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Lec8 plant flowers


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Lec8 plant flowers

  1. 1. FLOWER
  2. 2. Flowers Function  Contain the sexual organs for the plant.  Produces fruit, which protects, nourishes and carries seeds.  Attracts insects for pollination.
  3. 3. Basic Flower Structure stigma carpel gynoecium locule style Flower is perfect pollen Flower is monoecious ovule ovary anther filament stamen androecium petal corollareceptacle sepal perianth calyx Perianth is complete pedicel
  4. 4. Parts of the Flower Sepals  Outer covering of the flower bud.  Protects the stamens and pistils when flower is in bud stage.  Collectively known as the calyx.
  5. 5. Parts of the Flower Petals  Brightly colored  Protects stamen & pistils.  Attracts pollinating insects.  Collectively called the corolla.
  6. 6. PetalPetals are used to attract insects into the flower, they mayhave guidelines on them and be scented.StigmaIs covered in a sticky substance that the pollen grains willadhere to.StyleThe style raises the stigma away from the Ovary todecrease the likelihood of pollen contamination. It variesin length.
  7. 7. OvaryThis protects the ovule and once fertilization has takenplace it will become the fruit.OvuleThe Ovule is like the egg in animals and oncefertilization has taken place will become the seed.ReceptacleThis is the flowers attachment to the stalk and insome cases becomes part of the fruit after fertilizatione.g. strawberry.
  8. 8. Flower stalkGives support to the flower and elevates the flower for theinsects.NectaryThis is where a sugary solution called nectar is held toattract insects.SepalSepals protect the flower whilst the flower is developingfrom a bud.
  9. 9. FilamentThis is the stalk of the Anther.Anther•The Anthers contain pollen sacs.•The sacs release pollen on to the outside of theanthers that brush against insects on entering theflowers.•Once the pollen is deposited on the istransferred to the stigma of another flower.•The ovule is then able to be fertilized.
  10. 10. Male Parts Female PartsStamen Pistil OvaryAnther Stigma OvuleFilament StylePollen
  11. 11. Parts of the Flower (Stamen) Male reproductive part  Anther  Produces pollen  Filament  Supports the anther
  12. 12. Parts of the Flower (Pistil) Female reproductive part  Ovary  Enlarged portion at base of pistil  Produces ovules which develop into seeds  Stigma  Holds the pollen grains
  13. 13. Parts of the Flower (Pistil) Style  Connects the stigma with the ovary  Supports the stigma so that it can be pollinated
  14. 14. Parts of the Flower
  15. 15. 2 Types of flowers: Perfect vs. Imperfect Imperfect- a flower that has either all male parts or all female parts EX: cucumbers, pumpkin, and melons Perfect- a flower that has both male and female parts in the same flower EX: roses, lilies, and dandelions
  16. 16. Imperfect Flower Male or female reproductive organs not, but not both. Example:  A male flower has sepals, petals, and stamen, but no pistils.  A female flower has sepals, petals, and pistils, but no stamen.
  17. 17. Perfect Flowers Contains both male and female reproductive structures.
  18. 18. Incomplete Flowers Missing one of the four major parts of the flower.  Stamen  Pistil  Sepal  Petal
  19. 19. Complete Flowers Contains male and female reproductive organs along with petals and sepals.
  20. 20. Some Example Stories:Perfect Flowers:Pea exclusively self-pollinatingHibiscus self-pollinating if not crossedCherry self-incompatible only outcrossesImperfect Flowers:Begonia unisexual but monoeciousHolly unisexual and dioeciousVariable: Cucumber male, perfect, female, parthenocarpic
  21. 21. Flowers Imperfect flowers are always incomplete but…….. Perfect flowers are not always complete and…….. Complete flowers are always perfect.
  22. 22. Importance of Flowers Important in florist & nursery businesses. Many plants are grown solely for their flowers. Plants have flowers to attract insects for pollination, but people grow them for beauty & economic value.
