Name
Period
LEAF STRUCTURE AND PLANT TISSUE LAB
Objectives: Use this lab handout and your textbook (Campbell, Chapter 35) to familiarize yourself with the different cell and
tissue types found in plant leaves, stems, and roots. You are responsible for identifying these structures from
drawings, pictures, or electron photomicrographs and for knowing their function(s). You will learn much more if the reading precedes the lab!!! Be sure to bring your text to class each day, and let it
assist you with the lab. In particular, check out the basic tissue types in Campbell 7th edition, pg. 718-719 or,
Campbell 10th edition, pg. 758-759, before you go any further! As you observe the microscope slides in class, find
the structures indicated in this handout and then label the sketches with a #2 pencil and color if necessary.
Each picture/sketch should be drawn to correct proportion, clearly titled, and the total magnification given.
Materials: 1 prepared slide of monocot and dicot leaf cross-section. A small piece of fresh lettuce and a small piece of
wilted lettuce, 1 slide and cover slip. The textbook is always helpful. Procedure: PART I: The LEAVES
A) Compare the leaf cross sections (Figure 1) of a privet (C3 dicot) and (Figure 2) a Zea/corn ( C4 monocot)
(Campbell 7th edition, pg. 196, 725 or Campbell 10th edition, pg. 202-765). Use the handout and the included electron
photomicrographs to compare the structure of these leaves to one another, and to their form of carbon fixation
(C3 vs C4). Label: cuticle, mesophyll (distinguish palisade and spongy in C3), epidermal layer, stomata, guard
cells, bundle-sheath cells, vascular bundle (indicate xylem & phloem).
*Also, label the path that carbon dioxide would take to get into the mesophyll cells (from the air through
stomata, through the intercellular space of the spongy mesophyll, to the palisade mesophyll).
C3 VERSUS C4 PHOTOSYNTHESIS:
Two main groups of higher plants can be distinguished on the basis of their initial photosynthetic products,
the C3 plants and the C4 plants. The initial photosynthetic products in the C3 plants are C3 phosphorylated
compounds, whereas in C4 plants they are C4 dicarboxylic acids.
In C3 plants, chloroplasts of similar appearance are distributed throughout the leaf, and the Calvin cycle
takes place in each mesophyll cell, beginning with the fixation of atmospheric CO2 by carboxylation of
ribulose diphosphate (RuBP) to form 3-phosphoglycerate (PGA). (See Cambell 7th edition Figure 10-18,
page 192. or See Cambell 10th edition Figure 10-19, page 200.)
In C4 plants, the biochemical events of photosynthesis are compartmentalized. Mesophyll cells containing
plastids with well-developed grana (granal plastids) fix atmospheric CO2 by the phosphoenol pyruvate
(PEP) system. This results in the formation of oxaloacetic acid, a four-carbon compound, which is rapidly
converted into a different four carbon acid (malic or aspartic acid). This four-carbon acid is then
transported into adjacent bundle-sheath cells that contain agranal plastids (i.e. plastids which often have
poorly developed grana or lack grana entirely). Within these agranal plastids of the bundle-sheath cells,
CO2 is released from malic or apartic acid and then fixed to the RuBP via the normal Calvin cycle pathway.
B) Figure 3: is an electron micrograph showing portions of bundle-sheath cells and adjacent mesophyll
cells from a leaf of the corn (Zea mays) plant, a C4 plant. Label: granal and agranal plastids AND
indicate the cell types in which they are the located.
C) Figure 4: shows, at higher magnification, portions of granal and agranal plastids in adjacent cells of the
corn leaf. Label: plasmodesmata, thylakoids, grana, stroma, and intergranal lamellae of the
chloroplast in the mesophyll cell.
1 D) Lettuce Cells and Stomates:
1. Prepare two wet mount slides one of crisp lettuce and one of wilted lettuce. You can scrape the lettuce with your
fingernail or scalpel to peel off a very thin layer of cuticle for viewing.
2. Use the microscopes to look at the stomata of the wilted lettuce and the crisp lettuce. Using the field o’view
circles, sketch the stomata of each piece of lettuce, noting the differences between the two. It is important that
your drawings are proportional to the field of view. Label: stomatal pore and guard cells.
Crisp Lettuce X Wilted Lettuce X a) What is the relationship between stomata and guard cells?
b) Make a list of the things that cause stomata to open and close.
c) Explain what the differences were in these two epidermal slides.
d) Describe any of the unique techniques employed by plants to minimize water loss.
PART II: The STEMS
A) Figure 5: Review the structure of a dicot stem, in particular with regards to arrangement of the vascular
bundles. Using the “annual dicot” (Ranunculus) stem C.S., view each of the (general) structures at whatever
magnification is needed to see the entire stem (Campbell 7th edition pg. 724 or Campbell 10th edition pg. 764).
Label: epidermis, vascular bundles, parenchyma, pith and cortex.
B) Figure 6: With higher magnification, look at a vascular bundle of the dicot stem. Label: epidermis,
xylem, phloem, sclerenchyma, parenchyma, companion cells, pith and cortex.
C) Figure 7: Woody stem (Tilia stem 3 year C.S.). Label: bark, vascular cambium, cork cambium,
xylem (oldest and youngest), phloem (oldest and youngest), growth rings, spring and summer wood.
(Campbell 7th edition pg. 726 or Campbell 10th edition pg. 766)
PART III: The ROOTS
A) Figure 8: Dicot root structure. Label: epidermis, cortex, endodermis, xylem, phloem, stele
(vascular cylinder). (Campbell 7th edition pg. 722 or Campbell 10th edition pg. 762)
2 FIGURE 1 FIGURE 2 3 LEAF ELECTRONMICROGRAPHS:
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Figure 3. Electron micrograph of portions of mesophyll cells with granal plastids
(bottom) and contiguous bundle-sheath cells with agranal plastids (top) in a corn
(Zea mays) leaf, x 8,300. Before this plant was fixed and prepared for electron
microscopy, it was kept in the dark for 24 hours. Focus on the sheath cells and note
the lack of starch grains in their agranal plastids. Also locate the numerous plasmodesmata that occur in the walls between the sheath cells, and in the walls between
the sheath cells and the mesophyll cells.
4 Figure 4. Electron micrograph of a portion of a granal plastid in a mesophyll
cell (right) and a portion of an agranal plastid in a bundle-sheath cell (left) of a corn
(Zea mays) leaf, X 59,500. Note the plasmodesmata in the wall between these two
cells.
5 Figure 5 Figure 6
6 Figure 7 7 Figure 8
8