Ch 39: Campbell Biology Chapter 39: Plant Responses to Internal and External Signals
About This Chapter
How It Works:
- Identify the lessons in the Campbell Biology Plant Responses to Internal and External Signals chapter with which you need help.
- Find the corresponding video lessons with this companion course chapter.
- Watch fun videos that cover the plant responses topics you need to learn or review.
- Complete the quizzes to test your understanding.
- If you need additional help, rewatch the videos until you've mastered the material or submit a question for one of our instructors.
Students will learn:
- What signal transduction is
- Kinds of plant hormones and their functions
- Types of plant photoreceptors
- The definition for phototropism
- Categories of photoperiodic plants
- Types of tropisms
- Different stimuli that plants respond to
- Kinds of plant defenses
Campbell Biology is a registered trademark of Pearson Education, which is not affiliated with Study.com.

1. Signal Transduction in Plants: From Reception to Response
Changes in cellular activity induced by external signals are called signal transductions. Discover the signal pathways from reception to response and the popular plant signal transduction.

2. Plant Hormones: Chemical Control of Growth and Reproduction
Like in humans, plants have hormones that are chemical receptors that control growth and reproduction. Learn about the function of hormones and the four different types of hormones found in plants.

3. Gibberellins in Plants: Definition & Function
Gibberellins are plant hormones that promote and regulate growth. Learn how to define gibberellins, explore their function, and discover their uses in farming and florist's shops.

4. Abscisic Acid in Plants: Definition & Function
Abscisic acid (ABA) is a plant hormone that regulates numerous aspects of plant growth, development, and stress responses. Study the definition and function of abscisic acid in this lesson.

5. Plant Photoreceptors: Definition, Types & Function
The photoreceptors of plants perceive light and regulate biological activities within plants. Learn more about the definition of plant photoreceptors, the two different types of photoreceptors, and their specific functions.

6. What Is Phototropism? - Definition, Experiments & Examples
Phototropism refers to plant growth in the direction of a light source. Explore the definition of phototropism, results of early experiments, and examples of the two types: negative and positive phototropism.

7. Photoperiodicity: Short-day, Long-day and Day-Neutral Plants
Photoperiodism is an organism's response to the length of the day vs the length of the night. The length of daylight can affect the growth of a plant. Discover how plants are classified into short-day, long-day, and day-neutral plants based upon their exposure to daylight in this lesson.

8. Tropisms: Phototropic, Geotropic and Thigmotropic Plant Growth
Explore the key types of tropisms that allow plants to respond to their environment. Learn to define tropism and explore phototropic, geotropic, and thigmotropic plant growth.

9. How Plants Respond to Gravity
Plants respond to gravity by growing towards or away from the earth, partially influenced by biochemical signals. Learn about plant stimuli, gravitropism (or geotropism), and statoliths.

10. Plant Responses to Mechanical Stimuli
Although less noticeable than most animals, plants respond to mechanical stimuli as well. Learn three types of responses of plants to mechanical stimuli: thigmomorphogenesis, thigmotropism, and thigmonasty.

11. Environmental Stimuli & Stress: Plant Adaptations & Responses
Discover the variety of abiotic stresses, also known as environmental stresses, that can affect plants, such as floods, droughts, heat, and cold. Finally, learn how plants combat these stresses, including using heat-shock proteins.

12. How Plants Defend Against Pathogens & Herbivores
Plants have defense mechanisms that activate when they are threatened by herbivores or infected by pathogens. Learn about different attacks on plants, their defense mechanisms against herbivores, and their defense mechanisms against pathogens.
Earning College Credit
Did you know… We have over 220 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.
To learn more, visit our Earning Credit Page
Other Chapters
Other chapters within the Campbell Biology: Online Textbook Help course
- Campbell Biology Chapter 1: The Themes of Biology, and Scientific Inquiry
- Campbell Biology Chapter 2: The Chemical Context of Life
- Campbell Biology Chapter 3: Water and Life
- Campbell Biology Chapter 4: Carbon and the Molecular Diversity of Life
- Campbell Biology Chapter 5: The Structure and Function of Large Biological Molecules
- Campbell Biology Chapter 6: A Tour of the Cell
- Campbell Biology Chapter 7: Membrane Structure and Function
- Campbell Biology Chapter 8: An Introduction to Metabolism
- Campbell Biology Chapter 9: Cellular Respiration and Fermentation
- Campbell Biology Chapter 10: Photosynthesis
- Campbell Biology Chapter 11: Cell Communication
- Campbell Biology Chapter 12: The Cell Cycle
- Campbell Biology Chapter 13: Meiosis and Sexual Life Cycles
- Campbell Biology Chapter 14: Mendel and the Gene Idea
- Campbell Biology Chapter 15: The Chromosomal Basis of Inheritance
- Campbell Biology Chapter 16: The Molecular Basis of Inheritance
- Campbell Biology Chapter 17: Gene Expression: From Gene to Protein
- Campbell Biology Chapter 18: Regulation of Gene Expression
- Campbell Biology Chapter 19: Viruses
- Campbell Biology Chapter 20: DNA Tools and Biotechnology
- Campbell Biology Chapter 21: Genomes and Their Evolution
- Campbell Biology Chapter 22: Descent With Modification: A Darwinian View of Life
- Campbell Biology Chapter 23: The Evolution of Populations
- Campbell Biology Chapter 24: The Origin of Species
- Campbell Biology Chapter 25: The History of Life on Earth
- Campbell Biology Chapter 26: Phylogeny and the Tree of Life
- Campbell Biology Chapter 27: Bacteria and Archaea
- Campbell Biology Chapter 28: Protists
- Campbell Biology Chapter 29: Plant Diversity I
- Campbell Biology Chapter 30: Plant Diversity II
- Campbell Biology Chapter 31: Fungi
- Campbell Biology Chapter 32: An Overview of Animal Diversity
- Campbell Biology Chapter 33: An Introduction to Invertebrates
- Campbell Biology Chapter 34: The Origin of Evolution of Vertebrates
- Campbell Biology Chapter 35: Plant Structure, Growth, and Development
- Campbell Biology Chapter 36: Resource Acquisition and Transport in Vascular Plants
- Campbell Biology Chapter 37: Soil and Plant Nutrition
- Campbell Biology Chapter 38: Angiosperm Reproduction and Biotechnology
- Campbell Biology Chapter 40: Basic Principles of Animal Form and Function
- Campbell Biology Chapter 41: Animal Nutrition
- Campbell Biology Chapter 42: Circulation and Gas Exchange
- Campbell Biology Chapter 43: The Immune System
- Campbell Biology Chapter 44: Osmoregulation and Excretion
- Campbell Biology Chapter 45: Hormones and the Endocrine System
- Campbell Biology Chapter 46: Animal Reproduction
- Campbell Biology Chapter 47: Animal Development
- Campbell Biology Chapter 48: Neurons, Synapses, and Signaling
- Campbell Biology Chapter 49: Nervous Systems
- Campbell Biology Chapter 50: Sensory and Motor Mechanisms
- Campbell Biology Chapter 51: Animal Behavior
- Campbell Biology Chapter 52: An Introduction to the Ecology of the Biosphere
- Campbell Biology Chapter 53: Population Ecology
- Campbell Biology Chapter 54: Community Ecology
- Campbell Biology Chapter 55: Ecosystems and Restoration Ecology
- Campbell Biology Chapter 56: Conservation Biology and Global Change