# ______ Name _________________________
Mrs. G-M (300 Biology)
Introduction
Date _________
Period ________
Leaf Structure Lab
A leaf is one of the organs of a plant. The main function of a leaf is to carry out photosynthesis. Photosynthesis is
carried out in the cells by organelles called chloroplasts with the aid of chlorophyll (a green pigment that absorbs light
to provide energy for photosynthesis). The food produced (glucose) is carried to other plants parts through transport
tubes called phloem. Since leaves are organs, they are made of many different kinds of tissues. These tissues appear as
layers of cells. Each tissue has a specific function and the shape of the cells in the tissue is related to its function.
Some cells look like small boxes stacked side by side, while others are long and balloon-shaped. Certain cells are round
and loosely packed, while others look like small tubes stacked together.
Objective
To observe and identify the different tissues within a leaf and determine their functions.
Materials






prepared slide of a cross-section of a leaf
prepared slide of the epidermis of a dicot leaf (or a wet mount of the lower epidermis of a green onion/leek)
microscope
diagram of a leaf
colored pencils
tape
Procedure
Part I-Making a Model of a Leaf
1. Color the parts of "Figure 1. Tissue Layers of a Leaf" (at the end of this lab) using the key below:
a. upper & lower cuticle (waxy layer)- yellow
b. upper epidermis- orange
c. lower epidermis- pink
d. spongy (mesophyll) layer- light green
e. palisade (mesophyll) layer- dark green
f. xylem (part of vascular bundle)- red
g. phloem (part of vascular bundle)- blue
h. guard cells- purple
2. Cut out the layers.
3. Assemble the model of the leaf on the back of this page given (using tape not glue).
a. Start with the upper epidermis and work your way down.
b. HINT: The xylem and phloem fit together like a puzzle.
4. Label the different parts of the leaf using the key given above.
# ______ Name _________________________
Mrs. G-M (300 Biology)
Leaf Tissue Cross-Section Model
Date _________
Period ________
Construct your leaf model here. Don't forget to color and label (or make a key) for your model!
# ______ Name _________________________
Mrs. G-M (300 Biology)
Date _________
Period ________
Part I I- Examining the Tissues of a Leaf (cross-section)
1. Examine a prepared slide of a leaf cross-section under LOW power.
2. Locate and identify the 6 cell layers in the leaf section (both waxy cuticle layers, the upper and lower epidermis,
the spongy mesophyll layer, and the palisade mesophyll layer).
3. Also locate and identify air spaces, veins/vascular bundles, stomata (if visible), and guard cells (if visible).
4. Draw a portion of the leaf cross-section on LOW power below. Try to make sure you pick a portion of the leaf in
which all of the parts you located and identified are present. Make your drawing large and NEAT enough to be
able to see the details and differentiate the parts.
5.
Label the following parts:
a.
b.
c.
d.
e.
f.
g.
h.
i.
both waxy cuticle layers
the upper epidermis
lower epidermis
spongy mesophyll layer
palisade mesophyll layer
air spaces
veins/vascular bundles
stomata (if visible)
guard cells (if visible)
# ______ Name _________________________
Mrs. G-M (300 Biology)
Date _________
Period ________
Part III - Observing Stomata in the Lower Epidermis of a Dicot Leaf
1. Examine a prepared slide of the lower epidermis of a dicot leaf under low power. (You may prepare a wet mount
of the lower epidermis of a green onion/leek instead. If so, separate directions will be given to you.)
2. Locate the epidermal cells (which appear like long diamond-shaped cells and will be the most common cells in your
field of view).
3. Switch to medium power and refocus.
4. Then, switch to HIGH power and refocus.
5. Locate and identify the:
a. epidermal cells (long-diamond shaped cells)
b. guard cells (paired sausage-shaped cells)
c. stomata (opening between paired guard cells)
d. chloroplasts (green dots within guard cells)
6. Draw a portion of the lower epidermis of the dicot leaf on HIGH power below. Make your drawing large and
NEAT enough to be able to see the details and differentiate the parts.
7.
Label the following parts:
a.
b.
c.
d.
epidermal cell
guard cells
stomata
chloroplast
# ______ Name _________________________
Mrs. G-M (300 Biology)
Date _________
Period ________
Questions:
1. What is the major function of leaves? ___________________________________________________________
2. List the functions of the following leaf parts:
a. cuticle- _____________________________________________________________________________
___________________________________________________________________________________
b. upper and lower epidermis-______________________________________________________________
___________________________________________________________________________________
c. guard cell- __________________________________________________________________________
___________________________________________________________________________________
d. spongy mesophyll layer- ________________________________________________________________
___________________________________________________________________________________
e. palisade layer- ________________________________________________________________________
___________________________________________________________________________________
f. xylem- _____________________________________________________________________________
___________________________________________________________________________________
g. phloem- ____________________________________________________________________________
___________________________________________________________________________________
h. stomata- ____________________________________________________________________________
___________________________________________________________________________________
3.
How many cell layers thick is the upper and lower epidermis? _________ Why? __________________________
________________________________________________________________________________________
# ______ Name _________________________
Mrs. G-M (300 Biology)
Date _________
Period ________
4. How is the cuticle similar to a plastic bag? ________________________________________________________
_________________________________________________________________________________________
5. Describe the differences in shapes of the cells in the palisade layer and the spongy layer? ____________________
_________________________________________________________________________________________
Why do you think each is shaped that way? _______________________________________________________
_________________________________________________________________________________________
6. What happens to the size of the stomata if the guard cells are closer together? ____________________________
How does this affect the gases and that enter and exit the leaf (as well as the water that exits)? ________________
_________________________________________________________________________________________
7. Would you expect a desert plant to have:
a. many stomata or few stomata? _____________________ Why? ________________________________
___________________________________________________________________________________
b. Would you expect a desert plant to have a thin cuticle or a thick cuticle? Why? ______________________
___________________________________________________________________________________
8. A water lily floats in water. In which layer, the upper epidermis or lower epidermis, would you expect to find
stomata? ___________________________________________ Why? _________________________________
_________________________________________________________________________________________
9. The celery stalks that you eat are leaf stalks. What kinds of cells are the “strings” inside the celery? ____________
_________________________________________________________________________________________
# ______ Name _________________________
Mrs. G-M (300 Biology)
Date _________
Period ________