" April showers bring May flowers " is a popular saying (at least in England). This months exploration will examine how those flowers manage to do what they do.
Stomata are microscopic pores (holes) found on the underside of leaves and on stems (if there is only one of them it is called a stoma). They occur in the epidermal tissue (the outside skin of the leaf). They can be clearly seen in the center of the dark areas in these scanning electron microscope images. Each pore is bounded by two crescent shaped guard cells. The guard cell wall closest to the pore is thicker than the remaining walls and so is less flexible. It is the guard cells that regulate the opening and closing of the stoma.
The change in the size of the stomata occur in response to a variety of changes in the environment of the leaf; such as light intensity, carbon dioxide concentration and the amount of water in the air.
The stomata are important for the exchange of gases between the outside air and inside of the leaf (for respiration) and also for the evaporation of water.
If we look around at other features on the leaf in the scanning electron microscope, we can see other interesting things. Here are two images taken at different magnifications of a hair on the leaf. If you look carefully you can just see the stomata between the cells on the right of the first image. The shape of the leaf cells is different near to the area where the hair is emerging from the leaf that it is in the previous images.
Can you think of a reason why this should be ?
As well as the leaves, it is ineresting to look at the roots in the microscope. To the unaided eye the roots look smooth and featureless. In the microscope however there are lots of things to see. On the leaf is a large root. It is not smooth but fibrous, like a piece of yarn. On th right is the growing tip of a root. Both of these images show lots of small particles stuck to the surface of the root. Some of these are the bits of dirt that the root was growing in, but many of them could be bacteria and fungus spores, which may interact with the roots and allow them to take up nutrients from the soil, and enable the plant to grow stronger.
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Last Update: 7/16/97