What kind of pollination is it when a plant uses its own male and female cells to produce embryos
Flowering plant REPRODUCTION: Fertilization and Fruits
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Flowers | Double Fertilization | Seeds | Fruit | Vegetative propagation | Links
Pollen
Pollen grains (from the greek palynos for dust or pollen) incorporate the male gametophyte ( microgametophyte ) stage of the plant. Pollen grains are produced by meiosis of microspore mother cells that are located forth the inner edge of the anther sacs (microsporangia). The outer function of the pollen is the exine , which is composed of a circuitous polysaccharide, sporopollenin. Inside the pollen are two (or, at most, three) cells that comprise the male gametophyte. The tube cell (also referred to every bit the tube nucleus) develops into the pollen tube . The germ jail cell divides by mitosis to produce two sperm cells. Sectionalisation of the germ cell tin occur before or after pollination.
The tetrad of 4 haploid cells is located inside an anther sac (microsporangium) of Lilium. The higher up image is cropped from gopher://wiscinfo.wisc.edu:2070/I9/.epitome/.bot/.130/Flowering plant/Lilium/Adroecium/Anther_pollen_tetrads.
Mature 2-cell phase of a pollen grain. Note the thick sculptured exine around the pollen grain of Lilium. The higher up image is cropped and reduced from gopher://wiscinfo.wisc.edu:2070/I9/.image/.bot/.130/Angiosperm/Lilium/Adroecium/Mature_2-celled_pollen_grains.
Allergenic Pollen ( poplar , alder , timothy grass , ragweed , sagebrush , scotchbroom ) (SEM x1,000). This prototype is copyright Dennis Kunkel at www.DennisKunkel.com, used with permission.
Pollination
The transfer of pollen from the anther to the female stigma is termed pollination. This is accomplished by a multifariousness of methods. Entomophyly is the transfer of pollen past an insect. Anemophyly is the transfer of pollen by wind. Other pollinators include birds, bats, water, and humans. Some flowers (for case garden peas) develop in such a way as to pollinate themselves. Others have mechanisms to ensure pollination with some other flower.
Flower color is thought to indicate the nature of pollinator: blood-red petals are thought to attract birds, yellow for bees, and white for moths. Wind pollinated flowers take reduced petals, such as oaks and grasses.
Gynoecium
The gynoecium consists of the stigma , fashion , and ovary containing one or more ovules . These iii structures are often termed a pistil or carpel. In many plants, the pistils will fuse for all or role of their length.
Lilium gynoecium. The above image is reduced and relabeled from gopher://wiscinfo.wisc.edu:2070/I9/.prototype/.bot/.130/Flowering plant/Lilium/Flower_dissection/Ovary.
The Stigma and Fashion
The stigma functions as a receptive surface on which pollen lands and germinates its pollen tube. Corn silk is part stigma, part manner. The style serves to move the stigma some distance from the ovary. This distance is species specific.
The Ovary
The ovary contains i or more than ovules, which in turn contain one female gametophyte, also referred to in angiosperms as the embryo sac . Some plants, such as cherry, accept just a single ovary which produces two ovules. Only i ovule volition develop into a seed.
Cantankerous section of an ovary of Lilium. Note the ovules in the center of the ovary. The in a higher place image is reduced from gopher://wiscinfo.wisc.edu:2070/I9/.paradigm/.bot/.130/Flowering plant/Lilium/Gynoecium/L._ovary_x.s. Follow the link to view a larger image.
The Gametophytes
The male gametophyte develops within the pollen grain. The female gametophyte develops inside the ovule. In flowering plants, gametophyte phases are reduced to a few cells dependant for their nutrition on the sporophyte phase. This is the opposite of the pattern seen in the nonvascular plant groups liverworts, mosses, and hornworts (the Bryophyta).
Flowering plant male gametophytes have two haploid nuclei (the germ nucleus and tube nucleus) contained inside the exine of the pollen grain (or microspore ).
Female gametophytes of flowering plants develop inside the ovule ( megaspore ) contained within an ovary at the base of operations of the pistil of the flower. In that location are usually viii (haploid) cells in the female gametophyte: a) one egg, two synergids flanking the egg (located at the micropyle end of the embryo sac); b) two polar nuclei in the center of the embryo sac; and iii converse cells (at the opposite finish of the embryo sac from the egg).
Megaspore mother cell of Lilium. The above image is cropped, reduced, and labeled from gopher://wiscinfo.wisc.edu:2070/I9/.epitome/.bot/.130/Angiosperm/Lilium/Gynoecium/Ovules_megaspore_mother_cell. Follow the link to view a larger epitome.
