• Evolution seems to favour (and be favoured by) genetic variability. Genetic variability is promoted by out breeding (sexual reproduction between genetically dissimilar parents)
    • Sexual reproduction is so popular throughout the world of living things is still a hotly-debated question, but the fact remains. Plants, being anchored in position, have a special problem in this regard
    • Many employ the services of animals (e.g., insects, birds, bats) to transfer pollen from plant to plant.
    • But if the flowers have both sex organs: anthers producing pollen (the source of the male gametes) and the pistil producing the egg (the female gamete).


    • The imperfect flowers are present on separate plants
    • Dioecy is the equivalent of the separate sexes of most animals. But it is rather rare
    • Some examples
      • Poplars
      • Hollies


    • The imperfect flowers are present on the same plant
    • But if they mature at different times, self-fertilization is avoided
    • Cucurbits are common example

Last modified: Sunday, 1 April 2012, 9:25 PM