Are there more stomata per mm2 on old leaves or young leaves?

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Are there more stomata per mm2 on old leaves or young leaves?

Planning

Equipment

Leaves (old and young)

Clear nail-varnish

Microscope

Lamp

Forceps

Slide

Graticule (1cm)

Method

I will take some old leaves and some young leaves. I aim to use three of each. I think this is a realistic amount to use because it is a slow process. The leaves I will use will be from a cherry laurel bush (prunus laurocerasus). I will know which leaves are young and which are old by their colour and size. Young leaves are small and a lighter green. Old leaves are larger, and a darker green. First, I will clean the leaf, to remove dust and dirt. Then I will paint 1cm2 of clear nail-varnish on the underside of the leaf, because that is where the stomata are. I will paint the nail-varnish to one side of the mid-rib, but not too near the edge. I will then leave it to dry, while I measure the size of the microscope's field of view, on medium power. To do this, I will use the graticule to measure its diameter, then divide this in half to find the radius. Then I will use the radius measurement in the formula ?r2 to work out the area of the field of view. When the nail-varnish is fully dry, I will carefully peel it off with a pair of forceps, and place it on a slide the same way up as it was on the leaf. Then I will look at it under the microscope. It will be a perfect imprint of the underside of the leaf. I will count the number of stomata I can see in the field of view, and use the area of the field of view to work out how many stomata there are per mm2. I will repeat this process with all of the leaves.

Controls and variables

The only variable in my experiment will be the age of the leaf. I will try to ensure that all the other conditions remain the same.

* I will make sure that all the young leaves are the same size, and all the old leaves are the same size. This will mean that there will not be a range of ages.

* I will put the nail varnish on the same part of the leaf, as the number of stomata may vary, according to where they are on the leaf.
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* I will keep the same nail varnish at the same thickness, so they all peel off in the same way.

* I will always use the same magnification - medium power, so that the field of view will remain constant.

* I will choose leaves from the same side of the same bush, so that all the leaves will have developed in the same conditions.

* I will not distort the nail-varnish peel by pressing down on it, changing the results.

Prediction

I think that age does not affect the amount ...

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