Plant Fertilisation

3.4 understand that the growth of the pollen tube followed by fertilization leads to seed and fruit formation.



Steps to plant fertilization

When the pollen grains land on the stigma they germinate and a tube form the pollen begins to grow in the stigma. This is species specific which means that pollen tubes will only complete if they are from the same species.
The pollen tube goes all the way down to the ovary. Then the male nucleus travels through the pollen tube.
Afterwards the pollen nucleus will fertilize the ovule, leading the the formation of a zygote which will grow into the / an embryonic plant.
The outside of the ovule forms a seed coat called the TESTA
There is also the formation of the cotyledons which are a food store that will support the plant before it develops it's first set of leaves.
A thickening of the walls of an ovary occur (The plant will put alot of energy into the ovary walls and things like sugars and protein will build them up which will form fruits (developed by the wall of ovary/carpel)

Pollination

3.3 a and b Describe the structures of an insect-pollinated and wind-pollinated flower and explain how each is adapted for pollination.

Insect Pollination

For pollination to occur there has to be a transfer of pollen grains from the anthers of one plant to the stigma of another plant.

A Pollen = A small structure which contains the male nuclei.

With insect pollination the transfer occurs through insects. Therefor it is necessary for one flower to attract an insect, the pollen attaches to the insect and the insect has to be attracted to the other flower for the pollen to be dropped off. 

Cross Pollination = When one Pollen form one plant is carried to another plant, this is called cross pollination.

The stamen = The male part of the plant which is composed of the anther, which produces the pollen grains and the filaments.

The Carpel = The female part of the plant which is composed of the Stigma which is connected to the ovary thorough the style. In the ovary you will find the eggs of a plant which are called the ovules.

How Flowers attract insects

Insects can see color and so colored petals attract them.

Flowers often have cents and so the insects can detect these molecules and are attracted.

Value to the insect. Value is things such as food (Nectaries) producing a sugar called Fructose.

Pollen is also used as a source of protein.

Wind Pollination

Wind pollination is the transfer of the pollen grains from the anther to the stigma carried through air by wind

We would expect the pollen grains and the plant structure to be like:
-Light weight
- Have a sort of wings feature to help it travel though the air more efficiently.
- The anther will be well clear from any basic flower structure so that they are well exposed to the wind.
- The stigmas will have a really large surface are and a feather like structure to catch the pollen the grains as they pass through the air
- There is no color in the petals and no cent and no nectaries because there is no need for this type of flower to attract insects

E.G