PARENCHYMA CELLS, GUARD CELLS

Tradescantia Leaf

The epidermis is the outermost primary cell layer of a plant and usually is only one cell layer thick. The structure of this tissue system is related to its position on the plant, i.e. it is the tissue in contact with the exterior environment. Since the nature of this environment is different for a leaf, a stem, or a root, the epidermis varies accordingly. Here you can see the epidermal peel of Tradescantia.

 

 

 

 

 

 

 

 

The stoma refers to the hole in between the two guard cells. The guard cells regulate the opening and closing in the stoma.

 

 

 

 

 

 

 

 

You should be able to make a drawing of this picture and label with the following: stoma, guard cell, subsidiary cell, chloroplast, nucleus.

 

 

 

 

 

 

 

 

 

TRICHOMES

Pelargonium Leaf

Here you can see some glandular trichomes. They secrete substances which gives geranium its characteristic fragrance.

 

 

 

 

 

 

 

 

 

Here is a close-up of a glandular trichome.

 

 

 

 

 

 

 

 

 

 

As a plant ages the epidermis may be replaced by the periderm, which is included in the dermal tissue system. The dermal tissue system is an artificial category since periderm usually develops from ground tissue (as in the stem). We will examine this tissue closely in the section on stems.
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