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Landmark Lesson Plan: Isolation of Phytochrome

Grades: 9-12
Subject areas: Chemistry, botany and physics
Principal author: Erica K. Jacobsen

The following inquiry-based student activities are designed for use in high school lesson planning. The handout, activities, and videos will help students understand the progression of several decades of research leading to the discovery and isolation of phytochrome. The phytochrome system in plants serves as a control mechanism for plant development such as germination and flowering. It is triggered by specific wavelengths of electromagnetic radiation.

The activities are designed as a ready-to-go lesson, easily implemented by a teacher or his/her substitute to supplement a unit of study. In chemistry and botany, the activities relate to making chemical predictions based on observations of plant physiology, then analyzing the accuracy of those predictions. In physics, the activities relate to the electromagnetic spectrum. Other science-related concepts are the importance of collaboration in the scientific process, and how research builds knowledge over long periods of time.

Download the complete lesson plan (PDF).

Resources include:

  • Teacher’s guide: Includes the handout, student activities and answer guide
  • Handout: “Isolation of Phytochrome”
  • Student activities: Includes the four activities described below.

Student activities:

While these activities are thematically linked, each is designed to stand alone as an accompaniment for the handout. Teachers may choose activities based on curricular needs and time considerations. 

  • History Exercise: Chronology of Phytochrome Using the handout, students place phytochrome research events in chronological order on a timeline, illustrating that the research extended over several decades and continues into the future. They also place phytochrome research in the context of other scientific or agricultural developments. (20-25 min.)
  • Scientist Collaboration and Phytochrome Students recognize that many researchers may contribute to a particular discovery or body of knowledge and that a combination of different areas of scientific expertise of researchers can benefit a project. (10-15 min.)
  • The Electromagnetic Spectrum Students identify different areas of the electromagnetic spectrum. They also identify the specific wavelengths associated with the action of phytochrome and interpret what is meant by a photo-reversible reaction. (15-20 min.)
  • Phytochrome Predictions Students examine properties that were predicted for phytochrome even before the pigment was discovered and isolated and relate each predicted property to researcher observations that support it. (20-25 min.)

Mature soybeans.
Understanding the role of phytochrome in soybeans (above) allowed scientists to develop breeds that mature with different photoperiods, thereby increasing supplies of this valuable plant protein.
H. Zell/Wikipedia Commons/CC BY-SA 3.0.
Harry Borthwick (left) and Sterling Hendricks separate light into its various wavelengths to study the effect of each on plant development.
Courtesy Jack Fletcher/National Geographic Creative.