reproduction produces new individuals without the fusion of gametes, genetically identical to the parent plants and each other, except when mutations occur. In seed plants, the offspring can be packaged in a protective seed, used as an agent of dispersal. Reproduction in which male and female gametes do not fuse, as they do in sexual reproduction. Asexual reproduction may occur through budding, fission, spore formation and vegetative propagation. Plants have two main types of asexual reproduction in which new plants are produced that are genetically identical clones of the parent individual. Vegetative reproduction involves a vegetative piece of the original plant and is distinguished from apomixis, a replacement for sexual reproduction, in some cases involves seeds.
Apomixis in many plant species and in some non-plant organisms. For apomixis and similar processes in non-plant organisms, see parthenogenesis. Natural vegetative reproduction is a process found in herbaceous and woody perennial plants, involves structural modifications of the stem or roots and in a few species leaves. Most plant species that employ vegetative reproduction do so as a means to perennialize the plants, allowing them to survive from one season to the next and facilitating their expansion in size. A plant that persists in a location through vegetative reproduction of individuals constitutes a clonal colony; the distance that a plant can move during vegetative reproduction is limited, though some plants can produce ramets from branching rhizomes or stolons that cover a wide area in only a few growing seasons. In a sense, this process is not one of reproduction but one of survival and expansion of biomass of the individual; when an individual organism increases in size via cell multiplication and remains intact, the process is called vegetative growth.
However, in vegetative reproduction, the new plants that result are new individuals in every respect except genetic. A major disadvantage to vegetative reproduction, is the transmission of pathogens from parent to offspring. Seeds generated by apomixis are a means of asexual reproduction, involving the formation and dispersal of seeds that do not originate from the fertilization of the embryos. Hawkweed, some Citrus and Kentucky blue grass all use this form of asexual reproduction. Pseudogamy occurs in some plants that have apomictic seeds, where pollination is needed to initiate embryo growth, though the pollen contributes no genetic material to the developing offspring. Other forms of apomixis occur in plants including the generation of a plantlet in replacement of a seed or the generation of bulbils instead of flowers, where new cloned individuals are produced. Asexual reproduction is a type of reproduction where the offspring comes from one parent only, inheriting the characteristics of the parent.
A rhizome is a modified underground stem serving as an organ of vegetative reproduction. Prostrate aerial stems, called runners or stolons, are important vegetative reproduction organs in some species, such as the strawberry, numerous grasses, some ferns. Adventitious buds form on roots on damaged stems, or on old roots; these leaves. A form of budding called suckering is the reproduction or regeneration of a plant by shoots that arise from an existing root system. Species that characteristically produce suckers include Elm and many members of the Rose family such as Rosa and Rubus. Plants like onion, hyacinth and tulips reproduce by dividing their underground bulbs into more bulbs. Other plants like potatoes and dahlia reproduce by a similar method involving underground tubers. Gladioli and crocuses reproduce in a similar way with corms; the most common form of plant reproduction utilized by people is seeds, but a number of asexual methods are utilized which are enhancements of natural processes, including: cutting, budding, division, sectioning of rhizomes, tubers, stolons, etc. and artificial propagation by laboratory tissue cloning.
Asexual methods are most used to propagate cultivars with individual desirable characteristics that do not come true from seed. Fruit tree propagation is performed by budding or grafting desirable cultivars, onto rootstocks that are clones, propagated by stooling. In horticulture, a "cutting" is a branch, cut off from a mother plant below an internode and rooted with the help of a rooting liquid or powder containing hormones; when a full root has formed and leaves begin to sprout anew, the clone is a self-sufficient plant, genetically identical to the mother plant. Examples include cuttings from the stems of blackberries, African violets, verbenas to produce new plants. A related use of cuttings is grafting, where a stem or bud is joine
Pollination is the transfer of pollen from a male part of a plant to a female part of a plant enabling fertilisation and the production of seeds, most by an animal or by wind. Pollinating agents are animals such as insects and bats. Pollination occurs within a species; when pollination occurs between species it can produce hybrid offspring in nature and in plant breeding work. In angiosperms, after the pollen grain has landed on the stigma, it develops a pollen tube which grows down the style until it reaches an ovary. Sperm cells from the pollen grain move along the pollen tube, enter an ovum cell through the micropyle and fertilise it, resulting in the production of a seed. A successful angiosperm pollen grain containing the male gametes is transported to the stigma, where it germinates and its pollen tube grows down the style to the ovary, its two gametes travel down the tube to where the gametophyte containing the female gametes are held within the carpel. One nucleus fuses with the polar bodies to produce the endosperm tissues, the other with the ovule to produce the embryo Hence the term: "double fertilization".
In gymnosperms, the ovule is not contained in a carpel, but exposed on the surface of a dedicated support organ, such as the scale of a cone, so that the penetration of carpel tissue is unnecessary. Details of the process vary according to the division of gymnosperms in question. Two main modes of fertilization are found in gymnosperms. Cycads and Ginkgo have motile sperm that swim directly to the egg inside the ovule, whereas conifers and gnetophytes have sperm that are unable to swim but are conveyed to the egg along a pollen tube; the study of pollination brings together many disciplines, such as botany, horticulture and ecology. The pollination process as an interaction between flower and pollen vector was first addressed in the 18th century by Christian Konrad Sprengel, it is important in horticulture and agriculture, because fruiting is dependent on fertilization: the result of pollination. The study of pollination by insects is known as anthecology. Pollen germination has three stages; the pollen grain is dehydrated so that its mass is reduced enabling it to be more transported from flower to flower.
