AAAS Conference on Developing Textbooks That Promote Science Literacy

February 27-March 2, 2001
American Association for the Advancement of Science
Washington, D.C.

Student-Focused Curriculum Materials Development: The “Food For Plants” Story

Kathleen J. Roth
Michigan State University
February 25, 2001

Outline

Student-Focused Curriculum Materials Development: The “Food For Plants” Story

Kathleen J. Roth
Michigan State University
February 25, 2001

My experiences as a teacher and a researcher convince me that traditional science textbooks are not useful learning tools for the majority of students. In addition traditional teacher’s guides do not provide sufficient support to help teachers guide students in developing real understandings of science concepts. But textbooks and teacher’s guides can be improved, if we take seriously the research on student thinking and learning about particular ideas in the science curriculum (AAAS, 1993, Chapter 15). This research knowledge about student thinking on specific topics in the science curriculum makes it possible to create curriculum materials that better support students in developing genuine understandings of important science ideas. Researchers working on the Project 2061 Curriculum Materials Analysis Study (Roseman et al., 1999) looked for evidence that curriculum materials were making use of this research base and found scant evidence that such research was playing a central role in the development of science textbooks and teacher’s guides.

There are two purposes for this paper. The first purpose is to describe how my experiences as a teacher and a researcher led me to these conclusions about the limitations and potential of science curriculum materials. The second purpose is to provide examples showing how this research was used to create an alternative text and teacher’s guide, Food for Plants, that addresses some of the Project 2061 curriculum materials analysis criteria. Using research about students’ thinking and learning about how plants get their food, this alternative text and teacher’s guide puts students’ thinking and experiences at the center of the development process. In addition to writing the text, I also taught the unit and did a series of in-depth studies of student learning throughout the unit. This research convinced me of the particular importance of the following Project 2061 criteria in science curriculum materials (see Appendix A for a complete list of the Project 2061 criteria):

Providing a Sense of Purpose

Conveying unit purpose

Justifying lesson sequence

Taking Account of Student Ideas

Alerting teacher to commonly held student ideas

Assisting teacher in identifying own students' ideas

Addressing commonly held ideas

Developing and Using Scientific Ideas -- Building a case

Synthesizing ideas over time

Providing practice

Promoting Student Thinking about Phenomena, Experiences, and Knowledge

Encouraging students to explain their ideas

Guiding student interpretation and reasoning

Encouraging students to think about what they've learned

The theme running through all of these criteria is eliciting and guiding student thinking about particular content ideas. Using knowledge about students’ thinking and learning in science, and about their understandings of plants, in particular, I wrote the Food for Plants student text and teacher’s guide. The materials begin by eliciting students’ ideas and experiences about plants and food. As the unit proceeds, the teacher is supported in continually assessing student thinking and understanding (and misunderstanding) and in guiding and supporting students’ development of important science ideas. The materials are not about presenting content to students; instead, they attempt to convince students through a connected series of activities and experiences that the idea of photosynthesis makes sense. “Convincing” students involves gathering evidence that will challenge them to reconsider and change their common ideas that plants get their food from the soil or from water or from the air. “Convincing” students also involves paying attention to students’ experiences and their ideas, presenting carefully selected and sequenced experiences with phenomena and new ideas, and supporting and guiding students’ attempts to make sense of these experiences. Thus, the materials attempt to engage students in constructing a reasoned understanding about plants and food.

The paper is organized in two major sections. I will first describe key experiences that influenced my curriculum materials development work, which included my experiences as a teacher of science and my work as a researcher studying classroom teaching and learning in science. I will then provide examples from the Food for Plants materials, illustrating how they address the Project 2061 criteria listed above.

Becoming a Curriculum Developer

Roots in Teaching

As a middle school science teacher, I was frustrated with science textbooks. And it was this frustration that eventually led me to develop “alternative” curriculum materials designed to help 5^th-6^th grade students understand how plants get their food.

In my teaching of middle school science, I used two different textbooks, one with my seventh grade life science students and another with my eighth grade earth science students. The earth science text was the kind of text I was familiar with as a student myself—full of text definitions and explanations, words in bold print, diagrams to memorize, end-of-chapter words to define and questions to answer. This text was an interesting and helpful resource to me in planning units of instruction. But I could never figure out a way to make it interesting and helpful to my students. I assigned reading and check-up questions as homework, and my students dutifully (for the most part) answered the questions and defined the words. However, it was clear to me that this text was not communicating clearly to my students. In class, it was as if they had never read the text at all. And it did not seem to help to read the text together in class.

