3.4 Plant Fertilisation

3.4 Plant fertilisation

Understand that the growth of the pollen tube followed by fertilisation leads to seed and fruit formation

The pollen grains (on the stigma) germinate and a tube known as the pollen tube grows descending down to the ovule. (The male nucleus travels down there into the ovule)

1.(Fertilisation) Pollen nucleus fertilises the ovule, this forms a

ZYGOTE which grows to become an embryonic plant.

Picture evidence in response to 3.3a

3.3a Insect Pollination

3.3a Insect pollination - Describe the structures of an insect pollinated flower and explain how it is adapted for pollination

The process of pollination:

·         In a flower pollen grains are transferred from the anther of one flower to the stigma of another flower.

(Pollen is a structure containing the male nuclei)

·         The transfer takes place by insects; therefore it is necessary to attract insects. The transfer of pollen from one plant to another is called cross pollination.

·         Adaptations to attract insects

1) Signal to the insects by the use of coloured petals

2) Scents; insects can detect the scent of the flower

3) Value is provided in the form of food

·         Nectaries produce a sugar called fructose. Pollen acts as a source of protein

·         In a petal it contains the:

Male parts:                                                                                                                        

Stamen

Anther (pollen grains)

Filament (stalk)

Female parts:

Stigma 

Style (connect to the stigma)

Ovary (contains ovules)

The whole structure is known as the CARPEL

3.3b Wind Pollination

3.3b Wind pollination - Describe the structure of a wind pollinated flower and explain how it is adapted for pollination

·         Wind pollination is the transfer from the anther to the stigma through the air

·         Pollen grain adaptation

1) Lightweight

2) Wing feature to easily allow them to move through the air

3) Anther- hang clear from any large structure, therefore it can be exposed to wind

4) Stigma- large surface area, featherlike structure-exposed to wind in order to catch pollen grains so that the anther can be caught on to it

·         Since the wind is pollinating the plant, no insects need to be attracted to the flower therefore the flower does not need any:

      -colour

      -scent

      -nectaries

      -production of sugar