Plant Fertilisation Practice Test

Plant Fertilisation

- When the pollen grain sticks to the stigma, it begins to germinate causing a tube to grow named a pollen tube. It descends down the stigma, through the carpel and into the ovule. Each pollen grain has its own pollen tube.

- The pollen nucleus fertilises the ovule, which will lead to the formation of a zygote. This will then turn into the embryonic plant.  In addition to this Cotyledons are formed, which are food stores for the seedling. They support the plant until it develops its first set of leaves.

- The outside of the ovule forms a seed coat, or a TESTA

- Another thing that occurs, is the thickening of the walls of the ovary/carpel. The plant will put energy into building up sugars and proteins in the ovaries/carpel, which produces fruit.

Wind Pollination

- For the process of pollinating a flower there has to be a transfer of pollen grains from the anthers of one plant to the stigma of another, through air carried by the wind.

- In wind pollination it is unnecessary for the plant to have a nice appearance and scent because it doesn't need to attract insects. Because of this it has no nectaries because that would be a waste of energy. The wind moves the pollen from the anther of one plant to the stigma of another.

- First adaptation to have light pollen grains, possibly a wing feature to help them glide through the air efficiently. 

- Second adaptation is to have anthers that hang well away from the basic flower structure to expose them to the wind more. This is so it is easy for the wind to pick up the pollen grains.

- Third adaptation is for the stigma to have a large surface area, similar to the end of a feather.

Insect Pollination

- For the process of pollinating a flower there has to be a transfer of pollen grains from the anthers of one plant to the stigma of another. This is known as Cross Pollination.

- Pollen contains the male nuclei, and is transferred to the stigma of other plants by insects.

- Because of this it is necessary for the plant to attract insects to it. It does this by either making itself look appealing (coloured petals - insects react well to this), or smelling good. Also a value to the insect of going to the flower, which is provided using food by the nectaries. The nectaries produce fructose which the insect uses as a source of protein.