Plant Reproduction

FERTILISATION- Occurs when the male nucleus from the pollen grain fuses with the egg cell in the egg sac to prod' a zygote.

To get from the tip of the stigma to the egg sac-> pollen grain prod's a thin tube called the pollen tube.

The zygote develops quickly to form an embryo plant w/c needs t/b protected from drying out.

Embryo plant cont's tissues that will become roots, stem and leaves when it starts to germinate.

Carbohydrate, protein and lipid food stores (tissues) surround zygote = cotyledons 

Ovule wall hardens as zygote grows-> forms tough/hard protective casing around the seed= seed coat. Protects embryo as the seed passes thru animal's faeces and excreted.

Ovary tissue usually develops into a fruit. Fruits often have soft and sweet to attract animals to eat them.

GERMINATION- begins when the seed absorbs large amts of water.

The water acts as a solvent and provides right conditions for enzymes to start working. Warmth helps to increase rate of enzyme action. Cell resp' increases to release energy needed for growth.

Presence of light = not needed for germination-> most seeds are under ground, so can't get their food from photo'. 

1) Energy they need comes from breaking down food reserves in the cotyledons.

2) Usually, embryo root (radicle) starts to grow first so developing seedling can get more water.

3) Shoot starts to grow, In some plants the cotyledons are lifted above ground as shoot grows-> become seedling leaves.

4) Other plants leave the coty' below ground and photo' does not begin until first real leaves develop.