Having thought about controlling variables, another variable that I could not control is the fact that different sides of the hedge would have been more exposed to the natural elements e.g. the wind and the rain.
Although a higher light intensity could make the leaf's surface area larger, I now also think that a lower light intensity could make the leaf's surface area larger. This could happen, as to make the rate of photosynthesis efficient with only a low light intensity, there would have to be a large number of chloroplasts containing chlorophyll to absorb the light intensity available, meaning the surface area would have to be larger to get all the light possible.
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