Hello, I am measuring stomatal index in WT and mutant arabidopsis plant. The formula for SI says to divide the stomatal number by total number of stomata+epidermal cells. I am bit confused on how to count the epidermal cells, should I count only those that are entirely visible in my image or all the cells irrespective of their completeness? My mutant has bigger cell size, so if i count only the entire epidermal cells that are present in the image it is going to affect the stomatal index. Thanks.
Hello, Anamika,
Stomatal index is a measure of stomataldensity on the leaf surface. It is calculated by dividing the number of stomata by the number of epidermal cells in a given area. Itcan be used to assess the water status of a plant, as well as its photosynthetic efficiency.
To calculatestomatal index count the total number of stomata in the observed area. Then, count the number of epidermal cells in the same area.
Now calculate the stomatal index using the following formula:
Stomatal Index = (Number of stomata / Number of epidermal cells) x 100.
Hope it will help.
To be more accurate, especially with the mutant that has larger epidermal cells, you can do one of two things: 1) decrease the magnification for the mutant with the larger cells so fewer cells will be cut off in the field of view; or 2) for the cells that are cut off at the edge of the field of view, approximate how much of each cell is in the field, then add those fractions of a cell to your total number of cells.
I think you would count also partial cells, but only along 2 adjacent sides (like only left and upper edge of the image) for all images and genotypes (see this paper: Kubínová, L. (1994). Recent stereological methods for measuring leaf anatomical characteristics: estimation of the number and sizes of stomata and mesophyll cells. Journal of Experimental Botany, 45(1), 119–127. doi:10.1093/jxb/45.1.119
thanks everyone for your clearing my doubts and for useful suggestions. I am going to combine strategies suggest by Edward Bobich and Daniela Liebsch to see what comes out. Thanks again for time :)
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