Four celled stage of the female gametophyte of Lilium. The above prototype is reduced and cropped from gopher://wiscinfo.wisc.edu:2070/I9/.image/.bot/.130/Angiosperm/Lilium/Gynoecium/Embryo_Sac/4-nucleate_stage. Follow that link to view a larger image.
Lilium 8-celled female gametophyte. The above paradigm is cropped and reduced from gopher://wiscinfo.wisc.edu:2070/I9/.epitome/.bot/.130/Flowering plant/Lilium/Gynoecium/Embryo_Sac/8-nucleate_stage. Follow the link to view a larger epitome.
Double Fertilization | Dorsum to Top
The procedure of pollination being accomplished, the pollen tube grows through the stigma and manner toward the ovules in the ovary. The germ jail cell in the pollen grain divides and releases two sperm cells which move downwardly the pollen tube. Once the tip of the tube reaches the micropyle stop of the embryo sac, the tube grows through into the embryo sac through one of the synergids which flank the egg. One sperm jail cell fuses with the egg, producing the zygote which will subsequently develope into the next-generation sporophyte. The 2nd sperm fuses with the two polar bodies located in the centre of the sac, producing the nutritive triploid endosperm tissue that volition provide energy for the embryo's growth and development.
Pollen tube with haploid male gametophyte nuclei. The above image is cropped from http://www.life.umd.edu/pbio100/plso19.jpg.
Germinating Pollen Grain from a Lily, Sauromatum guttatum (SEM x3,300). This image is copyright Dennis Kunkel at www.DennisKunkel.com, used with permission.
Structure of the female person gametophyte (enbryo sac) and the events approaching fertilization. Paradigm from Purves et al., Life: The Science of Biology, fourth Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
The events of "double fertilization" of the egg and polar nuclei by the two sperm cells. Image from Purves et al., Life: The Science of Biological science, quaternary Edition, past Sinauer Assembly (world wide web.sinauer.com) and WH Freeman (world wide web.whfreeman.com), used with permission.
Stages of growth and development of the embryo. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Assembly (www.sinauer.com) and WH Freeman (world wide web.whfreeman.com), used with permission.
Seeds | Back to Summit
Structure of two dicot seeds. Image from Purves et al., Life: The Science of Biology, fourth Edition, by Sinauer Assembly (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
Seeds in a Pod, Arabidopsis sp. (SEM x220). This image is copyright Dennis Kunkel at www.DennisKunkel.com, used with permission.
Fruit | Back to Top
The ovary wall, afterwards fertilization has occurred, develops into a fruit . Fruits may be fleshy, hard, multiple or unmarried. View the Seeds of Life site for illustrations and information about fruits and seeds. Seeds germinate, and the embryo grows into the next gemeration sporophyte.
Kokosnoot fruit containing the seed y'all usually purchase at the grocery shop. Image from Purves et al., Life: The Science of Biology, fourth Edition, past Sinauer Associates (world wide web.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
Vegetative Propagation | Back to Top
Many plants likewise have an asexual method of reproduction. Often some species, such as many orchids, are more frequently propagated vegetatively than via seeds. Tubers are fleshy hugger-mugger stems, as in the Irish white potato. Leaflets are sections of foliage will develop roots and drop off the found, finer cloning the plant. Runners are shoots running along or over the surface of the ground that will sprout a plantlet, which upon settling to the ground develop into a new independant plant.
Links | Back to Pinnacle
- Seeds of Life Some splendid photographs of fruits and seeds also as a ready of links to related topics.
- CSU BioWeb Fruit Key (Steve Wolf at CSU Stanislas) Progress through the cardinal or view the unabridged key. Illustrated too!
- Phytology 3700 (Steve Wolf at CSU Stanislas) Images and notes about flowering plants.
- The Naked Seeds of Pinus Text and prissy graphics on the life bicycle of pines.
- Flowering Plant Family Recognition and World Wide Flowering Plant Family unit Identification (Ray Phillips, Colby Higher) Illustrated guide to the "essential" families for Phillips' class.
- Fruits (Gopher menu from Wisconsin) A collection of images.
- Flower Whorls and Femaleness Text and very nice illustrations of megasporogenesis.
- Institute Biology (Academy of Maryland) Text, outlines, and images that are function of a full general botany grade.
- The angiosperm life cycle (Academy of Manitoba) Text with glossary and a few images.
Text ©1992, 1994, 1997, 1998, 1999, 2000, 2001, by M.J. Farabee, all rights reserved.Employ for educational purposes is encouraged.
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