  23. 23. Important Flower Crops
  24. 24. Basic Flower Structure stigma carpel Pistil is simple gynoecium locule style Flower is perfect pollen Flower is monoecious ovule ovary anther superior filament stamen Flower is hypogynous androecium petal corolla sepal perianth receptacle calyx Perianth is complete pedicel
  25. 25. Ovary Superior Flower HypogynousOvary Half-Superior Flower Perigynous Ovary Half-Inferior Flower Epigynous Ovary Inferior
  26. 26. Basic Flower Structure stigma carpel Pistil is simple gynoecium locule style Flower is perfect pollen Flower is monoecious ovule ovary anther superior filament stamen Flower is hypogynous androecium petal corolla sepal perianth receptacle calyx Perianth is complete pedicel
  27. 27. NUMBER OF FLOWER PARTS Dicotyledonous: the flower parts are in multiples of four or five; rarely are they in 3’s Monocotyledonous: the flower parts are in 3’sNATURE OF FLOWERS Regular: when members of each set of organs – the sepals, petals, stamens and pistils are of the same size and shape Irregular: when some members of one or more sets of organs are different in size or shape or both
  28. 28.  Irregular Flowers Papilionaceous: the standard petal or banner, which is usually the largest and mostly showy of the petals is the outermost; the wings or alae are two lateral petals, the keels or carinae, which are usually the two smallest petals, are innermost. Caesalpinaceous: the standard petal, which is usually the smallest, is innermost; the four other petals, which are almost of the same size and shape, are called accessory petals.
  29. 29. Irregular Flowers Bilabiate or two-lipped: the petals are partially united; the corolla lobes (the free ends of partially united petals) from distinct upper and lower lips. Orchidaceous: the flower has three petals, one of which is entirely different in size and shape and is called lip or labellum.
  30. 30. SYMMETRY OF FLOWERS1.Radial/actinomorphic: one that can be divided into two equal halves along any plane passing through the central axis.2. Bilateral/zygomorphic: one that can be divided only into two equal parts by a median vertical cut.
  31. 31. Ovary Superior Flower Hypogynous 1Ovary Half-Superior Flower Perigynous 1 Ovary Half-Inferior Flower Epigynous Ovary Inferior 1
  32. 32. TYPES OF INFLORESCENCETypes DescriptionSpike Axis elongate; floret sessile, becoming progressively younger towards the apexCatkin Inflorescence a spike, and partly covered by a spatheRaceme Axis elongate; florets pedicellate, florets progressively becoming younger towards the apexPanicle A branched racemeCyme Axis elongate ; florets in 3s, the central floret maturing ahead of the other two
  33. 33. TYPES OF INFLORESCENCETypes DescriptionCorymb Inflorescence flat-topped, the florets growing to the same heightUmbel Axis greatly shortened; pedicels of the same length appearing to radiate from a reduced axisHead Sessile florets gathered on a flat receptacle; some plants with florets differentiated into the ray and disc florets
  35. 35. INTERNAL STRUCTURE Ovary wall Funiculus Locule
  36. 36. • Ovule-Embryonic seed consisting of integument(s) or the protective cell layer surrounding the ovule and nucellus or (megasporangium) which undergoes sporogenesis via meiosis• Emrbyo sac-Female gametophyte• Ovary wall- The ovary wall is the wall of the ovary of a flower which eventually develops variously modified in the fruit wall or pericarp• Funiculus-Stalk by which ovule is attached to placenta• Locule- Ovary cavity • Ovary-Ovule-bearing part of pistil
  37. 37.  plant structure that develops into a seed when fertilized. In gymnosperms (conifers and allies) the ovules lie uncovered on the scales of the cone. In angiosperms (flowering plants), one or more ovules are enclosed by the ovary (portion of the carpel, or female reproductive organ). Each ovule is attached by its base to the stalk (funiculus) that bears it. A mature angiosperm ovule consists of a food tissue covered by one or two future seed coats.
  38. 38.  A small opening (the micropyle) in the integuments at the apex of the ovule permits the pollen tube to enter and discharge its sperm nuclei into the embryo sac, a large oval cell in which fertilization and development occur. Variations in form and position of the ovule are significant in plant classification: orthotropous ovules stand out straight into the cavity of the ovary; campylotropous ovules are at right angles to the funiculus; anatropous ovules are directed back toward the funiculus. Intermediate forms also occur.
  39. 39. TapetumPollen Sac
  40. 40. • Pollen/Pollen grains- formed inside the anthers, which are specialized parts of the stamens• Pollen sac- Each anther lobe contains two longitudinal pollen sacs (or locules) within which the pollen grains are produced. A single vascular band extends from the filament into the center of the connective and continues into the anther.• Tapetum-The sporogenous tissue is delineated from the anther wall by a single-layer of cells designated as the tapetum. The cells of the tapetum enlarge and develop a complex ultrastructure, which indicates that they become very active metabolically
  41. 41. • The process by which living organisms produce their offsprings for the continuity of the species• One of the most important characteristic of all living beings. It is the production of ones own kind.• The modes of reproduction vary according to individual species and available conditions.
