Different types of seeds

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3.4 Plant Fertilisation

-Pollen grain germinates and tubes starts to grow.
-This is species specific (the tubes will only complete if its the same specie)
-The pollen tube tubes go all the way down to the ovule, the male nucleus travels through the pollen tube into the ovule
1) Pollen nucleus will fertilize the ovule ------------->  leads to a formation of a Zygote
                       -This will grow into the embryonic plant
2) Outside of the ovule forms a seed coat which is called a testa
3) Inside the ovule you get the formation of the cotyledons
                      -These are food stores for the 'seedlings'. This will support the plant until it grows/devalops leaves
4) Thickening of the walls of the ovary. This will build up sugars and proteins which will form the fruit which is developed from the wall of the ovary

3.3a,b - Pollination

A plant consists of:
female part (carpel) which consists of the stigma, style, and the ovary
Male part (staman) which consists of the filaments and the anther


Insect pollination
-There has to be a transfer of pollen from the anther of a plant to the stigma of another plant (cross-pollination
(The pollen contains the 'male' nuclei)
-This takes place because of insects

-For this to happen the insects have to be attracted to the flower.
                                                         To attract an insect, the plant uses:
                                        -Signals --- Coloured petals
                                                     --- Scents (smell)
                                        -Value   --- food (in nectaries) - Fructose
                                                     --- Some insects eat pollen as a source of protein

Wind pollination:
                                    air
                   Anther ----------> stigma
                                  wind

The pollen has to be:
-Light weight
-Has some 'wing' feature which moves the pollen more efficiently

-The anther sticks out from the main parts of the flower so that it is exposed to the wind
-The stigma has a large surface area (featherlike structure) to catch the pollen grains as they move through the air.
- The plant has nothing to attract insects because it is a waste of energy