The seventh grade text was quite different from the typical text. This was one of the texts created during the post-Sputnik era of NSF-funded science curriculum development efforts. In fact, this text—Interaction of Man (sic) and the Biosphere (Abraham et al., 1975)—had very little narrative text compared to traditional textbooks. Instead, each chapter or unit started with a “big” question—a question focused around a major theme in biology. For example, the chapter about photosynthesis was framed as an investigation of interactions between plants and the environment. The questions guiding the chapter were: List things “that you think might be involved in this interaction between green plants and their physical environment. How could you determine which things are necessary and which are not necessary for photosynthesis to occur?” (Abraham et al., 1975, p. 28). The rest of the chapter included a series of readings and laboratory activities that were used to help answer the framing question. The lab activities were not optional; they were the core of the text. Students conducted experiments to gather evidence that sunlight and carbon dioxide are necessary for photosynthesis and that sugar and starch are produced in the leaves of the plants. They examined Priestley’s historical experiment with the mouse and a plant under a bell jar to provide evidence that oxygen is produced in photosynthesis. Throughout the chapter, the students are engaged in gathering evidence to “build” a basic equation for photosynthesis:

Green plants + CO2 + light + chlorophyll —produce→ Sugar and starch

Thus the text attempted to build an argument, or case, for the content ideas (see Project 2061 criterion IVa).

This nontraditional text changed my way of thinking about science teaching in three important ways. First, it was the first time I had seen a text attempt to engage students in building an argument. Second, it helped me reimagine science teaching as a process of engaging students actively in building ideas using evidence. In this view, student activity was central in the development of ideas. This contrasted with my assumption that the main part of teaching was the presentation of clear explanations of science content and that student activities were nice extras, thrown in to make things a little more interesting. Third, it helped me understand science in new ways. It shook my belief that content was largely lists of terms to memorize and focused my attention instead on the big ideas in science and their conceptual connections.

But this nontraditional text also posed some problems for me as a teacher. Because I wasn’t having students read traditional text, would they be disadvantaged when they took high school science courses where they would be expected to read content-dense textbooks? Should I use traditional textbooks so that I can help students learn how to use these textbooks? Or should I abandon the textbooks and teach in the ways that seemed to be most effective in helping students understand the science ideas? It was these questions that eventually led me to graduate school and into the world of research.

A Researcher’s Perspective

As a graduate student, I participated in a research study of 5^th grade science teaching and learning (Roth, Anderson, and Smith, 1987; Roth, 1984). As a researcher, I had the opportunity to sit in classrooms with my attention focused on the students: How are they making sense of this lesson, this science activity, this unit of study? I interviewed students at critical points throughout a unit of study about how plants get their food, and analyzed their written responses on pre- and posttests. These experiences in tracing student thinking transformed my views about teaching. Consistent with a large body of research on students’ thinking and learning about science concepts, my own research provided critical insights about why it is so difficult for students to develop useful, conceptual understandings of many of the subjects they are taught in school (Anderson and Roth, 1989; West and Pines, 1985).

Table 1 presents some key findings from this research, comparing the goal conceptions of the unit (those consistent with the thinking of the scientific community) with the experience-based conceptions that students bring to the classroom. These experience-based ideas are often in direct conflict with the scientific conceptions. For example, scientists believe that plants get their food energy by taking non-energy containing matter (water and carbon dioxide) and combining them in the presence of light energy to create high-energy food matter (in the form of sugars and starches). This process is called photosynthesis, and it represents an essential difference between plants and animals. Only plants can make their own food, and all other life ultimately depends on this energy-capturing process done by plants for their own sources of food. ^[1]

However, students cannot see any evidence in their everyday life that plants make their food. Quite to the contrary, they see evidence that plants are like people—they take in food from their environment. They drink water and they suck up nutrients and minerals from the soil. They believe that plants, like people, have multiple sources of food that they take in from their environment. But why do these student conceptions matter in the teaching of science? It matters, because it is not easy for students to give up or change their commonsense ideas about plants. The research shows that students (and adults!) will hang on tenaciously to the ideas they have built from experience. They might memorize a definition of photosynthesis, but this does not fundamentally change the way they think about plants.

