* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download CB098-008.44 - Workforce Solutions
Survey
Document related concepts
History of botany wikipedia , lookup
Plant secondary metabolism wikipedia , lookup
Plant breeding wikipedia , lookup
Evolutionary history of plants wikipedia , lookup
Plant physiology wikipedia , lookup
Plant ecology wikipedia , lookup
Ecology of Banksia wikipedia , lookup
Ornamental bulbous plant wikipedia , lookup
Plant morphology wikipedia , lookup
Plant evolutionary developmental biology wikipedia , lookup
Perovskia atriplicifolia wikipedia , lookup
Pollination wikipedia , lookup
Plant reproduction wikipedia , lookup
Transcript
The Flower & Sexual Reproduction The Flower: Site of Sexual Reproduction The flower is the site where sexual reproduction occurs in angiosperms and it leads to the formation of seeds. Complete Sexual Cycle 1) The Production of reproductive cells after meiosis. 2) Pollination. 3) Fertilization Artichoke 4) Seed & Fruit Development. 5) Seed & Fruit Dissemination. 6) Seed Germination. Note: Angiosperms are the flowering plants. They belong to the division Magnoliophyta (Anthophtya). Remember that divisions are right below kingdoms in the taxonomic hierarchy. Complete Flower Parts & Their Function Flowers are made of 4 whorls of modified leaves. These whorls are stamens, carpels, sepals and petals. Complete “Flower Assignment” before continuing to the next slide. Pollination The Male Flower Organs Are The Androecium. The Generative Cell divides to form sperm cells. mitosis After landing on a stigma (female part), the dry pollen grain absorbs water from the stigma, becomes hydrated and then germinates and grows a pollen tube. Then sperm cells go down the tube. The Pollen Grain is the male gametophyte (Note: The gametophyte is the gamete producing plant). It is a 2-celled, haploid structure that produces sperm cells for fertilization. The Female Flower Organs Are The Gynoecium. Simple & Compound Pistils Compared. Pea has a simple pistil, showing an ovary composed of a single carpel. Tulip has a compound pistil showing an ovary with 3 fused carpels. Pea The Gynoecium can be a single carpel (simple pistil) where the ovary resides. The ovary can be many carpels. Compound Pistil – A group of fused carpels. The Pea has a single carpel (simple pistil) with multi ovules present. Tulip Ovary – A hollow structure, having several chambers (locules). Locule – Chamber; a cavity of the ovary in which ovules occur. Ovule – A rudimentary seed before fertilization. Stigmas Locules Carpels Pea 1 1 1 Tulip 3 3 3 The tissue within the ovary to which an ovule is attached is called the Placenta. This figure indicates 3 types of placentation: a) parietal, b) axile, & c) central. The Embryo Sac is the Female Gametophyte Plant. Embryo Sac – The female gametophyte of angiosperms contained in the ovule of a flowering plant. Generally, a 7-celled structure with all cells being haploid or n . 7 CELLS 3 Antipodal nuclei (Each haploid). These will form 3 antipodal cells. 1 Endosperm mother cell with 2 haploid nuclei. This is the central cell. 1 Egg Cell 2 Synergids (Haploid or n) Embryo Sac Development in Cotton 3 Megaspores Disintegrate (Haploid or n) Double Fertilization Produces an Embryo & the Endosperm Within the embryo sac (female), the synergids emit signals, so the pollen tube (male) will travel to the micropyle of the ovule. In the pollen tube, 2 sperm cells are traveling. 1) After reaching the embryo sac, one sperm fuses with the egg. Sperm (n) + egg (n) will form a diploid zygote (2n). Later, the zygote will form the embryo. 2) The other sperm fuses with the central cell. Sperm (n) + polar nuclei (polar bodies (2n) of the central cell will form a triploid (3n) primary endosperm nucleus. Later, the primary endosperm nucleus will become the endosperm (the nutritive tissue formed within the embryo sac of seed plants; it often is consumed as the seed matures, but remains in the seeds of many monocots). The double fusion of egg with sperm and polar nuclei with sperm is called Double Fertilization. Now the conditions are set for development of the seed and fruit. After fertilization, the ovule becomes the seed and the ripened ovary becomes the fruit. In monocots, food reserves remain in the endosperm. In dicots, the food reserves of the endosperm are transported to the cotyledons and consequently, the mature dicot seed lacks endosperm. Apical Meristems: Sites of Flower Development As we discussed in previous chapters, the shoot apex or SAM produces stems and leaves. At some time during the growing season, a signal (for example, day length or temperature) will trigger a change in the metabolism of certain shoot apices, thereby starting its transformation into a floral apex. This apex now becomes the floral apical meristem (FAM). At the FAM, Bracts are the first to develop. Bract – a modified leaf, from the axil of which gives rise to a flower or an inflorescence. Inflorescence – a flower cluster. Floral organs are modified leaves. Therefore, the flower itself is really a shortened and modified branch. Flowers Vary In Their Architecture A Complete Flower has all four sets of floral leaves or parts (Sepals, Petals, Stamens and Carpels). An Incomplete Flower lacks at least 1 of the floral leaves or parts. Perfect Flowers have both male and female parts present in one flower. These are bisexual flowers. Therefore, a perfect flower is a complete flower if it also has sepals and petals. An Imperfect Flower is missing one gender. These are unisexual flowers. They have either male or female parts. The types of imperfect flowers are: Staminate Flowers – possess male parts. Pistilliate Flowers – possess female parts. Is a pistillate flower, a complete or incomplete flower? Must a complete flower be a perfect flower? Can an incomplete flower be a perfect flower? Staminate and pistillate flowers can occur on the same plant. Examples are Corn, Walnut, Oak. If a plant produces male and female gametes in the same flower on one plant or on different flowers on the same plant, the plant is monoecious. Monoecious – A plant that produces male and female gametes on the same individual. Walnut Dioecious – unisexual, having the male and female elements in different individuals. Staminate and pistillate flowers on separate individual plants. So an individual could be classified as male or female. Example: