exchanging substances part 3

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the structure of leaves lets gases diffuse in and out of cells.

1) carbon dioxide diffuses into the air spaces within the leaf, then it diffuses into the cells where photosynthesis happens. the leafs structure is adapted so that this can happen easily.

2) the underneath of the leaf is an exchange surface. its covered in little holes called stomata which the carbon dioxide diffuses in through. 

3) oxygen and water vapour diffuse out through the stomata. 

4) the size of the stomata are controlled by guard cells. these close the stomata if the plant is losing water faster than it is being replaced by the roots. without the guard cells the plant will soon wilt. 

5) the flattened shape of the leaf increases the area of this exchange surface so that its more efective. 

6) the walls…

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