  42. 42. How are new plants formed?New plants can grow in several ways:from seeds (sexual reproduction)- offspring is created by fusion of haploid gametes, the egg and sperm cells - new individual differs geneticallyFrom Bulbs, tubers and other vegetative parts (asexual reproduction)- creation of new individuals whose genes all come from one parent without fusion of egg and sperm. - e.g Budding, fission, sporulation and etc
  43. 43. Sexual reproduction Flowers contain a plant’s reproductive organs. Most plants contain both male and female parts. Some plants have only male sex organs while others contain only female sex organs. The organs may even be separate on the same plant (squash)
  44. 44.  Sexual reproduction needs special sex cells called gametes. The advantage of sexual reproduction is that it leads to genetic variation. If a species is varied it is more likely to be able to adapt to any changes in its surroundings.
  45. 45. In a flowering plant the flower develops on the receptacle.The buds of the flower are protected by sepals. Sepals are small leaves. The petals of many flowers are brightly colored which attracts insects.These petals are often highly scented. Inside the flower there are pin-like structures called stamens.
  46. 46.  The top of the stamen produces pollen or pollen grains, male gametophyte (microgametophyte). The club-like structure is the stigma. Pollen is produced by meiosis of microspore mother cells that are located along the inner edge of the anther sacs (microsporangia). The tube cells (tube nucleus) develop to pollen tube. The germ cells divides by mitosis to produce two sperm cells. Division of germ cell can occur before or after pollination
  47. 47.  In the base of the stigma is the ovary. The ovary contains ovules. Each ovule contains a female sex cell. The carpel is made up of the stigma, style and ovary. When the tip of the stigma is sticky it indicates that the carpel is ripe and ready to receive grains of pollen. Flowers differ in external colour, size and shape. However they all have a similar internal structure. Some have carpels with one ovule, others have rows of ovules.
  48. 48. THANK YOU!!!
  49. 49. Cont... It may be simply by division of the parent cell as in unicellular organisms, by fragmentation of the parent body, by formation of buds and spores,or it may be very elaborate involving development of male and female reproductive organs (stamens and pistils). Irrespective of the mode of reproduction, all organisms pass on their hereditary material to their offspring during the process of reproduction.
  50. 50. MODES OF REPRODUCTION The various modes by which plants reproduce are of three types – (a) Asexual (b) Vegetative (c) Sexual
  51. 51. • In Asexual mode of reproduction, offspring are reproduced from a vegetative unit-produced by a parent without any fusion of gametes or sex cells.– A single parent is involved– Offsprings are genetically identical to the parent.Asexual reproduction may be of the following types—• Fission : As in unicellular organisms like bacteria and yeast where the content of the parent cell divides into 2, 4 or 8 daughter cells and accordingly the fission is known as binary or multiple fission. Each newly formed daughter cell grows into a new organism.
  52. 52. Binary fission in bacteria
  53. 53.  Budding : A bud like outgrowth is formed on one side of the parent cell and soon it separates and grows into a new individual e.g. in yeast.
  54. 54.  Fragmentation : In filamentous algae, an accidental breaking of the filament into many fragments, each fragment may give rise to a new filament of the algae by cell division e.g. Spirogyra.
  55. 55.  Spore formation : In lower plants including bryophytes and pteridophytes, special reproductive units develop asexually on the parent body. These are called spores. They are microscopic and covered by protective wall. When they reach the suitable environment they develop into a new plant body e.g. in bread moulds, moss, fern.
  56. 56.  Vegetative reproduction : involves formation of new plantlets from vegetative-(somatic) cell, buds or organs of the plant. Here, a vegetative part of the plant (Root, stem, leaf or bud) gets detached from the parent body and grows into an independent daughter plant.-It is similar to a sexual reproduction in that it also requires only mitotic division, no gametic fusion and daughter plants are genetic clones of the parent plant.
  57. 57. • Stems, roots, leaves and even buds are variously modified to suit this requirement. This is called natural vegetative reproduction.• Natural Method : In natural methods, a portion of the plant gets detached from the body of the mother plant and grows into an independent plant. The parts may be stem, root, leaf or even flower.
  58. 58. Cont... The underground modification of stem, like rhizome, (in ginger), tuber (potato), bulb (onion) and corm (zamikand) are provided with buds which develop into a new plant Plants with sub-aerial modification such as Pistia (offset) and Chrysanthemum (sucker) are also used for vegetative propagation.
  59. 59. -tuberous roots (Asparagus and sweet potato) can also be used for propagation as these roots have adventitious buds which ground into a new plant.