Building on Piaget’s ideas about the importance of cognitive conflict in the learning process, Posner, Strike, Hewson, & Hertzog (1982) used research about students’ ideas to develop a conceptual change theory of learning. In their view, there are three conditions that must be met before genuine conceptual change can occur. First, students must find a new idea intelligible; that is, they must be able to understand what the new idea is proposing. Second, they must find the new idea plausible; that is, they must be able to reconcile their own ideas with the new idea. And finally, they must find the new idea fruitful; that is, they must be able to see the usefulness of the new idea in a variety of real-world contexts. If they do not see the usefulness of the new idea, it is not worth the struggle to change conceptions.

In my own research, I watched students in an active science classroom, where both the teacher and the students were enthusiastically engaged in conducting a series of experiments with plants. Using the Science Curriculum Study materials (Knott et al., 1978), the teacher skillfully guided students in collecting data about plants’ growth under varying conditions and supported them in graphing and summarizing data. However, in the end, the students’ posttests were not significantly different from their pretests. Students began the unit holding the belief that “light is needed for plant growth,” and they ended the unit with the same belief. They began the unit asserting that plants get their food from the soil or from the water in the soil, and they ended the unit still clinging to these core beliefs. At best, they also added into their schema the idea that plants could also make their own food. Thus the majority of students did not show significant growth or change in their thinking about plants and food.

I was shocked by these results. I had observed the students actively engaged in the activities, including rich discussions about their explanations of the results. I thought that the teacher had successfully helped them interpret the data in ways that would have convinced them that plants are very different from humans—that they have the unique ability to make their own food out of raw materials (water, sunlight, carbon dioxide). What had gone wrong?

This experience gave me a new appreciation of the difficult challenge both students and teachers face when they are trying to change deeply-held, experience-based ideas that are in conflict with scientific explanations. Those few students who were successful in changing their personal theories and in understanding and accurately using the idea of photosynthesis had to use a variety of higher-level thinking skills. They continually tried to use new information to explain and make predictions about plants and their needs. Often this was a difficult and confusing process, as students encountered areas where their knowledge was incomplete or in conflict with the ideas presented. Such conflicts led to analyses of the differences between them and to restructuring of the student’s personal conceptual frameworks. These students were metacognitively active, monitoring their developing understandings and resolving areas of confusion (“If water isn’t their food, then why does my Mom water her plants?”). In the end, they developed conceptual understandings of photosynthesis that they could use to explain why plants in a cave will die or why we need to water plants and give them sunlight. These students’ conceptual learning was not a straightforward process of hearing a new idea, using it once, and then understanding it. And most students did not go through this process. I wanted to help the less successful students go through that same complex process of conceptual change as the few top students had experienced.

In my initial study of the SCIIS curriculum materials, I believed that the SCIIS activities had laid out a solid plan for “building a case” that plants make their own food. In Posner et al.’s terms, the materials made the ideas intelligible. In this regard, the SCIIS materials met the following Project 2061 criteria for analyzing science curriculum materials:

provided a clear sense of the unit purpose (Ia),
laid out a strategic sequence of activities, each clearly linked to the next (Ic),
included a variety of vivid experiences with phenomena (IIIa and b),
synthesized ideas over time (IVd), and
used the activities to build a case that plants need light, air, and water to make food (Iva).

Examining the materials in the context of the student learning data, however, I developed the hypothesis that the materials had failed to:

take students’ ideas into account (II).
provide enough support to help the teacher guide student interpretation and reasoning of the experiments they conducted.
give students enough practice in using the new ideas in a variety of contexts (IVg).

For my dissertation study, I wrote an alternative science textbook to accompany the SCIIS activities (Roth, 1984). The research goal was to study student thinking as they read about how plants get their food. The study looked at middle school students who were reading traditional textbooks about plants and food as well as students who read the Food for Plants text. I wanted to find out whether students’ processing of text would be any different if the text anticipated and interacted with students’ ideas more explicitly. This led to a decision to provide more opportunities for students to practice using the new ideas.

