Plants are one of the first science topics taught in elementary school. Students plant seeds, grow and measure plants, observe the life cycle, and learn about plant structures and functions. This is in keeping with the National Science Education Standards, which states that students in grades K-4 should understand that plants have basic needs, including air, water, nutrients, and light. Elementary students should also understand plants’ life cycles and that all animals depend on plants.
While these concepts seem easily taught through observation and care for plants, research shows that students do develop significant misconceptions about plants and their needs. Some of these misconceptions may be related to elementary students’ limited classification skills. Many others stem from students’ tendency to give plants human characteristics. Formative assessment can help teachers be aware of student thinking and mindful of their own understanding and explanations of concepts.
We’ve highlighted some common misconceptions about plant classification, plant parts, needs of plants, plant food, and photosynthesis and respiration. Rather than an exhaustive list, this is meant to get you thinking about the ideas and understandings your own students may have. We’ve also provided tools for formative assessment and ideas for planning instruction accordingly.
MISCONCEPTIONS
Plant Classification
Students tend to classify plants based on recognizable characteristics (green, grow in the soil) and parts (stem, leaves, flowers). For example, about half of students in a recent study misclassified a mushroom as a plant because its stalk resembles the stem of a plant.
Students may also not consider trees to be plants. However, this may be due to students’ limited classification skills rather than an understanding of plants. Researchers have found that when classifying animals, elementary students tend to use mutually exclusive groups rather than subsets of a larger group. This may be the same for plants.
| Students may think… | Instead of thinking… |
|---|---|
| Plants are not alive. | Plants are alive, even though they are different from animals and humans in many ways. |
| Trees, grass, vegetables, and weeds are not plants. | Plants have many different characteristics. There are many different types of plants throughout the world. Not all plants have the same structures (stems, leaves, flowers, roots). |
Plant Parts
While most students recognize the stem, leaves, and flowers of plants, fewer identify roots as a common structure. Students may need more experiences observing root systems of various plants.
| Students may think… | Instead of thinking… |
|---|---|
| Plants take in all substances they need to grow through their roots. | Plants take in air through their leaves. Chloroplasts in the plant absorb the sun’s energy for use in photosynthesis. Water and minerals are taken in through the roots. |
| Leaves take in water. | Water is taken in through the roots. |
| Plants get their energy from the soil through roots. | Chloroplasts in the plant absorb the sun’s energy for use in photosynthesis. Water and minerals are taken in through the roots. |
Needs of Plants
Students also tend to give plants human characteristics, especially when it comes to considering what plants need to grow. They may describe plants as eating, drinking, or breathing, or believe that plants need things that are provided by people. This may be an unintended consequence of having students grow and care for plants.
The role of light and nutrients in plant growth seems to be especially difficult for elementary students. For example, students may view sunlight as useful but not essential for plant growth.
| Students may think… | Instead of thinking… |
|---|---|
| Sunlight is helpful but not critical. | Sunlight is essential for plant survival. |
| Sunlight helps plants grow by keeping them warm. | Chloroplasts in the plant absorb the sun’s energy for use in photosynthesis. |
| Soil provides a support structure and food for plants. | Some plants grow in soil-free environments. Plants take up water and minerals from soil, but not “food.” |
| Plants need things provided by people (water, nutrients, light) | While people often care for plants (especially those indoors), plants as a whole are not dependent on people for their needs. |
Plant Food
According to misconception studies, elementary students tend to believe that food must come from outside an organism. While outside sources of food are true for animals, plants produce sugars and starches through the process of photosynthesis. This misconception may be caused by students’ tendency to give plants human characteristics.
Fertilizer, commonly known as “plant food,” may add to the confusion. While this substance is used to enhance plant growth, students may misinterpret the name to mean that it is essential for plant survival.
| Students may think… | Instead of thinking… |
|---|---|
| Plants need “plant food” to eat. | “Plant food” (fertilizer) can provide additional minerals and nutrients for plants. While plants do require these substances for growth, they can fulfill these needs through minerals in the soil and through photosynthesis. Plants do not “eat.” |
Photosynthesis and Respiration
Again, the tendency to give plants human or animal characteristics leads to misconceptions. For example, students often believe that plants perform “reverse breathing” in which they inhale carbon dioxide and exhale oxygen. In reality, plants use and produce both carbon dioxide and oxygen through two processes: photosynthesis and respiration.
Photosynthesis is the process by which plants convert carbon dioxide and water into sugar and oxygen. Photosynthesis requires energy, and a plant’s chloroplasts absorb solar energy to fuel these reactions. Photosynthesis can only happen during the day when sunlight is available.
Respiration, on the other hand, is the breaking down of sugars (and oxygen) to provide energy for plant growth. Respiration also produces carbon dioxide and water, essentially the opposite of photosynthesis. Respiration does not require light and can happen at night.
Plants do release oxygen into the atmosphere, as they produce more than they need during photosynthesis.
