Plant Reproduction, Fertilisation and Pollination    (Worksheet 4)   Answers

Carpel is the name given to the female parts of the flower. These are the stigma, the style and the ovary. Stamen is the name given to the male parts of the flower. These are the anther, the pollen grains and the filament.

The anther produces pollen grains, which are the male sex cell. These pollen grains (through pollination) will land on the stigma of a flower and grow a pollen tube through the style to the ovule (the female sex cell) within the ovary.

Once the pollen tube reaches the ovule, a nucleus of the male cell can fuse with a nucleus in the female cell allowing fertilisation to occur. Then the ovary turns into a fruit and the ovule will grow into a seed.

The way in which a pollen grain is transferred to a stigma is called Pollination. It is interesting to note that plants can either self-pollinate (pollen grain transfers to the stigma of the same plant) or cross-pollinate (pollen grain transfer to stigma of another plant).

When cross-pollination occurs the pollen grain must obviously be moved to another area where it can attach itself to a stigma. Cross-pollination occurs in two ways - either by wind or by insects.

In order to attract insects to carry the pollen grains away, flowers normally have bright coloured petals to draw the insects in. The pollen grains are sticky and stick to the legs of insects that then carry the grains away where they will attach to the stigma (which is also sticky). Flowers that depend on insect pollination have other ways of attracting insects such as scented flowers or sugary nectar.

Flowers that are dependent on wind pollination have no need to attract insects. Hence the petals on these flowers tend to be not so brightly coloured and generally have no scent or nectar. However in order to have the best possible chance of pollination, these plants will tend to have long filaments which allow the anther to hang outside of the flower so that the wind can catch and carry the pollen grains to a stigma.
 

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