Dicotyledonous Plants e.g Petunia

• perianth in dicotyledonous flowers is differentiated into two parts: calyx and corolla
• The flower Petunia therefore consists of four whorls (rings of floral parts)

  Calyx

  Corolla

  Androecium

  Gynoecium
• Structure of a Petunia Flower

  
• Calyx


  Outermost whorl consists of five small, green sepals

  • sepals surrounded the other whorls and protected the flower in the bud stage
• Corolla

  Whorl consists of five, striking, brightly coloured petals fused together to form a trumpet-shaped corolla

  • petals attract insects and birds to flower for pollination
• Androecium (stamens)


  whorl composes male parts of the flower

  • Petunia has five stamens attached to the inside of petals
  • each stamen consists of a long filament ending in lobed anther
  • anther contains pollen sacs in which pollen is formed

  
• Gynoecium (pistils)

  Innermost whorl is the female part of the flower

  • consists of a single stigma, thin style and ovary
  • surface of stigma is sticky so pollen grain sticks to it
  • ovary contains two locules (small cavities) with large number of ovules
  • ovules are attached to separating well between the lobes
  • ovary is above the place of attachment of sepals, petals, stamens as the base of flower and if known as a superior ovary