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Comparative Plant Microscopic Anatomy
OBJECTIVES
After completing this exercise, you should be able to do the following:
a. Recognize the following tissue types under the microscope: ground tissue
(parenchyma, collenchyma, sclerenchyma), dermal tissue (epidermis), and
vascular tissue (xylem, phloem, companion cells).
b. Recognize the following cell structures under the microscope: cell wall,
nucleus, leucoplast, cytoplasm, pit, chromoplast, vacuole, tonoplast, sclereids,
chloroplast, guard cells, primary cell wall, secondary cell wall, middle
lamella, cortex and pith.
c. Understand plasmolysis.
d. Freehand sections of plant material to make wet mount slides.
GENERAL INSTRUCTIONS
1. Read through this information carefully.
2. Be sure you understand each item before proceeding to the next step.
3. Check off each step as you do it so that you do not miss a step.
Part 1: HOW TO MAKE A FREEHAND SECTION OF PLANT MATERIAL
1. Hold a wedge of potato (Solanum tuberosum) in one hand and a single-edged
razor in the other hand (See Figure 1). Make a very thin cut at right angles to the
long axis of the wedge. Place your specimen on a clean microscope slide. Add a
drop of distilled water. Add a coverslip as you learned in last week’s lab: Basic
Microscopy in Plant Biology.
Figure 1. How to make a freehand section of plant material
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2. Examine your slide first at scanning power, then low power and finally high
power. Use the figure below as a reference. Draw a picture of the cells you see.
Label cell wall and leucoplasts.
Cell wall
leucoplasts
3. Make a freehand section of a celery (Apium sp.) petiole (that’s the stalk!). Be
sure to include at least one rib in your section. Mount the section in a drop of
distilled water. Examine your section using high power. Use the figure below as
a reference. Draw a picture of the cells you see. Label collenchyma, cell wall,
and cytoplasm.
4.
collenchyma
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Obtain a small piece of pear (Pyrus sp.) fruit (not the skin). Using a dissecting
needle, mash the piece thoroughly on a clean microscope slide. Add a drop of
phloroglucinol-HCl stain and then a coverslip. Phloroglucinol stains lignified cell
walls red. Examine your section using high power. Use figure 9b in your lab text
as a reference. Draw a picture of the cells you see. Label sclerenchyma
sclereids, pit, cell wall, cytoplasm, and parenchyma.
cytoplasm
Cell wall
5. Obtain a small piece of red pepper. Make a freehand section perpendicular to the
skin (so that you obtain skin and flesh). Make a wet mount of your specimen
using distilled water and examine it under high power. Find a cell where you find
the red color. Where is the red in the cell?
6. Draw a picture of your specimen and label cell wall, nucleus, cytoplasm,
vacuole, and chromoplast.
chromoplasts
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7. Obtain a section of apple (Malus sp.). Make a freehand section of the peel by
holding the razor tangentially to the peel. Make a wet mount of your specimen
using distilled water and examine it under high power. Find a cell where you find
the red color. Where is the red in the cell? Is this the same place as the red in the
red pepper?
8. Based on location of the red color, what kind of compound is the red in the apple?
What about in the red pepper?
9. Draw a picture of your specimen and label cell wall, cytoplasm, vacuole, and
tonoplast.
10. Now add 10% NaCl solution to the edge of the coverslip and draw the solution
under the coverslip by placing a paper towel edge next to the opposite side of the
coverslip. Observe the cells through the microscope. Describe what happens to
the vacuole.
Plasmolysis
of cells
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11. Draw a picture of these cells and label cell wall, cytoplasm, vacuole and
tonoplast.
12. Obtain a slide of persimmon (Diospyros sp.) endosperm. Examine the slide under
high power. Use the figure below as a reference. Draw a picture of the cells you
see. Label primary cell wall, secondary cell wall, pit, and middle lamella.
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13. Obtain a slide of Ranunculus sp. (buttercup) stem cross. Examine the slide under
high power. Use the figure below as a reference. Draw a picture of the cells you see.
Label epidermis, cortex, pith, vascular bundle, xylem, phloem, companion cell,
sclerenchyma and parenchyma.
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14. Obtain a slide of Nymphaea sp. (water lily) leaf cross. Examine the slide under high
power. Use figure 9d in your lab text as a reference (your section will be similar but not
identical to this picture. Figure 4.7 in your textbook may help as well). Draw a picture
of the cells you see. Label epidermis, guard cells, chloroplasts, vascular bundle,
xylem, phloem, sclerenchyma fibers and sclereids.
15. Make a wet mount of a single Elodea leaf. Examine the slide under high power. Use
the figure below as a reference. Note the cytoplasmic streaming! Look at the edge of
the leaf. Are the epidermal cells modified in any way? Draw a picture of the cells you
see. Label cell wall, chloroplast and nucleus.