Do Plants Need Soil?

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Objective

SWBAT explain how plants get what they need to grow.

Big Idea

In this lesson, students will be investigating whether or not plants can grow without soil by watching a video on hydroponics gardening and completing three simple investigations.

Lesson Overview

Inquiry Based Instructional Model

To intertwine scientific knowledge and practices and to empower students to learn through exploration, it is essential for scientific inquiry to be embedded in science education. While there are many types of inquiry-based models, one model that I've grown to appreciate and use is called the FERA Learning Cycle, developed by the National Science Resources Center (NSRC):

1. Focus

2. Explore

3. Reflect

4. Apply

A framework for implementation can be found here

I absolutely love how the Center for Inquiry Science at the Institute for Systems Biology explains that this is "not a locked-step method" but "rather a cyclical process," meaning that some lessons may start off at the focus phase while others may begin at the explore phase. 

Finally, an amazing article found at Edudemic.com, How Inquiry-Based Learning Works with STEMvery clearly outlines how inquiry based learning "paves the way for effective learning in science" and supports College and Career Readiness, particularly in the area of STEM career choices. 

Unit Explanation

In this unit, students will first develop an understanding of the biotic and abiotic factors within ecosystems, the characteristics and classification of living organisms, and how plants and animals obtain and use energy to fulfill their needs. 

Then, students will delve deeper into the NGSS standards by examining the interdependent relationships within an ecosystem by studying movement of matter between producers, consumers, and decomposers by creating models of food chains and food webs.  

At the end of this unit, students will study ways that individual communities can use science ideas to protect the Earth's resources and environment.  

Summary of Lesson

Today, I will open the lesson by watching a video on hydroponics gardening. Students will then explore whether or not plants (such as celery, sweet potatoes, & Indian corn) can grow without soil. At the end of the lesson, students will watch a video that compares the growth of plant from chemically treated sweet potato and an organic sweet potato. 

Next Generation Science Standards  

This lesson will support the following NGSS Standard(s):

5-LS1-1.    Support an argument that plants get the materials they need for growth chiefly from air and water.  

5-ESS3-1.  Obtain and combine information about ways individual communities use science ideas to protect the Earth’s resources and environment.

Scientific & Engineering Practices

For this lesson, students are engaged in the following Science & Engineering Practice:

Science & Engineering Practice 3: Planning and Carrying out Investigations

Students will conduct three investigations to help answer the investigative question, Can plants grow without soil? 

Crosscutting Concepts

To relate ideas across disciplinary content, during this lesson I focus on the following Crosscutting Concept:  

Crosscutting Concept 2: Cause and Effect

Students will begin examining relationships between a plant's growth and it's environment by investigating if plants can grow without soil.

Disciplinary Core Ideas

In addition, this lesson also aligns with the following Disciplinary Core Ideas

LS1.C:  Organization for Matter and Energy Flow in Organisms

Plants acquire their material for growth chiefly from air and water. (5-LS1-1)

LS2.A:  Interdependent Relationships in Ecosystems

The food of almost any kind of animal can be §traced back to plants. Organisms are related in food webs in which some animals eat plants for food and other animals eat the animals that eat plants. Some organisms, such as fungi and bacteria, break down dead organisms (both plants or plants parts and animals) and therefore operate as “decomposers.” Decomposition eventually restores (recycles) some materials back to the soil. Organisms can survive only in environments in which their particular needs are met. A healthy ecosystem is one in which multiple species of different types are each able to meet their needs in a relatively stable web of life. Newly introduced species can damage the balance of an ecosystem. (5-LS2-1)

LS2.B:  Cycles of Matter and Energy Transfer in Ecosystems

Matter cycles between the air and soil and among plants, animals, and microbes as these organisms live and die. Organisms obtain gases, and water, from the environment, and release waste matter (gas, liquid, or solid) back into the environment. (5-LS2-1)

Choosing Science Teams

With science, it is often difficult to find a balance between providing students with as many hands-on experiences as possible, having plenty of science materials, and offering students a collaborative setting to solve problems. Any time groups have four or more students, the opportunities for individual students to speak and take part in the exploration process decreases. With groups of two, I often struggle to find enough science materials to go around. So this year, I chose to place students in teams of three! Picking science teams is always easy as I already have students placed in desk groups based upon behavior, abilities, and communication skills. Each desk group has about six kids, so I simply divide this larger group in half. 