Asparagus, willow, Kentucky coffee tree, ginkgo. Symmetry of Flowers Regular Symmetry – Divide in different Places and still have 2 equal parts A regular flower has a corolla made up of similarly shaped petals equally spaced and radiating form the enter of the flower; star shaped flower; actinomorphic flower. Irregular Symmetry – Divide only in one place and still have 2 equal parts. An irregular flower has parts so that only one line can divide the flower into 2 equal halves or mirror images; zygomorhic flower. Ovary Position Superior Ovary – The gynoecium is situated on the receptacle above the Tulip with point of origin of the perianth & Superior androecium. Ovary Inferior Ovary – Gynoecium is below the apparent points of attachment of the perianth & androecium. The lower portions of the 3 outer whorls - calyx, corolla and androecium are fused in a Daffodil with tube called a hypanthium. Inferior Ovary Almond (Inferior Ovary), the hypanthium is not fused to the ovary. Often Flowers Occur in Clusters or Inflorescences Inflorescence – a flower cluster or flowering branch. Raceme – Simple, pedicels (short branches) present. Panicle – Branched raceme. Catkin – Spike with only pistillate or staminate flowers (See previous slide on Walnut). Umbel – short floral axis & flowers arise in an umbrella-like fashion from the same level. Spike – Like a raceme but no pedicel. Head – Flowers lack pedicel & are crowed together (Asteraceace Family; this includes the sunflowers or composites). Cyme – One flower on main axis & other lateral flowers present. Reproductive Strategies: Self-Pollination & Cross-Pollination Self Pollination (Selfing) – This is when pollen is transferred from the anther to stigma on the same flower or pollen from one flower to another flower on the same plant. Selfing is sexual reproduction because there is a joining of egg and sperm but the resulting embryo has only one parent. Selfing can be prevented if a plant is dioecious. Why? Selfing can also be prevented if the stigma inhibits pollen tube growth or if on the same plant, the anther releases pollen some time before the stigma on the same plant matures (Receptive to Pollen). Selfing can be beneficial if plants are scattered or if pollinators are rare. Selfing can save energy by putting very low resources into pollen production. In some selfers, the flowers never open. These flowers remain small and budlike, and the pollen falls from the anther sacs onto the stigma while the flower parts are still close together. Some seeds are produced with no fertilization at all. This is parthenogenesis. Cross Pollination (Outcrossing) – This is when pollen is transferred from the anther of one individual plant to the stigma of another individual plant of the same species. Cross pollination occurs between genetically distinct individuals. Cross pollination results in genetic recombination, leading to genetically diverse offspring. This is important for adaptation. Pollination is Affected By Vectors Vectors transfer pollen from anther to stigma. A Pollination Syndrome is when there are unique flower and pollen traits that adapt a flower for pollination by a particular vector. In other words, flowers are adapted to be pollinated by certain vectors. Vectors can be nonliving (abiotic) or biotic (living). Biotic Vectors – Insects (Beetles, Flies, Bees and Relatives, Butterflies, Moths), Birds and Bats. Biotic Vectors carry and transfer pollen and obtain rewards themselves. Such rewards can be nectar, pollen (can be eaten), waxes and oils. Flowers and biotic vectors are adapted (or fit) to each other and are mutualistic (both benefit) in nature. - A Nectary is a nectar-secreting gland that is found in flowers. Nectar occurs in tubes or pools. Nectar may be available only for a precise period of time. Nectar is made mostly sugar. - In order to find the nectar, biotic vectors follow Nectar Guides on the plant. Nectar guides are various markings that direct the pollinator to the flower’s sexual organs and source of nectar. In addition, some flowers emit strong odors while others may rely on colors to attract biotic vectors. - When considering honeybees, they need 18% sugar concentration otherwise the act of finding nectar would be an energy loss. - Some bee species take up oil from flowers (2,000 plant species produce oil instead of nectar) instead of nectar. The energy content of oil – twice that of sugar – makes it a suitable food for bee larvae. Some flowers are built with no landing platform for pollinators. Biotic vectors, such as hummingbirds must hover. - Certain flowers open at night for bat pollination. In addition, some female orchids mimic female bees, which attract male bees. Abiotic Vectors – Wind or Water. Pollen is carried by nonliving items. Examples of plants pollinated by abiotic vectors: Grasses, Many Trees. Plants with abiotic vectors usually have no nectar. Flowers on these plants are often small, colorless and odorless. Petals are often lacking and reduced to small scales. These plants release much more pollen than (biotic vector) flowers. One single rye or corn plant can release 20 million pollen grains and one dock plant can release 400 million pollen grains. Plants must saturate the surroundings and hope pollen lands on the stigma of other plants. Stigmatic surfaces are enlarged and elaborate, often extending outside the flower to receive the pollen. Note: Wind and insect pollination are not mutually exclusive (See Figure 13.20) in your text. Wind-pollinated Flower. The architecture of jojoba flowers (Simondsia chinensis) creates vortices of air currents that bring pollen grains to the stigmatic surfaces. BIO 141 Botany with Laboratory • This product is sponsored by a grant awarded under the President’s Community-Based Job Training Grants as implemented by the U.S. Department of Labor’s Employment and Training Administration. The information contained in this product was created by a grantee organization and does not necessarily reflect the official position of the U.S. Department of Labor. All references to non-governmental companies or organizations, their services, products, or resources are offered for informational purposes and should not be construed as an endorsement by the Department of Labor. This product is copyrighted by the institution that created it and is intended for individual organizational, non-commercial use only.