It’s All About the Roots

Online Lesson Plan It’s All About the Roots

Lesson Plan by who has taught science at both the middle school and high school levels for Lincoln Public Schools. She has written assessment and curriculum for LPS and has attained a Level II assessment certification. She has also served as a student teacher supervisor for the University of Nebraska-Lincoln.

 

Subject Area:
Science
Suggested Grade Level:
Grades 9-12
Learning Modality:
Kinesthetic
Multiple Intelligence:
Logical-mathematical & Naturalist
Bloom’s Taxonomy:
Evaluation
What are these educational concepts?What are these educational concepts?

 

Objectives

In this lab, students will:

standards02

  • observe and understand that green plants need certain chemicals to live and grow and those nutrients do not need to come from the soil;
  • and observe the effects of the chemicals Nitrogen (N), Potassium (K), Phosphorus (P), Sulfur (S) and Oxygen (O) on root growth.

Introduction

We all depend on soil for food and many other products. It is important to keep soil fertile and intact. Growing plants remove minerals and nutrients from the soil. When farmers harvest crops, the remove soil nutrients along with the plants. Farmers replace soil nutrients through fertilization and crop rotation. Loss of nutrients is not the only danger to soil. Without proper protection, soil may wash away in rain or blow away in the wind. Soil loss can have devastating effects on food supplies and farmer’s lives. This lab introduces students to a way to grow plants without soil. The effects of soil nutrients will be observed.

Hydroponics, which means “water agriculture,” is the process of growing plants in solutions that contain the minerals the plants need. The access to Carbon, Hydrogen, Oxygen, and Nitrogen occur naturally from the atmosphere and from watering the plant. The primary nutrient Nitrogen is necessary for the formation of amino acids, co-enzymes, and chlorophyll. Phosphorus provides sugar, phosphate and energy production for root growth and flower production. Potassium is necessary for protein synthesis and the manufacturing of sugar and starch. One of the earliest records of people using hydroponics were the floating gardens of the Aztecs.

The Resources

Links from within the Wessels Living History Farm site. [Note that clicking on these links will open a new browser window. Just close it and you’ll be back to this page.] Direct the students to these pages.

Handout resources. You’ll need to download this “Laboratory Report Form” here. Note that this document is in Adobe Acrobat™ format. You can find the Adobe Acrobat Reader program here.

Resources from outside Wessels. Find the article “Water Should Tast Good – To Plants!” by Dr. Cal Herrmann and Lawrence Brook, The Growing Edge, Vol. 1 No 4.

Materials needed for the Experiment

  • Bean seeds (12 per group)
  • Clear, empty, clean gallon plastic jugs with lids (two per group) for mixing solution
  • Epsom salts (magnesium sulfate)
  • Saltpeter (potassium nitrate)
  • Baking powder
  • Household ammonia
  • Sulfate of potash ((optional)
  • Tap water
  • Cookie sheet or other wide, shallow container
  • Paper towels
  • Plastic wrap
  • Small plastic containers (butter dish or other-four per group) to act as the reservoir
  • Thick cardboard squares cut to fit over containers
  • Light source
  • Safety goggles

 

The Process

Roots provide the plant with three essential functions – 1) the uptake of water and nutrients, 2) storage for manufactured materials, and 3) physical support of the plant. Hydroponics is all about healthy roots!

To grow plants without soil, a solution providing essential minerals will need to be prepared. HANDLE THESE ELEMENTAL SALTS WITH CARE! SAFETY GOGGLES ARE REQUIRED AND IT IS BEST TO AVOID CONTACT WITH SKIN.

Add a liter of warm tap water to a clean, plastic gallon jug or other container that can be sealed. Each of the nutrients will be added one at a time. Allow each to dissolve completely before adding the next. A level teaspoon will work for each of the nutrient salts; one-half teaspoon for the ammonia only. A close gram equivalent for the salts is also listed in the table. Using a fertilizer such as Miracle Grow is not advised since it is a supplement for soil-based gardens and does not contain the nutrients essential to the plants. Sulfate of Potash (K2SO4) may also be added (.5g) but the solution will work without it. Remember to clearly label the nutrient solution container. When all salts have dissolved and ammonia added, seal the container and gently shake. Fill the rest of the jug with tap water, seal it, and shake some more. A second labeled gallon jug containing only tap water will also need to be prepared.