Gathering Supplies & Assigning Roles

To encourage a smooth running classroom, I ask students to decide who is a 1, 2, or 3 in their groups of three students (without talking). In no time, each student has a number in the air. I'll then ask the "threes" to get certain supplies, "ones" to grab their computers, and "twos" to hand out papers (or whatever is needed for the lesson). This management strategy has proven to be effective when cleaning up and returning supplies as well!  

Focus

30 minutes

Lesson Introduction & Goal 

I introduce today's learning goal: I can explain how plants get what they need to grow.

Review

I begin by reviewing yesterday's poster, The Plant System Poster. What do plants need to grow?

Students point out that plants need air because they need carbon dioxide to complete the photosynthesis process. One student explains that plants have stomata in their leaves and that these openings allow carbon dioxide to enter and oxygen to exit.

Next, students explain that plants need water. One student explains that roots absorb water from the soil and that stems transport this water to other parts of the the plant. Another student adds that water helps deliver nutrients to the plant as well.  One student explains that water is also a neccesary ingredient for photosynthesis to take place. 

Students then explain how plants need the sun's light energy because plants use this energy to produce their own food. One student points out that the chlorophyll in plant cells is able to absorb light energy and that's why humans can't make their own energy - because we don't have chlorophyll. 

Celery

To extend student understanding of plant structures, I cut the stalks off a Celery plant and place them in three different colors of water: Celery in Food Coloring. While this is an old trick, students excitedly respond with, "Oh yeah! I've seen this before!" I then ask: What do you think will happen? Students apply their understanding of the function of plant stems and explain that the xylem cells in the stem will transport the water to the leaves. 

I then place the bottom of the Celery in Water and explain that we will come back to this later on today! 

Engage

I want to inspire interest in today's lesson and capitalize on student curiosity, so I pose the following question: We know that plants need air, water, and light to grow, but do plants need soil to grow? Turn and talk! This is a difficult concept for students! I hear some students reflecting upon their experiences where soil wasn't needed for a plant to survive or a seed to grow. Others aren't quite convinced because they know that decomposers recycle needed nutrients back to the soil for plants to use. 

Video

This seems like the perfect opportunity to share the following video on hydroponics farming. At first, we discuss the real world challenge of finding growing space within cities. I explain that people have tried growing gardens on the rooftops, but that soil gardens are often quite heavy. 

After students understand that plants can be grown with just water, I pause the video and ask: What concerns do you have about plants being grown without soil? Students share that soil can be full of nutrients needed for plant growth. We then continue the video to find out ways that hydroponic farmers can still provide plants with nutrients through the water itself (by adding fertilizer or by raising fish in the water as their wastes provide nutrients). 

Do Plants Need Soil?  

Again, I return to the question of the day: Do plants need soil? Turn and talk. This time as I walk around the classroom, students use information from the video to support their arguments, "No because you can grow plants with water. You just have to add nutrients to the water." 

This provides a great transition into our investigations today! 

Explore

30 minutes

Explanation of Investigations

When researching different investigations students can complete to answer the question, Do plants need soil?, I came across three ideas posted on Pinterest (link 1 & link 2). Instead of choosing one of these investigations, I choose to provide students with the opportunity to complete all three! I did this for a couple reasons. First, all of these experiments are pretty simple to complete. Second, the more experiences students have with growing plants without soil, they more they will come to realize that plants get what they need to grow mainly from air and water. 