  60. 60.  leaves contribute to propagation of plants leaves of Bryophyllum and Kalancloe have buds on the margin and these buds grow into small plantlets. When detached from the mother plant they grow into independent plants. Bryophyllum
  61. 61.  Agave and Oxalis multicellular bodies called bulbils develop near the flower. These are called bulbils which when fall on the ground grow into new plant. Agave bulbils Oxalis
  62. 62. ARTIFICIAL METHODS Cuttings : Many plants like rose, Bougainvillea, Croton, Coleus, money plants, sugarcane etc. are grown through their stem cuttings. Cuttings of these plants can be grown even in water where they strike roots and develop adventitious buds.
  63. 63. • Layering : In this method, a lower branch of a plant is bent down and covered with moist soil leaving the growing tip above the soil. A ring of bark is removed from the stem before it is bent down In a few weeks time when enough roots have developed on the underground portion above the ringed part, it is cut off from the parent plant and grown separately as an independent plant.• Example: Jasmine, straw berry, grapevine, Bougainvillea etc.
  64. 64. • Aerial layering or Goatee is a similar practice where bending of branches isn’t possible because of the height of plant or due to woody nature of stem. In this method a ring of bark is removed from a selected branch, and it is covered with moist moss and enclosed in a polythene sheet when roots appear, the stem is cut below the roots and planted to form a new plant.
  65. 65. • Grafting : It is especially important for propagation of seedless varieties of plants. It consists of inserting a small branch into a rooted plant.• The rooted plant taken as a stock is resistant to disease and is physically sturdy. In this stock a branch is inserted which is known as scion or graft. This scion or graft is the stem cutting from the desired plant. Usually the grafted end of stock and scion fit well with each other and are bound firmly with tape or rubber-band until their tissues unite and vascular continuity is established.• Grafting is mostly practised in dicot plants. Grafting has been found extremely useful in propagating improved varieties of various flowers and fruits like rose, Bougainvillea, Citrus, mango, apple etc.
  66. 66.  Tissue culture
  67. 67. • MICROPROPAGATION - The technique of plant tissues culture is utilised for propagation of plants.-A small piece of tissue, organ or even a single cell is taken from a plant and is transferred to a sterilized container with nutrient medium in aseptic conditions. The tissue grows very-very fast into an unorganised mass, called callus.-The callus can be maintained and multiplied for an indefinite period. When small portions of the tissue are transferred to another specialised medium with hormones, it induces differentiation and plantlets (little plants) are formed.-The plantlets can be transplanted into pots and or soil by a gradual process and are grown to mature plants.
  68. 68. Advantages of micropropagation By this method an indefinite number of identical plants can be obtained vegetatively starting from a small amount of parent tissue. In orchids, carnations, Chrysanthemum and Asparagus, micropropagation is being successfully tried in some parts of our country.
  69. 69. ADVANTAGES AND DISADVANTAGESOF VEGETATIVE REPRODUCTION• Advantages-Rapid means of reproduction and spread.- Offsprings identical to parent. The desired varieties can thus be preserved genetically for use.-Food storage organs allow perennation or survival in adverse conditions.-Improved varieties of ornamental plants and fruit trees can be multiplied easily.- Vegetative propagation is a quicker, easier and a less expensive method of multiplying plants.
  70. 70.  Disadvantages-Overcrowding and competition for space unless separated artificially.-New varieties cannot be produced by this method except by mutation.- Diseases typical of the species are rapidly transmitted and can decimate a crop.
  71. 71.  Sexual reproduction involves fusion of male and female reproductive cells-(gametes) which are haploid produced by male and female reproductive organs.-This fusion is known as fertilization and results in the production of a zygote (diploid). Further development of zygote gives rise to a new individual which is diploid.
  73. 73. • Angiosperms reproduce both by vegetative as well as by sexual methods. In this section we will study the sexual reproduction in angiosperms.• As you know sexual reproduction occurs by fusion of male and female gametes present in the flower.• Thus flower represents the reproductive unit of a plant.• Angiosperms can be classified as annuals, biennials and perennials depending upon the time they take to complete the life cycle and flowering.(a) Annuals eg. pea(b) Biennials e.g. radish(c) Perennials e.g. mango, peepal, neem etc.(d) Monocarpic e.g. bamboo
  74. 74. Factors Affecting Flowering Flowering in a plant is affected by temperature (vernalisation) and light(photoperiodism).Vernalisation : Low temperature treatment which stimulates early flower formation is called vernalisation.Photoperiodism : It is the response in growth and flowering of a plant to the duration of light and dark period per day.Sex in flowers : (flower, inflorescence, fruit and families), that flowers may be bisexual (having both stamens and carpels) or unisexual (staminate or pistillate).
