Introduction: In this lab you observe "typical", undifferentiated, plant cells (parenchyma). You should have note the characteristics that plant cells share with all other eukaryotic cells (the nucleus and membrane-bound organelles) and also note the characters where plant cells differ from animal cells (large central vacuole, plastids, and cell wall).
Go to our directory of images for the Plant Cell.
The Elodea Leaf Cell:
These cells were vitally stained with Janus Green - students should recognize chloroplasts, nuclei, and the large central vacuole in each cell. Determining the extent of the vacuole requires through focusing.
Tradescantia Stamen Hair Cell:
These flowers have hairs associated with their stamens which consist of filaments of cells. These cells are ideal for studying the plant cell because they are not embedded in a tissue and because they lack chloroplasts. Students should clearly discern, the cell wall, cytoplasm, the nucleus, the location of the vacuolar membrane (the tonoplast), cytoplasmic threads transversing the vacuole, and also observe the phenomenon of cytoplasmic streaming.
Plastids:
Chromoplasts:
Plastids in fruits: Chloroplasts in green fruit become chromoplasts in the ripe fruit
Leucoplasts: leucoplasts can be easily seen in the cells along the intact margin of a Zebrina leaf.
Chloroplasts: Chloroplasts can be easily seen in any green plant tissue. Typically plant cells have disk-shaped chloroplasts as seen in this linked view of a moss protonema.
Starch Grains: Starch is always associated with plastids in all plant cells. This is true even when the starch grain becomes so massive that no other aspect of the plastid is visible with the light microscope. Starch grains are easily seen in potato tissue.
The Cell Wall: In tissues, the primary plant cell wall is perforated with cytoplasmic tunnels that connect the protoplasts of adjascent cells. These channels are barely resolvable with the light microscope. In lab students view tissue from the endosperm of Diospyros (Persimmon). In this tissue, nutrients are stored in the form of hemicellulose in the primary walls. Because these walls are so thick the plasmodesmata are extremely long and this renders them visible to the light microscope. The boundary between adjacent cells (the middle lamella) is also clearly visible in the tissue.
Crystals: Another aspect of plant cells is that they often form crystals of calcium oxylate inside their vacuoles. These can take on a variety of different forms. Two were seen in lab.
a. Raphides: These are needle-shaped.
Link to view of raphides in Sansievieria leaf tissue
b. druses: These are spherical with a jagged margin
Link to view of druses in Begonia petiole tissue
The Plant Cell as Seen with the Transmission Electron Microscope
Electron micrographs courtesy of Dr. Eldon Newcomb:
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1. Young Plant Cell: view of nucleus, mitochondria and vacuoles
2. Plant Cell: view of nucleus with nucleolus, mitochondria chloroplasts and vacuole
3. Plant Cell: View of nuclear envelope, microbodies, mitochondria, and a chloroplast
4. Plant Cell: view of a chloroplast showing detail of the grana
7. Plant Cell: View of leucoplast with mitochondrion and endoplasmic reticulum
8. Plant Cell: View of microtubules below the cell wall (glancing section)
9. Plant Cell: View of microtubules below the cell wall (cross section of microtubules)
10. Plant Cell: View of plasmodesmata (longitudinal secton)
11. Cell Wall: View of plasmodesmata (cross section)
12. Plant Cell: view of parenchyma cell with a large central vacuole
13. Plant Cell: Endoplasmic reticulum with polysomes