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biology 0610printed 209 · PDF 209
328 pagesrevision 46933
printed 209 · PDF 209
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● The anthers have pollen sacs in them. Cells around the pollen sacs divide to
form the pollen grains.
● Pollen grains look like fine powder and are often yellow. Pollen grains from
different kinds of flowers have different shapes and can be spiky or smooth.
Each grain has an outer hard coating which protects it in difficult conditions.
Pollination
● For fertilization to take place the male gametes must travel to the female
gametes. The first stage of this journey is for pollen to be taken from the
anther where it was made a stigma. This is called pollination.
● There are two types of pollination.
● First is insect pollination. Insects come to flowers attracted by their color
and a strong sweet scent. The bee follows the guidelines to the nectaries,
brushing past the anthers as it goes. Some of the pollen sticks to its body.
The bee then goes to another flower in search of nectar. Some of the pollen
then sticks onto the stigma of the second flower when the bee brushes past it.
If the second flower is of the same species pollination has occurred.
● In some plants wind pollination occurs. Wind pollinated flowers usually
produce much more pollen than insect pollinated flowers as a lot of the pollen
does not land on flowers and is wasted. Wind pollinated flowers usually do
not have petals as there is no need to attract insects. Their anthers and
stigmas dangle outside the flower to catch the wind.