Plant Biomass

Victor Sampson and Sharon Schleigh
Type Category
Instructional Materials
Lesson/Lesson Plan , Experiment/Lab Activity
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.




This is one of 30 lessons from the NSTA Press book Scientific Argumentation in Biology.  The lesson engages students in an argumentation cycle in which they evaluate three alternative claims regarding where most of the matter that makes up the stem and leaves of a plant originates.   The lesson engages students by presenting the phenomenon of small sunflower seeds growing into tall flowering plants.  Students are guided to design and carry out an investigation that will allow them to collect evidence needed to construct an argument defending one of the three claims.  As they construct this argument, students build and apply knowledge of photosynthesis and biosynthesis in plants.  This lesson is intended for middle or high school students.  Teachers are encouraged to refer to the preface, introduction, student assessment samples, and appendix provided in the full book for important background on the practice of argumentation and resources for classroom implementation. This resource has also been reviewed for use in high school, see appropriate Performance Expectation for more information.

Intended Audience

Educational Level
  • Grade 6
  • Grade 7
  • Grade 8
  • Middle School
Access Restrictions

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Performance Expectations

MS-LS1-6 Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms.

Clarification Statement: Emphasis is on tracing movement of matter and flow of energy.

Assessment Boundary: Assessment does not include the biochemical mechanisms of photosynthesis.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
The lesson allows students to choose from a list of provided possible explanations and support their choice with evidence and justification. Students then gather their own qualitative and quantitative data that can be used to support their explanation. The activity is based on work done by van Helmont and allows investigation into the source of added mass when a plant grows. If the investigation and measurement is done precisely, the data will show that the soil is not the source of added matter. Students need to consider other possible sources of matter that could add mass to the plant. The students need to be aware of the inputs and outputs of photosynthesis in order to develop their explanation fully. Although the investigation focuses on the matter that cycles to build a plant, the concept of energy flow to drive the matter cycle could be added in as a subsequent activity once the plants have grown for a bit.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
This lesson is centered on argumentation and will engage students in many of the elements of that practice. In particular, this lesson calls on students to evaluate three alternative arguments and to specifically refute one of those in their oral and written argument. Developing a counter argument to refute a claim is a more advanced skill than simply supporting a claim. Therefore, the teacher will need to be prepared to support students in that phase of the lesson. The lesson calls for students to develop and present both oral and written arguments.

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
The investigation in this activity is designed by the students. Students will need to consider various ways to test their ideas, set up the materials, collect data, and what data is needed as evidence for their claim. The teacher will want to facilitate the design to be sure that students investigate in a way that will produce reliable data. If the students are not experienced in designing an investigation, the teacher may wish to provide scaffolding to ensure students’ understanding. Since the data will take several weeks to collect, the teacher will want to ensure good tests by reviewing the methods used by students and taking time to check their experimental setup. This is an opportunity to clarify what good experimental design looks like; including identification of variables and controls as well as the importance of precise measurement and accurate recording of data.

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
This activity is effective at showing the cycling of matter, as the students check the mass of the plants and soil to see that the matter is not coming from the soil but instead, from the carbon dioxide and water molecules. The teacher should take the activity a step further to show the need for light energy to drive the cycling of matter. A suggestion would be to use the plants that are grown to subsequently test the need for light energy to continue growth. This could be achieved through a student-designed investigation that uses one set of the plants. Alternatively, a parallel investigation could be set up at the same time so that the amount of time to run the investigation is minimized.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
The authors cite three crosscutting concepts in the teacher notes, but Energy and Matter offers the most explicit connection to the lesson. The guiding question naturally lends itself to a focus on energy and matter, but the teacher can scaffold student thinking by providing a graphic organizer, like the matter and energy tool in Michigan State University’s Plant Growth and Gas Exchange unit (see page 3 here: ). The teacher should also guide students to focus on energy and matter throughout their discussions and writing.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This lesson was designed explicitly to address the three dimensions of the Framework for K-12 Science Education. The lesson engages students in using science and engineering practices, crosscutting concepts, and disciplinary core ideas to develop an explanation to answer the following guiding question: Where does most of the matter that makes up the stem and leaves of a plant come from? The opening scenario presents the phenomenon of sunflower seeds growing into tall adult plants. This lesson calls for student to begin with two- to three-day old plants although it may be a beneficial experience for students to germinate the plants from seeds. Teachers are also advised to familiarize themselves with Sampson and Schleigh's argumentation framework, suggested teacher behaviors, and assessment approaches before implementing this lesson in the classroom. The lesson resources do not include instructional materials that directly present the core concepts targeted by the lesson. Rather, the teacher will need to facilitate that learning within the argumentation cycle.

  • Instructional Supports: The growth of plants from seeds will be familiar to many students, but germinating seeds in class and using a plant from students’ local environment might enhance relevance of the phenomenon. The preface, introduction, assessment chapter, and appendix of the full book provide critical instructional support information for teachers who wish to implement this lesson. Successful implementation requires skillful facilitation by the teacher throughout the argumentation cycle. Students and teachers will develop the needed skills over time and with the implementation of multiple argumentation cycles. The book does not provide guidance for teachers to support differentiated instruction.

  • Monitoring Student Progress: Constant monitoring and feedback are built into the Sampson and Schleigh's argumentation framework, but they rely on skillful teacher interactions with students. Supportive questioning is critical to student success in this and similar lessons. It is important to monitor and provide feedback to students as they construct initial arguments, present and critique arguments, and draft final written arguments. Teachers can also model and guide students in providing constructive peer feedback. Optionally, students could be allowed to revise and improve final written arguments based on teacher and peer feedback. In the full book, a rubric is provided, along with a sample student response with feedback based on the rubric.

  • Quality of Technological Interactivity: This is not a technology-based lesson.