Question

Stomatal index is equal to:
A.\[\dfrac{S}{E-S}\]
B.\[\dfrac{S}{E+S}\]
C.\[\dfrac{E}{E+S}\]
D.\[\dfrac{E+S}{E}\]

Answer 1

Hint: Stomata are the minute pares which are generally present on the lower surface of the leaves which helps in transpiration (evaporation or removal of excess water through leaves).

Complete answer
Besides the loss of water vapour in transpiration exchange of Oxygen and Carbon dioxide takes place also through stomatal pores. Stomata are found open during daytime and closed at night.
The lower face of dicotyledons have greater number of stomata while Monocotyledons have equal number of stomata on both surfaces.
Stomatal index (I) is calculated as follows.
Stomatal index (I) \[=\dfrac{No.\,of\,stomata\,per\,unit\,area(S)}{No.\,of\,stomata\,per\,unit\,area+\,No.\,of\,epidermal\,cells}\]
i.e.
\[=\dfrac{S}{E+\,S}\]

So the correct option is option (B).

Note:Stomatal index is used to compensate for the differences in stomatal density e between Sun and shade leaves wet and dry climate leaves of the same species.