  75. 75. Angiosperms: Production of Male Gametophyte Stamen = filament + anther Meiosis inside anther male spores Details follow
  76. 76. Angiosperms: Production of Male Gametophyte Meiosis in lily anther 4 haploid daughter cells, also called “pollen tetrads” Haploi Haploi d d Haploi Haploi
  77. 77. Angiosperms: Production of Male Gametophyte From the point of view of the plant life cycle, anther = male sporangium Each of the 4 pollen tetrads = spore Because of their small size, they are called “microspores”. Haploid Haploid Pollen tetrads = microspores Haploid Haploid
  78. 78. Angiosperms: Production of Male GametophyteHaploi Haploi d d As anther matures, 4 microspores of a tetrad separate from each other Haploi d Haploid nucleus of eachHaploi microspore undergoes a single d mitotic division Mitosis The 2 resulting haploid nuclei become encased in a thick, resistant wall, forming a pollen grain. Pollen Grain
  79. 79. Angiosperms: Production of Male GametophyteHaploi Haploi From the point of view of the d d angiosperm life cycle, a pollen grain is an immature male gametophyte, since it has been produced by the mitotic division of a spore. Haploi dHaploi d Mitosis Pollen Grain
  80. 80. Angiosperms: Production of Female Gametophyte The pistil (female reproductive portion) is composed of the stigma, style, and ovary.
  81. 81. Angiosperms: Production of Female Gametophyte An ovary may contain a number of ovules.Meiosis takes place inside the ovules, resulting in the production of femalespores. Details follow
  82. 82. Angiosperms: Female GametophyteOnly one of the haploid spores resulting from meiosis in the ovulematures. It undergoes 2 rounds of mitosis to form the “embryo sac”,which has 8 haploid nuclei. Embryo sac = female gametophyte
  83. 83. Alternation of Generations: Angiosperms To complete the life cycle, the gametes produced by the male and female gametophyte must unite, restoring the diploid sporophyte. Female gametophyte = embryo sac Immature male gametophyte = pollen grain
  84. 84.  Pollination : Transfer of pollen grains from the anther to the stigma of flower.
  85. 85. 1. Pollination by wind (Anemophily) : (Anemos : wind, Phile: to love)-example, grasses and some cacti.2. Pollination by insects (Entomophily) : (entomo : insect, phile : to love)-Salvia flowers show special adaptations for pollination by bees.3. Pollination by Water (Hydrophily) (Hydros : water)-e.g. Hydrilla, Vallisneria.4. Pollination by Animals (Zoophily) (Zoon : animal)-example sun bird, pollinates flowers of Canna, gladioli etc., Squirrels pollinate flowers of silk cotton tree.
  87. 87. Fertilization and Embryo Formation Pollen grain landing on stigma of ovary pollen tube growth
  88. 88. Fertilization and Embryo Formation 2 haploid cells of pollen grain are called the “generative cell” and the “tube cell” Pollen tube growing from a pollen grain
  89. 89. Fertilization and Embryo Formation As pollen tube grows towards ovule, nucleus of “generative cell” divides by mitosis, producing 2 haploid sperm
  90. 90. Fertilization and Embryo Formation The pollen grain, along with the pollen tube containing 2 sperm, is the mature male gametophyte.
  91. 91. Fertilization and Embryo Formation Pollen tube continues to grow, entering ovule through opening called the “micropyle”
  92. 92. Fertilization and Embryo Formation One of the sperm fertilizes the egg, producing a diploid zygote. This zygote will divide and differentiate, forming the sporophyte plant. The angiosperm life cycle has been completed. The other sperm will fuse with the 2 central haploid nuclei in the embryo sac, producing a triploid nucleus. These events are called “double fertilization”.
  93. 93. Fertilization and Embryo FormationTissue that develops from the triploid nucleus =“endosperm”. Energy stored in this tissue nourishes thedeveloping embryo.
  94. 94. “Don’t make me read, make me understand “ THANK YOU!!!
  95. 95. Flower Structure - review Ranunculus acris - buttercup
  96. 96. Flower Formula: Symbol Sequence to Diagram Flower Symmetry: *=radial †=bilateral * 5, 5, , 5 Number of Parts per Whorl: • sepals in calyx • petals in corolla • stamens in androecium • carpels in gynoecium Fusion within whorl: curved line over number Fusion between whorls: square bracket below numbers Attachment of flower parts relative to ovary: horizontal line