Stomata are located on the abaxial surface (underside) of leaves. They are part of the epidermal tissue. Stomata are important in gas exchange and transpiration. Carbon dioxide enters the leaf through the stomata. This carbon dioxide is used in the process of photosynthesis to manufacture carbohydrates. Transpiration refers to the process of water exiting the leaf through the stomata. This helps to cool the leaf and provides a gradient to move water from the roots up into the vine.

 

Impression of abaxial leaf surface using nail polish peel technique (polarized light)

 

 

A stoma is composed of a pore surrounded by two guard cells (red arrow in image at left). The guard cells adjust the aperture of the pore. When the guard cells become turgid, the pore is opened and gas exchange and transpiration can occur. As the guard cells lose their turgidity, the pore becomes closed.

 

Impression of leaf abaxial surface using nail polish peel technique (polarized light)