Formula for calculating the leaf area of lettuca?

Answer 1

ANSWER 1

Since this is an irregular surface, you will have to use integration techniques: for example, divide the surface into many narrow strips, consider each strip to be a rectangle and calculate its area as such, add all up. The more narrow you make the strips, the more accurate will be your estimate.

ANSWER 2

The best method depends on the accuracy required of your measurements. If you require accurate and precise results, use a scientific instrument that's specially designed to measure the area of leaves. E.g. AM300 Leaf Area Meter

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My AM300 can store the image, and will analyse it to measure all sorts of useful parameters, like perimeter. I need a lightweight instrument which I can carry for hours, and it only weighs 1.8kg . Other models which are called 'portable' weigh 6.8kg!

If you do not require a high degree of accuracy, you can use the method described in ANSWER 1. However, you may find it quicker to draw around the leaf, then cut out and weigh the paper. By comparison to the weight of a known area of the same paper, you can calculate the area of the leaf. However, when using methods which involve cutting paper, you must cut around the perimeter extremely carefully. Similarly, you must be highly accurate when weighing. I am not sure that paper - even heavy paper - is heavy enough to make the relative error <0.5%.

You can opt for a method where you draw around the leaf on graph paper, then estimate how many grid squares are included in the area. However, grid squares that are partly included in the area must be approximated so introduce inaccuracies.

I have used software called imageJ to draw an irregular polygon on a photo of my leaf. I investigated C.hirsuta leaves, which are a similar size toArabidopsis, so it was possible to click a enough points on the image to accurately trace the perimeter, without it taking hours. To trace the perimeter of a larger leaf, you will have to make hundreds of clicks. By my experience, this will take a morning per leaf!