Germination only takes place after rehydration, ensuring that premature germination does not take place in the anther. Hydration allows the plasma membrane of the pollen grain to reform into its normal bilayer organization providing an effective osmotic membrane. Activation involves the development of actin filaments throughout the cytoplasm of the cell, which become concentrated at the point from which the pollen tube will emerge. Hydration and activation continue. In conifers, the reproductive structures are borne on cones; the cones are either pollen cones or ovulate cones, but some species are monoecious and others dioecious. A pollen cone contains hundreds of microsporangia carried on reproductive structures called sporophylls. Spore mother cells in the microsporangia divide by meiosis to form haploid microspores that develop further by two mitotic divisions into immature male gametophytes; the four resulting cells consist of a large tube cell that forms the pollen tube, a generative cell that will produce two sperm by mitosis, two prothallial cells that degenerate.
These cells comprise a reduced microgametophyte, contained within the resistant wall of the pollen grain. The pollen grains are dispersed by the wind to the female, ovulate cone, made up of many overlapping scales, each protecting two ovules, each of which consists of a megasporangium wrapped in two layers of tissue, the integument and the cupule, that were derived from modified branches of ancestral gymnosperms; when a pollen grain lands close enough to the tip of an ovule, it is drawn in through the micropyle by means of a drop of liquid known as a pollination drop. The pollen enters a pollen chamber close to the nucellus, there it may wait for a year before it germinates and forms a pollen tube that grows through the wall of the megasporangium where fertilisation takes place. During this time, the megaspore mother cell divides by meiosis to form four haploid cells, three of which degenerate; the surviving one develops as a megaspore and divides to form an immature female gametophyte. Two or three archegonia containing an egg develop inside the gametophyte.
Meanwhile, in the spring of the second year two sperm cells are produced by mitosis of the body cell of the male gametophyte. The pollen tube elongates and pierces and grows through the megasporangium wall and delivers the sperm cells to the female gametophyte inside. Fertilisation takes place when the nucleus of one of the sperm cells enters the egg cell in the megagametophyte’s archegonium. In flowering plants, the anthers of the flower produce microspores by meiosis; these undergo mitosis to form male gametophytes. Meanwhile, the ovules produce megaspores by meiosis, further division of these form the female gametophytes, which are strongly reduced, each consisting only of a few cells, one of, the egg; when a pollen grain adheres to the stigma of a carpel it germinates, developing a pollen tube that grows through the tissues of the style, entering the ovule through the micropyle. When the tube reaches the egg sac, two sperm cells pass through it into the female gametophyte and fertil
International Standard Book Number
The International Standard Book Number is a numeric commercial book identifier, intended to be unique. Publishers purchase ISBNs from an affiliate of the International ISBN Agency. An ISBN is assigned to each 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, 10 digits long if assigned before 2007. The method of assigning an ISBN is nation-based and varies from country to country depending on how large the publishing industry is within a country; the initial ISBN identification format was devised 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 ISO 2108. Published books sometimes appear without an ISBN; the International ISBN agency sometimes assigns such books ISBNs on its own initiative.
Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines and newspapers. The International Standard Music Number covers musical scores; the Standard Book Numbering code is a 9-digit commercial book identifier system created by Gordon Foster, Emeritus Professor of Statistics at Trinity College, for the booksellers and stationers WHSmith and others in 1965. The ISBN identification format was conceived in 1967 in the United Kingdom by David Whitaker and in 1968 in the United States by Emery Koltay; the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO 2108. The United Kingdom continued to use the 9-digit SBN code until 1974. ISO has appointed the International ISBN Agency as the registration authority for ISBN worldwide and the ISBN Standard is developed under the control of ISO Technical Committee 46/Subcommittee 9 TC 46/SC 9; 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 second edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has "SBN 340 01381 8" – 340 indicating the publisher, 01381 their serial number, 8 being the check digit; this can be converted to ISBN 0-340-01381-8. Since 1 January 2007, ISBNs have contained 13 digits, a format, compatible with "Bookland" European Article Number EAN-13s. An ISBN is assigned to each variation of a book. For example, an ebook, a paperback, 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, 10 digits long if assigned before 2007. An International Standard Book Number consists of 4 parts or 5 parts: for a 13-digit ISBN, a prefix element – a GS1 prefix: so far 978 or 979 have been made available by GS1, the registration group element, the registrant element, the publication element, a checksum character or check digit. A 13-digit ISBN can be separated into its parts, 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 separate a given ISBN is complicated, because most of the parts do not use a fixed number of digits. ISBN is most used among others special identifiers to describe references in Wikipedia and can help to find the same sources with different description in various language versions. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency, responsible for that country or territory regardless of the publication language; the ranges of ISBNs assigned to any particular country are based on the publishing profile of the country concerned, so the ranges will vary depending on the number of books and the number and size of publishers that are active. Some ISBN registration agencies are based in national libraries or within ministries of culture and thus may receive direct funding from government to support their services. In other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded.
A full directory of ISBN agencies is available on the International ISBN Agency website. Partial listing: Australia: the commercial library services agency Thorpe-Bowker.