Reproduction

• Style


  Elongated slender part beneath the stigma
• Ovary


  Basal bulged part of the pistil
• Ovarian cavity (locule)


  Made within the ovary
• Placenta


  Located inside the ovarian cavity
• Megasporangia


  Arising from the placenta
• Pollen grains


  • Rich in nutrients
  • Used as food
  • Claimed to increase performance of athletes and race horses
• When pollen grains are shed, they have to land on the stigma before they lose viability if they have to bring about fertilisation
• Pollen viability period

  Highly variable and depends on temperature and humidity
• Pollen grains of some cereals like rice and wheat lose viability within 30 minutes of release, while some members of Rosaceae, Leguminoseae and Solanaceae maintain viability for months
• Pollen grains of many species can be stored for years in liquid nitrogen (-196°C) and used as pollen banks in crop breeding programmes
• Gynoecium


  Female reproductive part of the flower
• Pistil


  Single unit of the gynoecium
• Pistil

  • May be single (monocarpellary) or more than one (multicarpellary)
  • May be fused together (syncarpous) or free (apocarpous)
• Stigma


  Landing platform for pollen grains
• Style


  Elongated slender part of the pistil
• Ovary


  Basal part of the pistil
• Ovule


  Small structure attached to the placenta by a stalk called funicle
• Hilum


  Junction between ovule and funicle
• Integuments


  Protective envelopes encircling the nucellus except at the micropyle
• Micropyle


  Small opening in the integuments
• Chalaza


  Basal part of the ovule, opposite the micropylar end
• Nucellus


  Mass of cells enclosed within the integuments
• Embryo sac

  Female gametophyte located in the nucellus
• Megasporogenesis


  Formation of megaspores from the megaspore mother cell
• Megaspore mother cell (MMC)


  Large cell with dense cytoplasm and prominent nucleus, located in the micropylar region of the nucellus
• Meiosis of MMC

  Results in production of four megaspores
• Functional megaspore

  Develops into the female gametophyte (embryo sac)
• In majority of flowering plants, only one of the megaspores is functional while the other three degenerate
• The mature embryo sac has 7 cells and 8 nuclei
• Pollination


  Transfer of pollen grains from the anther to the stigma
• Types of pollination

  • Autogamy
  • Geitonogamy
  • Xenogamy
• Autogamy


  Pollination within the same flower
• Geitonogamy


  Pollination between flowers of the same plant
• Xenogamy


  Pollination between flowers of different plants
• Synergids


  Cells grouped together at the chalazal end of the egg apparatus
• Egg cell

  One of the cells within the egg apparatus
• Pollination


  Transfer of pollen grains shed on the anther to the stigma of a flower
• Types of pollination

  • Autogamy
  • Geitonogamy
  • Chasmogamy
• Autogamy


  Pollination achieved within the same flower, transfer of pollen grains from the anther to the stigma of the same flower
• Geitonogamy


  Transfer of pollen grains from the anther to the stigma of another flower on the same plant