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16.3) Sexual reproduction in plants

16.3) Sexual reproduction in plants

 

  • In the flower of most plants there are both stamen (male organs) and carpels (female organs), this is a condition known as bisexual or hermaphrodite.
  • Some plants have unisexual flowers.

 

Insect-pollinated flowers:

Wind-pollinated flowers:

  • Grasses have wind-pollinated flowers.
  • They have small petals, and their stamens and stigmas hang outside the flower.

Pollination: is the transfer of pollen grains from the anther to the stigma.

 

Self-pollination: is the transfer of pollen grains from the anther of a flower to the stigma of the same flower, or a different flower on the same plant.

  • No variation.
  • Not be able to adapt to changing environmental conditions.
  • No reliance on pollinators.

 

Cross-pollination: is the transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species.

  • Guarantee variation.
  • Better chance of adapting to changing conditions.
  • Reliance on pollinators to carry the pollen to other plants.

Fertilisation:

  • When a pollen grain lands on the stigma of a flower of the correct species, a pollen tube begins to grow.
  • It grows down the style and into the ovary, where it enters a small hole, the micropyle, in an ovule.
  • The nucleus of the pollen then passes along the pollen tube and fuses with the nucleus of the ovule.
  • This process is called fertilisation.

 

Environmental conditions that affect germination of seeds:

Germination is a process, controlled by enzymes, in which the seed begins to develop into a new young plant. Three main factors are needed for successful germination.

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