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Basic Scientific Experiments that Students Can Perform: Exploring a Leaf under the Microscope

For our microscope activity, we will be examining the leaf of a plant under the microscope. This microscope activity is very helpful to high school and elementary students who are studying about plants or biology. We will be also using a low power stereo microscope and a high power compound microscope. If only a cheap child microscope or kid microscope is available, it can also be used by children.

Leaves are called the factories of the botanical plant. Raw materials like water and carbon dioxide that are absorbed by the different parts of the plant are converted by the leaves into sugar and starch. This process is called “photosynthesis” wherein the leaf’s machines called chloroplasts uses the sun’s light in order to manufacture these raw materials into food.

Our science microscope activity involves exploring this little factory under the microscope. First, let’s have a brief overview of the parts of a leaf. A leaf consists generally of a stalk called petiole and a blade that is broadly thin. If we look at this blade using a magnifying lens (known as a simple microscope), we will see numerous veins that run in all directions. This is where the water passes from the roots. Food is also manufactured in this area.

Let us also look at the leaf under a low power stereo microscope, known as the stereoscope. You will see that there are green round bodies that are scattered throughout the surface of the leaf. These are the chloroplasts that are, as mentioned above, responsible for the food production and the overall color of the leaf.

Let us then move on with examining the structure of a leaf using a high power compound microscope. Take a very tiny specimen of the leaf and place on a blank microscope slide, then cap it with a cover slip. You may need a tiny drop of water under the cover slip. Turn the objective to the lowest power first, then gradually to higher powers of magnification using the other objectives. Use the focusing knob as needed. Note that as your power of magnification increases, the microscope field of view decreases and it is necessary to do more fine focusing. We will see that a leaf has layers of cells. The outermost layer is called the epidermis where microscopic hairs grow to cover and protect the leaf. If we peel off some of this epidermis and examine it under a compound light microscope, we will see that it has irregular spaces like tiles of a puzzle. These are the cells and the lines that outline each space are called the cell walls.

If you look at these cells closely under a high power kid microscope, you will notice that there are bodies that are shaped like crescent or kidneys. The ends of these crescent-shaped bodies touch to form an elliptical opening called the stomata (which is derived from the Greek word that means mouth). The stomata are responsible for allowing air to enter the tissues of the leaf. It is also where the vapour, excess water or unnecessary materials for the production of food are released. These crescent-shaped bodies are known as the guard cells. They expand when there is presence of water and contract when there is already too much of it.

After the epidermis, we will examine under a high power compound light microscope the internal parts of the leaf. In order to perform this, we will need a cross section of the leaf. What students or children will do is to roll a leaf blade. Use a razor (teachers should remind their students to be careful when handling sharp objects) to slice through the roll as thinly as possible. It is ideal that the slice is so thin that it will appear almost transparent. Mount a small bit of this section on a microscope slide with a drop of water. Place it on the microscope stage of a high power compound light microscope.

The structure of the leaf’s anatomy under a high power microscope is like a very thin sandwich. You will first notice the upper and lower epidermis which looks like flattened cells. Between these microscopic cells are numerous chloroplasts that are collectively called the leaf’s mesophyll. This is where the manufacture of the food takes place in this botanical specimen.

You will also notice elongated cells that are close to each other. These are known as palisade cells and below these cells is a spongy region of mesophyll that is separated by air spaces. These air spaces are somehow connected to one another and to the stomata. The leaf’s veins are also located in the mesophyll.

Examining the makings of a leaf can prove to be very educational to students or children especially to those who are curious as to how the leaf manufactures its own food. Furthermore, students will also be more adept in using their low power and high power microscopes as this gives a helpful lesson in their use.

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