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Killing Chloroplasts

Herbicides Targeting Photosynthesis


Angela K. Hartsock
Department of Biology
University of Akron, Wayne College


This case study takes place at a fictional biotechnology company developing herbicides against invasive plant species. The case study focuses on five herbicides with different effects on photosynthesis. Students play the role of lab interns and explore photosynthesis and the herbicide effects by engaging in concept mapping, experimental design, data manipulation, and data analysis. The goal is to use the experimental data to predict the steps in photosynthesis that are inhibited by each herbicide. Students should come away from the case study with a process-based understanding of photosynthesis. This case study is designed for the "flipped" classroom with suggested preparatory videos and associated assessment questions included. Videos can be supplemented with textbook readings or mini-lectures. This activity was developed for a non-majors introductory biology course but it could also be used in any general biology course, including majors' courses. It might also be used to establish foundational knowledge for more advanced discussions of photosynthesis in plant biology (botany) courses.


  • Develop a hypothesis based on observations.
  • Diagram the process of photosynthesis.
  • Analyze the interactions between the different processes happening during photosynthesis.
  • Apply understanding of photosynthesis to experimental data analysis.


photosynthesis; chloroplasts; plants; herbicides; atrazine; chloroplast; corn resistance;

Topical Areas


Educational Level

High school, Undergraduate lower division, Undergraduate upper division



Type / Methods

Flipped, Role-Play



Subject Headings

Biology (General)  |   Botany / Plant Science  |   Science (General)  |  

Date Posted


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Answer Key

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The following video(s) are recommended for use in association with this case study.

  • The Simple Story of Photosynthesis and Food
    This video explores the relationship between photosynthesis and carbohydrates, starch, and fiber; and how the air we breathe is related to the food we ingest. The video provides a general overview and context for a more detailed discussion of the process in the next video. Running time: 4:00 min. Lesson by Amanda Ooten, animation by Bouncepad Collective, 2013.
  • Photosynthesis
    In this video Paul Andersen reviews photosynthesis including the structure of choloroplasts, the major pigments involved, the light reaction, the Calvin cycle, and strategies for avoiding the problem of photorespiration that evolved in CAM and C4 plants. Running time: 12:26 min. Bozeman Science, 2012.
  • How Atrazine Kills Plants
    This video links the action of the herbicide atrazine to the inhibition of photosynthesis. This video also prepares students to consider how the actions of herbicides influence each of the major components in photosynthesis. Running time: 4:49 min. Created by Angela Hartsock for the National Center for Case Study Teaching in Science, 2016.