Set Up

The first investigation has to do with the Celery in Water from earlier in the lesson. This will be a class investigation instead of one that the students set up in teams.

To prepare for the other two investigations that students will complete in teams, I set out the following materials: 

Sweat Potato in Water Investigation Materials

 

Indian Corn in Water Investigation Materials

 

Getting Started

I invite students to get out science journals and to write the investigative question at the top of a new page: Can a plant grow without soil? 

Next, I model how to make a T-chart with three rows (one row for each investigation). On the left side of the chart, we create labeled diagrams of each investigation. On the other side of the chart, students write predictions. 

Here are a few student examples of this process: 

 

Celery Investigation

For the celery investigation, I model how to draw and label the Celery in Water. Students then predict whether or not they think the celery will grown new stems. One student thinks that a new plant will grow. I then question the class: So you're saying that I never have to go to the store again to buy celery? I can just keep cutting off the celery stalks and they'll just keep growing back? This ends up stumping a few students. To my surprise, several students predict that the celery will not grow.

Sweet Potato Investigation

Holding up the materials, I model how to use the toothpicks to suspend the sweet potato in water by poking the toothpicks around the center so it catches on the rim of the jar. Here's what the end result will look like: Sweet Potatoes in Jars. Students immediately begin making connections with potatoes that have grown in their pantries! Then, students predict whether or not the sweet potatoes will actually grow without soil. 

Indian Corn Investigation

Again, I hold up the materials and explain how to place the sweet corn in water (halfway up the sweet corn) inside a baggie. To make this investigation a little different, I decide to let half of the groups (those with red dots on their team labels) to add a daily multi-vitamin to their bags. This is what the corn will look like at the end of today's lesson: Corn in the Window. As students make predictions, I hear some students mention that they think the corn in the vitamin water will grow more, because just like the plants in the hydroponics video, plants that grow in water benefit from the addition of minerals. 

Monitoring Student Understanding

Once students begin setting up their sweet potato and Indian corn investigations, I conference with as many groups as possible. My goal is to support students by asking guiding questions (listed below). I also want to encourage students to engage in Science & Engineering Practice 7: Engaging in Argument from Evidence

  1. What patterns have you noticed? 
  2. Why do you suppose ____? 
  3. What have you found so far? 
  4. Has your thinking changed? 
  5. What evidence do you have? 
  6. How did you decide _____?
  7. What conclusion can you draw about ____?

Student Conferences

During this conference, Making Connections,  I try to encourage the team to consider how this investigation will help help answer the question, Can a plant grow without soil? I love listening to the students explain their thinking and connect the investigation with their own lives. 

Reflect & Apply

10 minutes

Video on Organic Sweet Potatoes

I decide to end today's lesson by discussing the following video. This sweet girl explains how she wasn't able to grow a sweet potato plant from a sweet potato because it was treated with bud-nip. I remember watching this video for the first time and thinking: Oh no! I didn't buy organic sweet potatoes! Then, I realized that this may turn into an even more powerful learning experience for students! 

I stop the video at 2:04 minutes as I don't want to provide students with information that links food with cancer without further research and conversation. 

Following the video, students discuss how some of their predictions have changed. One student points out that our sweet potatoes might not grow... not because of the lack of soil, but because of the sweet potato possibly being treated with bud nip. 

Another student suggests that we should try to grow a plant from an organic sweet potato for comparison purposes. We all agreed that this was a great idea! 

To connect this video with NGSS Standard 5-ESS3-1 (Obtain and combine information about ways individual communities use science ideas to protect the Earth’s resources and environment), I also ask students to discuss the concerns that they have with adding chemicals to food. Students wonder if the chemicals are harmful to humans, especially if sweet potatoes aren't able to grow when these chemicals are added. 

Teacher Note: I know that families can have their own opinions about organic food, so I am careful to encourage a student-led conversation during this time.