11.2: Procedure

Observations of the Epidermis and Cuticle

1. Obtain a leaf from the Kalanchoe (flaming Katy) plant (or similar succulent).

2. Gently and slowly tear the leaf back in a diagonal direction to separate the epidermis from the rest of the leaf. Your instructor will provide a demonstration of how to do this.

3. Use a pair of forceps to transfer a piece of the epidermis to a microscope slide. Add a drop of water to the specimen and cover with a coverslip.

4. View the slide first at low power (with the 10x objective lens) before increasing the magnification to high power (with the 40x objective lens). Provide a sketch and description of your observations in the space provided. Be sure to label the cells of the epidermis, the cuticle, as well as the stomata and the guard cells.

Observing Differences in Stomatal Density

1. Obtain a leaf sample from the Tradescantia Wandering Jew plant.
2. Place the leaf between your finger and thumb, with the top side of the leaf facing up. Gently, and slowly, tear the leaf back in a diagonal direction with your other hand to separate the upper epidermis from the rest of the leaf (this is known as the epidermal peel technique). Your instructor will provide a demonstration of how to do this.
3. Use a pair of forceps to transfer a piece of the lower epidermis to a microscope slide. Add a drop of water to the specimen and cover with a coverslip.
4. View the slide with the 40x objective lens. Count the number of stomata in your field of view (FOV). Record this information in data table 11.1.
5. Repeat these observations for a total of 3 random, non-overlapping fields . Record this information in data table 11.1.
6. Calculate the mean of the 3 counts. Record this as the mean stomatal density of the upper epidermis in data table 11.1
7. Repeats steps 1-6 with a piece of the lower epidermis. To obtain a sample of the lower epidermis, be sure to hold the leaf with bottom side facing up while performing the epidermal peel. Record this as the mean stomatal density of the lower epidermis in data table 11.1.
8. Obtain a graticule slide with a marked set of gridlines. You will use this to determine the actual size of your FOV.
9. View the slide with the 40x objective lens. Count the number of grid marks that it takes to go from one side of the FOV to the other. Record this information in the space provided as the field of view diameter (FOV_diameter). Note that each grid mark is equivalent to 0.01 mm.
10. Calculate the area of the FOV using the following equation:

    Equation

    𝐴𝑟𝑒𝑎=𝜋×(𝐹𝑂𝑉𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟/2)²

    Note that this is the simply the equation for calculating the area of a circle using the measurement of the radius (r), which is exactly half of the diameter (i.e. 𝐴𝑟𝑒𝑎=𝜋r²).

11. Record this information as the area of the field of view in data table 11.1.
12. Next, calculate the mean stomatal density for both the upper and lower epidermis by dividing the number of stomata by the area of the FOV. Record this information as the mean stomatal density in data table 11.1.

Leaf Venation Patterns

1. Obtain a blade of grass and observe the pattern of veins present using the dissecting microscope. Provide a sketch and a description of your observations in the data table provided. Be sure to include the overall structure and shape of the leaf as well as the pattern of veins present.

2. Obtain a maple leaf and directly observe the pattern of veins present. Provide a sketch and description of your observations in the data table provided. Be sure to include the overall structure and shape of the leaf as well as the pattern of veins present.

Phyllotaxy

1. Obtain 3 stem samples representing each of the three forms of phyllotaxy: opposite (such as basil, maple, dogwood or viburnum), alternate (such as mustard, sunflower, oak or poplar) and whorled (such as whorled milkweed, Joe-Pye weed, burning bush or oleander). Provide a sketch and description of your observations for each specimen in data table 11.2. Be sure to include the arrangements of the leaves observed.

2. You will also be taking measurements of the internode length (distance between nodes) for each of these specimens. To do this, you will measure the distance between one node and the next. Measure internode length (mm) for three successive internodes per stem and calculate mean internode length. Record this as the mean internodal distance in data table 11.2.

Root Apical Meristem

1. Obtain a prepared slide of Allium/onion root tip (root apical meristem). View the slide first at low power (with the 10x objective lens) before increasing the magnification to high power (with the 40x objective lens). Provide a sketch and description of your observations in the space provided. Be sure to label the root cap, zone of cell division, zone of maturation and zone of elongation.

Shoot Apical Meristem

2. Obtain a prepared slide of the Coleus stem tip (shoot apical meristem). View the slide first at low power (with the 10x objective lens) before increasing the magnification to high power (with the 40x objective lens). Provide a sketch and description of your observations in the space provided. Be sure to label the central zone, peripheral zone and rib meristem.