Quick Lab
GUIDED INQUIRY

Examining Stomata

  1. Obtain different kinds of leaves from your teacher.

  2. Spread a thick coating of clear nail polish on the underside of each leaf.

  3. Wait about 10 minutes for the polish to dry completely.

  4. Attach a strip of clear tape to the polish and gently peel off the tape, lifting the dried polish.

  5. Tape the polish to a clean microscope slide and examine under a 400× lens.

  6. For each leaf, move the microscope stage so you can count stomata from three distinct fields of view.

Palms holding a leaf and coloring it at its tip with a nail paint.

    Analyze and Conclude

  1. Calculate What is the average number of stomata per square cm for each leaf?

  2. Graph Make a graph that compares these averages.

  3. Form a Hypothesis What could account for differences in stoma density among plants? Write a hypothesis.

In general, stomata are open during the daytime, when photosynthesis is active, and closed at night, when open stomata would only lead to water loss. However, stomata may be closed even in bright sunlight under hot, dry conditions in which water conservation is a matter of life and death. Guard cells respond to conditions in the environment, such as wind and temperature, helping to maintain homeostasis within a leaf.

Transpiration and Wilting Osmotic pressure keeps a plant's leaves and stems rigid, or stiff. High transpiration rates can lead to wilting. Wilting results from the loss of water—and therefore pressure—in a plant's cells. Without this internal pressure to support them, the plant's cell walls bend inward, and the plant's leaves and stems wilt. When a leaf wilts, its stomata close. As a result, transpiration slows down significantly. Thus, wilting helps a plant to conserve water.

One rigid and stiff plant and one wilted plant.

FIGURE 23–17 Wilting A plant may wilt when water is scarce.

In Your Notebook Make a list of molecules that are exchanged through the stomata. Which ones primarily enter the leaf? Which ones primarily exit the leaf?

End ofPage 683

Table of Contents

Miller & Levine Biology
About the Authors
Changing the World of Biology Education
Contents
Diversity of Life: A Visual Guide DOL•1–DOL•64
Labs and Activities
Features
UNIT 1 The Nature of Life
1 The Science of Biology
2 The Chemistry of Life
Unit Project
UNIT 2 Ecology
3 The Biosphere
4 Ecosystems and Communities
5 Populations
6 Humans in the Biosphere
Unit Project
UNIT 3 Cells
7 Cell Structure and Function
8 Photosynthesis
9 Cellular Respiration and Fermentation
10 Cell Growth and Division
Unit Project
UNIT 4 Genetics
11 Introduction to Genetics
12 DNA
13 RNA and Protein Synthesis
14 Human Heredity
15 Genetic Engineering
Unit Project
UNIT 5 Evolution
16 Darwin's Theory of Evolution
17 Evolution of Populations
18 Classification
19 History of Life
Unit Project
UNIT 6 From Microorganisms to Plants
20 Viruses and Prokaryotes
21 Protists and Fungi
22 Introduction to Plants
23 Plant Structure and Function
24 Plant Reproduction and Response
Unit Project
UNIT 7 Animals
25 Introduction to Animals
26 Animal Evolution and Diversity
27 Animal Systems I
28 Animal Systems II
29 Animal Behavior
Unit Project
UNIT 8 The Human Body
30 Digestive and Excretory Systems
31 Nervous System
32 Skeletal, Muscular, and Integumentary Systems
33 Circulatory and Respiratory Systems
34 Endocrine and Reproductive Systems
35 Immune System and Disease
Unit Project
A Visual Guide to The Diversity of Life
HOW TO USE THIS GUIDE
THE TREE OF LIFE
Bacteria
Protists
Fungi
Plants
Animals
Appendices
Appendix A Science Skills
Appendix B Lab Skills
Appendix C Technology & Design
Appendix D Math Skills
Appendix E Periodic Table
Glossary
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q, R
S
T
U
V
W
X, Y, Z
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Credits
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