PLANT FERTILISATION

          growth of pollen tube
pollen grains on the sigma germinate and a tube begins to grow downwards towards the ovule.
this tube is called the pollen tube.
the male nucleas from the pollen grain uses this tube to travel down and into the ovule.

          fertilisation
when the male nucleas travels down and into the ovule it fertilises the ovule.
this leads to the formation of the zygote which grows into the embryonic plant.

          seed formation
the outside of the ovule turns into the seed coat or testa
the testa not only holds the zygote which is the embryonic plant but it also contains the cotyledons which are food stores which will support the plant until it grows leaves and is able to make their own food.

          fruit formation 
the thickening of the walls of the ovary (carpel) combined with sugar and protein that the plant gives up forms the fruit.

Wind Pollination

wind pollination
transfer of pollen grains through wind

anther ----air/wind----> stigma

adaptations to suit this type of pollination
- light weight
- wing features to allow it to move in the air/wind more efficiently
- Anthers stick out far from flower so it is exposed to the wind therefore can be carried away easily
- Stigmas will stick out far from the flower and has a large surface area so that it can catch pollen grains as they pass through the air.

these plants do not need to attract insects therefore it will not have colour, scent or nectaries.

Insect Pollination

pollen --> is a small structure which contains the male nuleu
pollination --> transfer of pollen from an anther to the stigma.
cross pollination --> when pollen goes from one plant to another it is called cross pollination

insect pollination --> is pollination that takes place by insects
therefore it is necessary for the plant to attract insects
factors that make the plant attract insects:
- coloured petals
-scented
- value for the insect - the plant contains food for insects such as nectaries which produces fructose sugar and pollen which for some plants is a source of protein.