 

Substance Chemical Formula Amount
Epsom salts (magnesium sulfate) MgSO4 2.4 grams
Saltpeter (potassium nitrate) KNO 2 grams
baking powder (sodium bicarbonate
+ calcium biphosphate)
NaHCO3
+ CaHPO4
Ammonia NH3

Students will prepare four sets of hydroponic containers per group. Four students to a group are recommended. One control (tap water) will be tested per group. Three hydroponic containers per group will allow for attrition of bean seeds.

Soak about a dozen bean seeds overnight. Line the bottom of the cookie sheet with moist paper towels. Place the bean seeds on the moistened towels and cover with plastic wrap. When the seeds have germinated and have roots several centimeters long, they can be “transplanted” to the lab containers. During this time, students can be reviewing and labeling root structures in their lab notebooks and preparing cardboard covers.

Each cardboard cover will have three holes punched in the shape of a triangle. These will guide the seedling and serve as a prop. A fourth hole should be punched in the center so air can reach the solution. The roots of the bean seedlings will be threaded through each of the three holes in the cardboard. The cardboard will be placed on top of the three chosen containers filled with hydroponic solution and the control filled only with tap water. Remember to place containers under a good source of light. More solution will need to be added as transpiration occurs. You may wish to use rubber bands to hold the cardboard to the container.

Learning Advice

The reservoir can be any type of food container but it is best to use something opaque. Even black plastic film containers can work well. Excluding light prevents algae growth. Students will have the most success by utilizing plants that do not grow tall. This lab requires beans, but houseplants also work well. Some examples are: spider plant and Kolanchoe. Lettuce, marigolds, and zinnias work well also if you wish to use seeds smaller than beans. Plants with adequate light and consistent temperature will grow rapidly. A water pH between 5.5 and 6.5 is also recommended. If roots are in stagnant water, they will die due to lack of oxygen. Encourage students to observe the plant/root growth of other class groups.

Further Exploration:
It may also be interesting to have one or two groups use sand or vermiculite along with the hydroponic solution.

Find out what happens to plants growing in a solution lacking one of the nutrients. Have the groups each omit one nutrient and compare what happens to growth. Discuss what affect the water had as a control. Should the mineral content in the tap water be tested? How does the pH of the water sample compare to the hydoponic solution? How could hydroponics benefit agriculture in the United States or around the world? Have someone research NASA’s use of hydroponics in space.

 

Conclusion of the Lesson

Green plants can manufacture their own food from CO2 and H2O, but like all living things, need certain chemicals to live and grow. Normally plants obtain these chemicals from the soil. In nature, fire and water work together to recharge the soil with nutrients. Wood ash, for example is rich in Potassium. Organic matter in the soil is decomposed into basic nutrient salts providing plant food. Rain helps to dissolve the salts, making them available to plants through absorption by the roots. For plants to obtain a “balanced diet,” forests must burn, animals must eat, rain must fall, wood must rot, and microbes in the soil must act. Nature does not always provide ideal conditions, however. This lab offers students a new way to look at plant root growth.

 

Assessment Activity

Complete a Venn diagram comparing and contrasting the root growth in the hydroponic solution vs. the root growth in tap water. Students should list at least three observations in each space.

Use the “Laboratory Report Form” found here. Focus attention on the conclusion section. Remind students that conclusions from an experiment are the observations and opinions formed after investigation and thought. They should not be a summary of what was done during experimentation. Notice that this experiment was meant to expose students to a non-standard way of growing plants. Forming an hypothesis was not one of the main goals. Therefore, the section titled: “Purpose of Experiment” is also important! Teachers can alter the form to include hypotheses if they wish to do so.

If you choose to perform an experiment where students omit one of the chemicals from the solution, have them prepare a bar graph showing root growth in centimeters vs. type of solution. Bar graphs axes should be labeled correctly and graphs posted. A bar graph can also be created showing the results of hydroponic root length vs. tap water.

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