CHAPTER 39 PLANT RESPONSES TO INTERNAL AND EXTERNAL SIGNALS Learning objectives Read pages 821-849 of “Biology” Campbell 9th edition to make your Cornell notes and understand the following learning objectives below. Supplementary reading can be from the photocopied supplements from “Biology Study Guide” Campbell & Reece and Cliff Notes AP Biology. Remember the following are NOT questions but guidelines for your note taking. Reading for comprehension and identifying key ideas and concepts is a skill required for AP Biology. NO COPIED NOTES ALLOWED! Signal Transduction and Plant Responses Compare the growth of a plant in darkness (etiolation) to the characteristics of greening (de-etiolation). Describe the signal pathways associated with de-etiolation. Describe the two main mechanisms by which a signaling pathway can activate an enzyme. Plant Responses to Hormones Why is the term “plant growth regulator” used to describe plant hormones? List six classes of plant hormones, describe their major functions, and note where they are produced in the plant. Plant Responses to Light Define circadian rhythm and explain what happens when an organism is artificially maintained in a constant environment. Define photoperiodism. Distinguish between short-day, long-day, and day-neutral plants. Explain why these names are misleading. Plant Responses to Other Environmental Stimuli Describe how plants apparently tell up from down. Explain why roots display positive gravitropism and shoots exhibit negative gravitropism. Distinguish between thigmotropism and thigmomorphogenesis. Provide a plausible explanation for how a stimulus causing rapid leaf movement can be transmitted through the plant. Plant Defenses against Herbivores and Pathogens Explain how plants deter herbivores with physical and chemical defenses. Describe how plants may recruit parasitoids to attack herbivorous caterpillars. Describe how the hypersensitive response helps a plant limit the damage from pathogen attack. 1