LEAF STRUCTURE AND PLANT TISSUE LAB

Size: px

Start display at page:

Download "LEAF STRUCTURE AND PLANT TISSUE LAB"

Anastasia Angelica Washington
5 years ago
Views:

1 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 7 th edition, pg or, Campbell 10 th edition, pg , 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: Compound microscope, prepared slides of monocot and eudicot leaf cross-section, monocot and eudicot stems, and woody stem Basswood. 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: View a double mount prepared slide of monocot and eudicot leaf cross-section. A) Compare the leaf cross sections (Figure 1) of a Privet (C 3 eudicot) and (Figure 2) a Zea mays/corn ( C 4 monocot) (Campbell 7 th edition, pg. 196, 725, or Campbell 10 th edition, pg ). 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 (C 3 vs C 4 ). Label: cuticle, mesophyll (distinguish palisade and spongy in C 3 ), epidermal layer, stomata, guard cells, bundle-sheath cells, vascular bundle (indicate xylem & phloem). *Also, in both the C 3 and C 4 leaves, 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, don t forget the bundle sheath cells in the C 4 leaf, Figure 2). C 3 VERSUS C 4 PHOTOSYNTHESIS: Two main groups of higher plants can be distinguished on the basis of their initial photosynthetic products, the C 3 plants and the C 4 plants. The initial photosynthetic products in the C 3 plants are C 3 phosphorylated compounds, whereas in C 4 plants they are C 4 dicarboxylic acids. In C 3 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 CO 2 by carboxylation of ribulose diphosphate (RuBP) to form 3-phosphoglycerate (PGA). (See Cambell 7 th edition Figure 10-18, page 192. or See Cambell 10 th edition Figure 10-19, page 200.) In C 4 plants, the biochemical events of photosynthesis are compartmentalized. Mesophyll cells containing plastids with well-developed grana (granal plastids) fix atmospheric CO 2 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, CO 2 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 C 4 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

2 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: View a double mount prepared slide of monocot and eudicot stem cross-section, and a triple mount woody stem Basswood. A) Figure 5: Review the structure of a eudicot stem, in particular with regards to arrangement of the vascular bundles. Using the eudicot (Sunflower) stem C.S., view each of the (general) structures at whatever magnification is needed to see the entire stem (Campbell 7 th edition pg. 724, or Campbell 10 th 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 (tracheid/vessel element), phloem, sclerenchyma, parenchyma, companion cells, pith & cortex. C) Figure 7: Review the structure of a monocot (Zea/corn) stem, in particular with regards to arrangement of the vascular bundles as compared to the eudicot stem (Campbell 7 th edition pg. 724, or Campbell 10 th edition pg. 764). Label: epidermis, vascular bundles, and ground tissue. D) Figure 8: Woody stem, (Talia, Basswood stem 3 year C.S.). (Campbell 7 th edition pg. 726, or Campbell 10 th edition pg. 766). Label: bark, vascular cambium, cork cambium, xylem (oldest and youngest), phloem (oldest and youngest), growth rings, spring and summer wood. PART III: The ROOTS A) Figure 9: Eudicot (Sunflower) root structure. (Campbell 7 th edition pg. 722, or Campbell 10 th edition pg. 762). Label: epidermis, cortex, endodermis, xylem, phloem, stele (vascular cylinder). 2

3 FIGURE 1: Privet (C3 eudicot) FIGURE 2: Zea mays/corn ( C4 monocot) 3

$LEAF ELECTRON MICROGRAPH: ) \.........,. -......,..........". '.... :.. :....,. '. :............ '.,, I Figure 3.$

4 LEAF ELECTRON MICROGRAPH: ) \ , , ". '.... :.. :....,. '. : '.,, I 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 plasmo- desmata that occur in the walls between the sheath cells, and in the walls between the sheath cells and the mesophyll cells. 4

5 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

6 Figure 5: Eudicot (Sunflower) Stem, (C3 eudicot) Figure 6: Eudicot (Sunflower) Stem (C3 eudicot) - higher magnification 6

7 Figure 7: Zea mays/corn Stem (C4 monocot) 7

8 Figure 8: Woody stem. (Talia, Basswood 3 years growth) 8

9 Figure 9: Eudicot root structure 9

Name: Plant stems and leaves (p. 1 of )

Name: Plant stems and leaves (p. 1 of ) Introduction: Plants have a variety of configurations but the same basic structures. The three main parts of a plant are the roots, stems, and leaves. The tracheids