Experiment on Stomatal Index and Stomatal Frequency

Stomata are defined as the minute pores present on leaves and young shoots. Their main function is to facilitate gaseous exchange and transpiration. Algae and submerged plants do not exhibit the presence of stomata. In this article, we will be discussing the experimental calculation of the stomatal index and stomatal frequency.

Introduction

The two specialised epidermal cells which surround the stomatal aperture are called guard cells. Guard cells are kidney-shaped in the case of dicotyledons and are dumb-bell shaped in monocotyledons. Guard cells are further surrounded by some accessory cells called subsidiary cells.

Based on the stomatal index and stomatal frequency which give an idea about stomatal distribution, leaves can be of 3 types-

1. Hypostomatous type– The leaves where stomata are more frequently found on the lower surface of the leaves. Eg. Apple, Mulberry etc
2. Amphistomatous type– The leaves where stomata are equally distributed on upper and lower leaf surfaces. Eg. Maize, Oats etc
3. Epistomatous type– The leaves where stomata are only on the upper surface of the leaf. Eg. Nymphaea

Calculation of Stomatal Index and Stomatal Frequency

The stomatal index relates the number of stomata to the number of epidermal cells. It is defined as the percentage number of stomata as compared to all epidermal cells. Under a given set of conditions, this value is found to be reasonably constant for any particular species.

Stomatal frequency is the number of stomata in a definite area of the leaf that varies from plant to plant. Several environmental and genetic factors affect stomatal frequency.

Please check the videos for the procedure and calculation of the stomatal index and stomatal frequency.

Precautions

1. Don’t take the peel from the midrib, apex and base of the leaf.
2. Peels should be taken from the same leaf.
3. The magnification of the microscope should remain constant throughout the experiment.
4. Peels should be one-celled thick.

Also check out: Study of Stomatal Distribution on Leaves – MeitY OLabs – YouTube

Worth reading: How to use a Glucometer at home? – My Biology Dictionary