Investigating the Amount of Stomata on a Variety of Different Sized Leaves

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Investigating the Amount of Stomata on a Variety of Different Sized Leaves


During this experiment I am going to investigate the stomata on a large leaf and a small leaf from the same plant to compare the amount of stomata per mm². The stomata are small openings found in the lower epidermis of leaves. Each stoma is surrounded by two bean-shaped guard cells containing chloroplasts. A stoma is a very efficient structure because it can control the rate of transpiration (water loss) and the exchange of gases. When it closes, no transpiration occurs. When it opens, transpiration takes place. The stomata open to allow carbon dioxide into the leaf for photosynthesis and to allow oxygen out.
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The thin outer walls lose pressure which causes the thick inner walls to close, meaning the stoma is now closed and now more water is lost, therefore controlling the balance of water within a leaf.


I predict that the bigger leaves will have more stomata because it is the bigger leaves that help most during photosynthesis. The smaller leaves are not as important therefore they will not need as many stomata per mm². The bigger leaves are more important to the plant as they have a larger surface area which means that they can absorb much more sunlight than the smaller leaves, therefore they need more stomata to control the water levels. I think that the number of stomata per mm² in each size of leaf will vary quite a bit because I think that the younger leaf will not need near as many of stomata as the younger leaf as I think that transpiration is less important to a younger leaf.


1. First of all I am going to collect two leaves from the same plant. The leaves I will use are from the plant Tradascantia. I am going to obtain a larger leaf and a smaller leaf enabling me to compare them.

2. I am then going to use clear nail polish to paint a thick layer of varnish on the underside of the leaf. I am going to paint 5 dots which will give me a wider
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