Study of distribution of stomata

Objective

Our objective is to study the stomatal distribution on the upper and lower leaf surfaces and to calculate the stomatal index.

Theory

What is a Stomata?

Stomata are minute pores found on the epidermis of leaves and young shoots of plants that are used to control exchange of gases. The pore is surrounded by a pair of specialised cells called the guard cells that are responsible in regulating the size of the opening.

Water is released through the stomata into the atmosphere in the form of water vapour through the process called transpiration. Besides this, the exchange of oxygen and carbon dioxide in the leaf also occurs through the stomata.

Distribution of Stomata

Distribution of stomata varies between monocots and dicots, between plant species, and between the underside and top side of the leaves on a plant. 

Stomata are found more on plant surfaces thriving under higher light, lower atmospheric carbon dioxide concentrations and in moist environments.

Usually the lower surface of a dicot leaf has a greater number of stomata while in a monocot leaf they are more or less equal on both surfaces. In most of the floating plants, stomata are found only on the upper epidermis.

Calculation of Stomatal Index

The distribution of stomata on the upper and lower surfaces of the leaf can be studied by removing the peels of the leaf from the upper and lower surfaces and observing the same under a microscope.

The count of the the number of stomata and epidermal cells in the microscopic field is taken  and the stomatal index of each surface of the leaf can be calculated using the following formula:

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Learning Outcomes

  • Students get to know what a Stomata is.
  • Students understand the distribution of stomata on different plants.
  • Students learn how to calculate the stomatal index.
  • Students will be able to do the experiment more accurately in the real lab once they understand the steps through the animation and simulation.

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