The results of the study surprised me. I did not expect students to undergo any significant conceptual change from just reading a text. However, the findings were dramatic. Only one student out of 12 students who read the traditional texts used a conceptual change reading strategy and developed a solid understanding of the key concepts. In contrast, 6 out of 7 students using the Food for Plants text used a conceptual change reading strategy and developed a solid understanding of the three key concepts: a) plants make their food (and do not take it in), b) plants need light to make their food, and c) plants get their food ONLY by making it. Similar to the students reading the traditional texts, the students reading the experimental text included students with reading levels ranging from grade 3.4 through post high school.

The dissertation study convinced me of the power of taking students’ ideas seriously in writing curriculum materials. After the completion of my dissertation study, I conducted a classroom-based research study of fifth grade students’ thinking and learning about science across the school year. I took on a teacher-researcher role, teaching the science, using a conceptual change teaching approach, and studying student learning across the school year. The Food for Plants unit was taught in this context. Not only did students demonstrate a high level of conceptual growth during the plants unit in the fall, their knowledge of these concepts remained strong in interviews at the end of the year. Convinced that paying attention to students’ thinking had transformed my teaching and contributed to high levels of student learning, I revised the Food for Plants text, supplementing it with additional activities for students and adding a Teacher’s Guide that paid particular attention to helping teachers to guide student interpretation and reasoning (Project 2061 criterion Vb).

Examples from the Food for Plants Materials

My research and teaching experiences led me to the conclusion that it was essential to plan learning experiences for students (both in curriculum materials and in actual teaching) based on knowledge from research about students’ ideas and thinking about the particular topic being studied. The Food for Plants text and teacher’s guide provides examples of the Project 2061 criteria that I believe are most important in taking students’ ideas seriously in writing curriculum materials.

In this section, I describe the ways I went about writing an alternative text that seriously kept students’ ideas, experiences, and thinking as the central focus in making decisions about activities and tasks for the students and about notes to help the teacher guide and support student learning. The examples are organized around the criteria from the Project 2061 analysis of curriculum materials that I found to be most important in developing a student-centered set of materials:

Providing a Sense of Purpose

Conveying unit purpose

Justifying lesson sequence

Taking Account of Student Ideas

Alerting teacher to commonly held student ideas

Assisting teacher in identifying own students' ideas

Addressing commonly held ideas

Developing and Using Scientific Ideas -- Building a case

Synthesizing ideas over time

Providing practice

Promoting Student Thinking about Phenomena, Experiences, and Knowledge

Encouraging students to explain their ideas

Guiding student interpretation and reasoning

Encouraging students to think about what they've learned

But I want to preface this section with a caveat. It is important to note that only the second Project 2061 criterion for analysis of curriculum materials (Taking account of student ideas) explicitly focuses on taking students’ ideas into account. However, writing the Food for Plants text with a focus on student thinking and learning forced me to consider each Project 2061 criterion from the students’ perspectives. For example, the research studies I had conducted clearly indicated that these concepts about plants and food were not easy for students to grasp and that they needed a lot more practice using and applying new ideas in different contexts (Project 2061 criterion IVa). It was one challenge for students to understand the new idea about photosynthesis (to find the new idea intelligible) (Posner et al., 1982). It was another challenge to find the idea plausible in relationship to their entering ideas—to reconcile or accommodate their ideas about food coming from the soil with ideas about plants making food (photosynthesis). And it was yet another challenge to find the idea useful (fruitful) in a variety of contexts and therefore, worth the struggle to understand. Thus, the Project 2061 criterion, “providing practice” became central in writing this student-focused text. I knew that teachers were not likely to recognize how students need to struggle with new ideas in multiple contexts before they will really understand the new idea. Traditional textbooks communicate that learning happens with one reading and a few follow-up questions. I wanted to challenge this assumption and to help teachers realize how difficult and complex learning about plants can be for students.

NOTE: Cited Food for Plants pages can be seen in full in Appendix E. Teacher pages are located in Appendix F. In the original Food for Plants text, the teacher pages are located opposite the corresponding student pags.

Examples for Providing a Sense of Purpose: Does the material convey an overall sense of purpose and direction that is understandable and motivating to students? Does the material convey the purpose of each lesson and its relationship to others? Does the material involve students in a logical or strategic sequence of activities (versus just a collection of activities)?

Both the student text and the teacher’s guide emphasize the unit purpose. The unit begins with a central question, “How do plants get their food?” Three activities frame this question initially for students and engage them in generating hypotheses about how plants get their food.

