Download link for lab: http://www.sendspace.com/file/f8bx2j
I recommend downloading the lab from that link so you get to see the pictures and the formatting is also better.
Text:
Investigation 7A: Leaf Structure and Stomates (p. 644)
Leaves have structural adaptations that enable them to perform their specific functions efficiently. In this investigation you will examine those structures and try to identify the functions for which they are adapted.
Materials:
Cover slip
Dropping pipet
Iris scissors
Microscope slide
Forceps
Compound microscope
Prepared slide of cross section of a leaf
Several types of fresh leaves
Variety of mature plants from the class
Part A: Leaf Structure and Function
Examine the various plants, the different types of leaves, and the arrangement of leaves on the stems of the classroom plants. Record your observations.
Examine a prepared cross section of a leaf under high power of your microscope. Compare your slide with figure 7.2 to become familiar with the various regions of the leaf. Consider its structure in relation to the functions of light absorption, water supply, and carbon dioxide absorption.
Locate chloroplasts in the leaf cells. Note their shape and abundance in the various leaf cells.
Locate a cross section of a small vein in the center tissues of the leaf. The vein is surrounded by a sheath (covering) of cells that also are photosynthetic. Notice some of the empty cells with thick walls in the upper part of the sectional leaf.
Examine the covering layers of the leaf – the upper epidermis and the lower epidermis. These single layers of cells are covered by the cuticle, which may have been removed when the slide was made.
Locate a stomate and its guard cells. Locate the spongy tissue just below the lower epidermis. Note how the stomates are located in relation to the spongy tissue.
Analysis:
What might be the advantage of a flat, thin leaf blade to the photosynthetic capacity of the plant?
How does the arrangement of leaves on a stem relate to the photosynthetic capacity of the plant?
On the basis of your observations of chloroplast locations in the leaf, which cells are the main photosynthetic cells?
How might the location of chloroplasts in these cells be advantageous to the plant?
Suggest a function for the thick-walled, empty cells in a leaf vein.
Explain how the cuticle may affect the efficiency of photosynthesis.
Compare the structure of the spongy tissue to that of the other leaf tissues.
Explain how the location of stomates in spongy tissue is related to the function of the spongy layer.
Write a short paragraph summarizing how the leaf structures you observed are adapted for leaf functions.
Part B: Number of Stomates
While holding the lower surface of a leaf upward, tear the leaf at an angle. The tearing action should peel off a portion of the lower epidermis. It will appear as a narrow, colorless zone extending beyond the green part of the leaf.
Lay the epidermis in a drop of water on a slide and use the scissors to cut of a small piece. Add a cover slip. Do not allow the epidermis to dry out. Caution: Scissors are sharp; handle with care.
Using the low-power objective of your microscope, locate some stomates. Then switch to the high-power objective. Make a sketch to show the shape of a stomata, its guard cells, and a few adjacent cells in the epidermis.
Count the number of stomates in the high-power field for 10 different areas of the epidermis. Record your observations.
In the same manner, count the stomates on the upper epidermis of the same leaf. Examine as many other types of leaves as possible. Compare the number of stomates per mm2 on the upper and lower surfaces of each type of leaf.
Wash your hands thoroughly before leaving the laboratory.
Analysis:
Calculate the average number of stomates per mm2 of the leaf’s surface. (Area of a circle. You need the diameter of your field of you to calculate the diameter)
How did the number of stomates per mm2 in different areas of the same side of a piece of leaf epidermis compare? On the opposite side?
Did the stomates vary in the amount they were open? How can you explain your findings?
What would you do to assure a reliable comparison of the number of stomates per mm2 for two species of plants?
What do your data suggest about the distribution of stomates in leaves of your species of plant? What assumption must you make in drawing this conclusion?
- Here are the concepts to study for the test.
- Invention of microscope
- Unicellular vs. Multicellular
- Organelles - structure and function
- Active and Passive Transport
- Plant vs. Animal Cells
- Molecular polarity and size
- * 1 short answer question will be on cell membrane *
Well I have never done this so I dunno how this is gonna turn out... but you can see the four whiteboards that Mrs. Cebulski put up. The second picture, which is just a corner of the whiteboard, is the corner that is missing from the third picture's whiteboard. I'm pretty sure you can enlarge it by clicking on it, but I can't try from this edit box.
Here are the tables you can put your info in courtesy of Elbek. The invertebrates table needs a few extra columns.
Download it:
Vertebrates: http://www.sendspace.com/file/jn3vgd
Invertebrates: http://www.sendspace.com/file/rb8f59
