FLOWERS

• Flowers are the reproductive organ of flowering plants
• Flowers specialize in sexual reproduction
• Flowers arise from the axil of the leaf
• A typical complete flower consists of 4 whorls:

  • Outer whorl: calyx
  • Next: corolla
  • Inner whorls: essential organs (stamen and pistils)
• 6. Corolla - the collective term for all petals, usually thin, soft, and colored to attract animals for pollination

  7. Perianth - the collective term for all petals and sepals

  8. Pistil (Carpel) - the seed-bearing organ of the flower, usually pear-shaped and found at the center of the flower, composed of the ovary, style, and stigma
• Parts of a typical flower:

  1. Pedicel - the stalk that holds the flower

  2. Receptacle - somewhat enlarged tip of the pedicel from which the floral parts arise

  3. Sepal - one of the several leaf-like structures that make up the outermost circle of the floral parts. It is usually green in color and protects the flower while it is still a bud

  4. Calyx - the collective term for all sepals, typically green but can be petal-like in some species

  5. Petal - one of the colored leaf-like structures that occurs in one or more circles within the sepals
• Ovary - the enlarged basal part of the pistil, can have one or more locules (cavities) containing ovules that develop into seeds after fertilization

  • Ovules are small, round or oval-shaped bodies inside the locules of the ovary, containing the egg cell and other related cells
  • Locule is the cavity within the ovary
• Style - long and slender neck-like part extending from the ovary, serving as a passageway for pollen from the stigma to the ovary
• Stigma - sticky part found at the tip of the style to which the pollen adheres after pollination
• Stamen - the essential male part of the flower consisting of an anther and a filament

  • Anther is where pollen grains are produced, supported by the slender filament and usually consists of four pollen sacs
  • Filament is the slender stalk that supports the anther
• Classification of flowers based on the presence or absence of floral parts:

  • Complete flower: has all four essential floral parts
  • Incomplete flower: lacks one or more of the four floral parts
  • Perfect flower: has both stamen and pistil, may lack sepals and petals
  • Imperfect flower: bears either the stamen or pistil, may be staminate or pistillate
• Symmetry of flowers:

  • Radial symmetry: divisible on more than one axis into two equal halves that are mirror images of each other
  • Bilateral symmetry: divisible into right and left sides, mirror images on only one axis
• Position of the ovary:

  • Perigynous: ovary is half-interior but the bases of the stamens, petals, and sepals develop as a floral cup around the ovary
  • Hypogynous: ovary is superior, with the stamens, petals, and sepals arising from a level below the base of the ovary
  • Epigynous: ovary is inferior, with the stamens, petals, and sepals arising from a level above the base of the ovary
• Placentation:

  • Marginal: ovules are attached to vertical rows along the ovary wall
  • Parietal: in a compound pistil, the carpels are joined margin to margin and the placenta is situated on the ovary walls
  • Basal: found in both simple and compound carpels, with one locule in the ovary, the ovule is attached to the base of the ovary
  • Axile: the ovules are attached to the middle of the ovary, where the septae of a compound pistil are joined
• Fusion of the floral parts:

  • Adnation: unlike parts like petals and sepals are fused
  • Connation: like parts are fused, as in petals of Anthurium
• Kinds of inflorescence:

  • Spadix: a spike with a fleshy axis, enclosed by a large, often brightly-colored bract called spathe
  • Spike: elongated axis with flowers that are sessile or without a stalk
  • Catkin: a spike with a long and pendulous axis, bearing unisexual flowers only
  • Raceme: elongated axis bearing a number of flowers, all stalked, with lower flowers having longer stalks than the upper
• Other types of inflorescence:

  • Panicle: main axis of the flower is branched, and the lateral branches bear the stalked flowers
  • Cyme: the main axis ends in a flower that opens before the flowers below or on its side open, further growth takes place with the growth of one or more laterals
  • Umbel: the primary axis bears a group of flowers at its tip with pedicles of more or less equal lengths
  • Corymb: the main axis is short, lower flowers have longer stalks than the upper ones
• • Capitulum or head: the main axis is almost flat, composed of ray flowers along the margin and disk flowers crowded at the center
• Sexual reproduction in flowering plants:

  • Stamen consists of an anther and a filament
  • Pistil consists of the ovary, style, and stigma
  • Dicot flowers usually have four or five floral parts, while monocot flowers usually have three floral parts
• Pollination:

  • Self-pollination: transfer of pollen from the stamen to the stigma of the same flower
  • Cross-pollination: transfer of pollen from the anther to the stigma of flowers found in separate plants
• Ovule:

  • Protruding masses of tissues contained in the ovary, develop into seeds after fertilization
  • Funiculus is the stalk where the ovule is attached, found at the region called placenta
• Types of plants based on flower structure:

  • Monoecious: both male and female flowers are found on one plant
  • Dioecious: stamen and pistil are on different plants, requiring cross-pollination between separate plants
• Examples of flowers mentioned in the text:

  • Anthurum
  • Sunflower
  • Calla lily
  • Daisy
  • Rose
  • Santan
  • Gumamela