The word “respiration” is often used incorrectly to describe breathing, but the two processes are different. Breathing, which occurs in animals, is the process of obtaining oxygen and removing carbon dioxide via lungs or gills. Respiration, as previously described, is the release of energy from food and occurs in both animals and plants.
| Students may think… | Instead of thinking… |
|---|---|
| Plants breathe by inhaling carbon dioxide and exhaling oxygen. | Plants take in air through their leaves. Both carbon dioxide and oxygen are used for different processes. Photosynthesis requires carbon dioxide, while respiration requires oxygen. While plants do release oxygen, it is a by-product of photosynthesis and is not released through breathing. Plants do not breathe. They absorb air through the stomata (pores) in their leaves. |
| Plants obtain their energy directly from the sun. | Energy from the sun allows the plant to carry out photosynthesis and produce sugars. Respiration breaks down these products and provides energy for the plant. |
PROBING FOR STUDENT UNDERSTANDING
What do your students think? Volumes 1, 2, and 3 of Uncovering Student Ideas in Science contain 25 formative assessment probes each to help teachers identify misconceptions. Each volume of this series contains several probes that relate to plants.
Related formative assessment probes in Volume 1 of Uncovering Student Ideas in Science:
“Seedlings in a Jar” asks students to compare the mass of a closed system (jar) before and after seed germination. It can be used to elicit student ideas about germination and plant growth as well as conservation of matter in a closed system.
“Is It Living?” asks students to differentiate between living and nonliving things. It provides insight into the attributes students use to consider if something is or was once living. This may help teachers determine if students consider plants to be living.
Related formative assessment probes in Volume 2 of Uncovering Student Ideas in Science:
“Is It a Plant?” asks students to decide whether a number of items are plants. It provides insight into how students classify plants.
“Needs of Seeds” asks students to determine what seeds need to sprout. It elicits student ideas about germination and seeds.
“Plants in the Dark and Light” asks students to predict how the presence or absence of light will affect the growth of plants. It elicits student ideas about plant growth.
“Is It Food for Plants?” asks students to indicate what plants use as food. It provides insight into students’ understanding of food and plants.
“Giant Sequoia Tree” asks students to decide where the matter in a sequoia tree originally came from. It elicits student ideas about plant growth and transformation of matter.
Related formative assessment probes in Volume 3 of Uncovering Student Ideas in Science:
“Does It Have a Life Cycle?” asks students to determine which organisms go through a life cycle. It can help teachers determine if students recognize that plants undergo life cycles.
TEACHING THE SCIENCE
Based on their misconception study, researchers noted that most elementary students had a well-developed understanding of basic plant characteristics and needs. Researchers thus suggested that teachers move beyond these concepts and do the following:
- Present real examples of nonflowering plants or plants without typical features (stem, leaves, roots).
- Present examples of plants that grow in water without soil.
- Have students germinate seeds with and without nutrients to observe the importance of nutrients in plant growth.
- Have students grow plants in light and in darkness to observe the importance of light in plant survival.
- Allow students to observe a variety of root structures and consider their functions.
- Help students understand ways that plants are different from humans in form and function.
Mindfully use language to promote correct understanding. For example, avoid the use of words such as “food,” “eat,” “drink,” and “breathe” when discussing plants.
National Science Education Standards
Assessing and targeting student misconceptions about plants meet the Life Science Content Standard for grades K-4 and 5-8 of the National Science Education Standards. The entire National Science Education Standards document can be read online or downloaded for free from the National Academies Press web site. Science Content Standards can be found in Chapter 6.
REFERENCES
Barman C., R. M. Stein, S. McNair, and N.S. Barman. 2006. Students’ ideas about plants and plant growth. The American Biology Teacher 68 (2):73–79.
Biology Lessons Part 2: Population Biology. Lesson 2.1: Producers: How Do Plants Grow? Alternative Ideas. http://naturalsciences.sdsu.edu/classes/lab2.1/altern.html
Keeley, P., F. Eberle, and L. Farrin. 2005. Uncovering student ideas in science, vol. 1: 25 formative assessment probes. Arlington, VA: NSTA Press.
Keeley, P., F. Eberle, and J. Tugel. 2007. Uncovering student ideas in science, vol. 2: 25 more formative assessment probes. Arlington, VA: NTSA Press.
Keeley, P., F. Eberle, and C. Dorsey. 2008. Uncovering student ideas in science, vol. 3: Another 25 formative assessment probes. Arlington, VA: NSTA Press.
National Research Council (NRC). 1996. National science education standards. Washington, DC: National Academies Press.
This article was written by Jessica Fries-Gaither. For more information, see the Contributors page. Email Kimberly Lightle, Principal Investigator, with any questions about the content of this site.
Copyright March 2009 – The Ohio State University. This material is based upon work supported by the National Science Foundation under Grant No. 0733024. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work is licensed under an Attribution-ShareAlike 3.0 Unported Creative Commons license.