In the “Seed and the Log” activity (pp. S5-6), students examine some pine tree seeds and a large piece of a tree trunk. They are asked:

How does such a tiny seed grow into a huge tree with a trunk and branches and needles (or leaves) and many roots? What are YOUR hypotheses about how a TINY seed can change into a HUGE tree? Where does all the stuff in the tree trunk come from? Talk with your partner or group about your ideas. Listen to their ideas.

Then write down your ideas about how a tiny seed can become a huge tree.

Draw a picture showing your ideas about how a tiny seed can become a huge tree.

Tell how your ideas are different from someone else in your group.

The next activity, “Our Inquiry: What is food for plants?” (pp. S7-9), explicitly states the unit questions:

In our investigations about plants we will focus on questions about how plants get their food: What is food for plants? How do plants get their food? How does their food help plants live and grow? Do they need food in the winter? How can plants use food to change from tiny seeds into large plants (bushes, trees, flowers, grasses, etc.)?

The activity continues by providing a scientific definition of food as containing energy that living things need to live and grow. A discussion follows that engages students in thinking about why people cannot live by eating dirt or water alone.

In the next activity, “Beginning Ideas About the Question: What is food for plants?” (p. S11), students are asked to write down their own ideas about how plants get food. They draw arrows on a diagram of a plant to show how food moves inside the plant. The text then guides the teacher and students in having a “scientific discussion” about these hypotheses, again beginning the discussion with reference to the framing, central questions of the unit:

Student Text:
In this unit, we will explore what food is for plants and how plants get their food. We will test our hypotheses to find out how plants get food that contains energy that they can use to live and grow. As we go along, compare what you find out with what you have just written. See how your ideas change and grow. (Student text, p. S12, emphasis added)

Teacher’s Guide:
A Possible Teacher Narrative:
“Let’s see how many ideas, or hypotheses, we have about how plants get their food. I will keep a list of our ideas on the board/overhead/poster. I want you to listen carefully to other scientists’ ideas. Do you have evidence to challenge or support their ideas? Do you agree or disagree? Why? Are you clear about what the other person is saying? Can you ask a question to get clearer about what someone else is saying? (Teacher guide, p. T12, emphasis added)

But the central question is not limited to the introductory lessons of the unit. This question is repeatedly posed to students in each lesson as they accumulate evidence across lessons to support and/or challenge different hypotheses about plants and their food. For example, even the activity titles communicate this ongoing exploration of the question about plants’ source of food:

Activity Six: Are seeds food for plants?
Activity Eight: Is water food for plants? Is soil food for plants? Is sunlight food for plants?
Activity Nine: Dr. Van Helmont – Is soil food for plants?

The entire lesson sequence is designed to address this central question, following a model of science instruction that begins by engaging students in considering the central question and eliciting their ideas. After this initial phase, the instruction moves to an “Explore and Challenge” phase, where students are given opportunities to explore their ideas and to consider challenges to their ideas. “Challenge” activities are designed to produce cognitive conflict—to call students’ attention to ways in which their original hypotheses might be limited. After students’ ideas have been challenged to the point where they are beginning to wonder whether their original hypotheses adequately answer the question, the idea of photosynthesis is introduced to them during the “Explain Scientific Concepts” phase. It is introduced in comparison with the students’ hypotheses, and students are asked to consider whether it makes sense in light of the data gathered so far. In the next phase of instruction, students are given many opportunities to use, or apply, the idea of photosynthesis in different real-world situations. At first, they need strong guidance and support (coaching) from the teacher to reason successfully through these problems. The teacher supports students in reconciling this new idea with their entering ideas. As they become more confident in their understandings of the new concept, students need less and less explicit support from the teacher. Thus teacher support gradually fades. Throughout the unit, there are activities designed to support students in reflecting on their own learning and to raise questions and new connections, explorations.

This learner-centered instructional model is explained to teachers in the introductory pages. It is used to guide the sequence of activities. A chart showing the main instructional function of each activity is included in the introductory pages for the teacher. Activities are listed as falling into one of the following instructional phases:

Establish the Problem and Elicit Students’ Ideas
Explore Activities to Challenge Students’ Ideas
Explain Scientific Concepts
Apply Activities to Practice Using New Concepts in relationship to students’ preconceptions

Examples for Taking Account of Student Ideas
The Food for Plants text addresses all three of the Project 2061 criteria in this category:

Alerting teacher to commonly held student ideas: Does the material alert teachers to commonly held student ideas (both troublesome and helpful) such as those described in Benchmarks Chapter 15: The Research Base?

