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									                                               AP BIOLOGY PLANT LAB

Use this lab handout and your textbook (Cambell, Chaper 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, pg. 718-719, 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. Each picture/sketch should be clearly titled, the magnification indicated, and should include a
measurement scale. CS = cross-section

PART I-A compare the leaf cross sections (CS) of a privet (C3 dicot) and a Zea/corn ( C4 monocot) (See pgs 196, 725 of
Campbell). 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),
epidermis, stomates, guard cells, bundle-sheath cells, vascular bundle.


 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 text Figure 10-18, page 192.)
    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.

 Figure 5-1 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 the granal and agranal plastids AND indicate the
 cell types in which they are the located.
  Figure 5-2 shows, at higher magnification, portions of granal and agranal plastids in adjacent cells of the
 corn leaf. Identify the plasmdesmata, thylakoids, grana, stroma, and intergrana lamellae of the chloroplast of
 the mesophyll cell.

 PART II-A: 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 CS's gross (general) structure at
 whatever magnification is needed to see the entire stem (Campbell pg. 724). Label vascular bundles, parenchyma
 and, when appropriate, pith, and cortex.

 PART II-B: With higher magnification, look at a vascular bundle of the dicot stem, labeling xylem, phloem,
 sclerenchyma, parenchyma, companion cells, cortex, pith, and cambium..

 PART II-C: Woody stem (Tilia stem 3 year C.S.). Label: vascular cambium, cork cambium, xylem (oldest and
 youngest), phloem (oldest and youngest), growth rings, spring and summer wood. (Campbell 726)

 PART III: Dicot root structure. Label: epidermis, cortex, endodermis, pericyle, xylem, phloem, stele (vascular
 cylinder). (Campbell 722)

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