The introductory pages of the text provide some background information about students’ ideas and the importance of making the students’ ideas central in science teaching. In a section titled, “Starting with the Students: Students’ Ideas about Plants and Ways of Thinking” (pp. 2-8 Teacher Introduction, see Appendix D), the teacher is given a description of the research on students’ ideas about plants and their food. Four specific barriers to students’ developing understanding of photosynthesis are then described: 1) everyday vs. scientific definitions of “food”, 2) the challenge of understanding the abstract concept of energy, 3) the challenge of thinking about invisible particles and processes, and 4) students’ satisfaction with explanations that fall short of explaining “why” or “how”.

Equally important, however, the Teacher’s Guide provides commentary throughout about anticipated student responses. The teacher is given guidance about the significance of different types of anticipated student responses and suggestions for how to react. These comments are highlighted on the Teacher Pages under the heading, “Common Student Responses.” This is a regular feature of the activities, and the anticipated responses focus on “incorrect” responses as much as they do on “correct” responses. Typically, a range of possible student responses is given.

For example, on p. T11, the teacher is provided with a range of possible responses that students might give to the question: “Write down YOUR ideas about [how] plants get their food.” These possibilities (all of them contrast with the goal concept about photosynthesis) include water, soil, plant food sticks, sunlight, or a combination of these. In addition to these common student ideas, the guide provides the teacher with some commentary about the patterns of student responses:

Water is one of the most common responses. Many students list multiple sources of food for plants. Some students tend to think about anything plants need as food for the plant. Others think that whatever plants take into their bodies (“eat”) is food for plants. Still others identify only fertilizers or minerals as food for plants. (T11)

In another example, students dissect seeds and observe the seed parts. They are then asked whether they think the seed is food for the plants (p. S16). A chart of “Common Student Responses and Suggested Teacher Interpretations and Actions” appears on p. T16. This chart suggests to the teacher that students should not be expected at this point to hypothesize that the embryo gets food from the food stored in the cotyledon, or even that the seed is a source of food. Instead of bringing these goal ideas and terms into the discussion, the teacher should let the students use their own ideas and words— referring, for example, to the “baby plant” to describe the embryo. They should also make sure that all students observed the “baby plant” since many are likely to have missed it.

Assisting teacher in identifying own students' ideas: Many questions posed to students in the Food for Plants text are designed to elicit the students’ ideas, so that the teacher can learn about the particular ideas and experiences of his/her own students.

The pretest (Appendix C), along with its associated analysis strategies, is an example of assisting the teacher in finding out about his/her own students’ ideas about plants and how they get their food. The questions are designed to elicit students’ own ideas and experiences. The questions are primarily open-ended questions. Many of them provide scenarios for students to explain. By looking at the pattern of answers across items, the teacher can diagnose each student’s entering ideas about plants and food. For example, a student might give the following pattern of responses, which indicate that she believes that plants have multiple sources of food that they take in from their environment and that anything they take in is food (just like anything humans eat is considered food):

Question	Response
4. Describe what food is for plants	Air, water, soil, stuff in the soil
7. What do you think happened to the seeds [that the man planted in a closet]?	They died. They had food cause they had air and water. But plants need light, too, and they didn’t have light.
9. Draw arrows to show how food moves in a green plant.	[Draws arrows going in the roots and up the plant and also going from the air into the leaves]
11. Most plants get food from…	Soil, air, water
13. Which living things take in their food from their outside world (their environment)?	Both plants and animals
14. Which living things make their own food?	Humans
Circle any of the following that you think is food for plants.	Soil, air, water, fertilizer, oxygen, carbon dioxide, plant food you buy at the store

Addressing commonly held ideas: Does the material attempt to address commonly held student ideas?

Many of the activities in the Food for Plants unit were selected because of their potential to challenge and address particular commonly held ideas that students bring to the science classroom. For example, many students begin the unit believing that plants get food from water or from fertilizers and minerals in the soil. They have watched their parents add both water and “plant food” (bought at the store) to make plants grow better. This is strong evidence to support their ideas that both water and plant food are food for plants! But in fact, the water and the minerals and the fertilizer do not provide food energy