Materials Included In Kit

Additional Materials Required

Safety Precautions

Wear chemical splash goggles. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Dispose of all products down the drain according to Flinn Suggested Disposal Method #26b.

Teacher Tips

• The nutrient solutions provided in the kit are in concentrated form and need to be diluted before use. Combine the 250 mL of concentrate with 750 mL of distilled water for 1 L of solution ready for use.

• You may want to cut floaters before the lab setup day. Cut the floater materials into 2½" squares prior to student cutting. This will help eliminate wasteful cutting in the center of the material. If student floaters are not perfect, they will still work to support the seeds.
• Aeration of the roots is critical in the early stages of growth. Rapid cellular respiration requires an adequate supply of oxygen.
• Students are likely to be more impressed by the fact that plants can grow without soil as they are with the experimental results.
• This floater cup setup can be used for many other plant growth experiments of student design. Students might want to determine the effect of adding excess nutrients (fertilizers) to various seed types. What happens if you overfertilize?
• The nutrient solutions used in this kit are a modified Hoagland’s recipe. Many other hydroponic solution recipes are readily available for your own mixing and experimental designs.

Sample Data

Student groups will likely have mixed results nurturing their plants. Students will see the need for five seeds since not all are likely to germinate. The answers to the Questions 1–3 should reflect their actual recorded data and observations. Plants that are not adequately aerated will die because of the lack of oxygen required for cellular respiration in the plant roots. Plants overwatered in the soil likewise will “drown” because of the lack of oxygen to the roots. Plants in the soil and the complete nutrient solution will not be significantly different. Students will enjoy seeing the roots in the hydroponic cups and think the plants look healthier than the soil plants.

The deficiency symptoms likely to occur can be characterized as follows: Calcium deficiency—Terminal bud often dead; young leaves often appearing hooked at their tips; tips and margins of leaves withered; roots often dead or dying. Iron deficiency—Larger veins of the leaves remain green while the rest of the leaf turns yellow, especially in young leaves; leaves very pale in color. The deficiency symptoms might not be apparent in every experiment, but observing all the experiments for the class might help identify these common deficiency symptoms. This might point out the need for a large sample size.

Introduction

What do plants need to grow? Do they need soil? What happens if they do not get all of their required nutrients?

Concepts

• Hydroponics

• Micronutrient
• Nutrient deficiency
• Macronutrient

Background

Plants have been grown in “soil-less” solutions since the mid-1800s. Hydroponics is often described as growing plants in nutrient solutions instead of in soil. It wasn’t until the 1930s, however, that hydroponics received any serious consideration for the commercial growth of plants. Some researchers felt that plant growth in hydroponic solutions was much greater than in soil. As a result, people rushed to invest in hydroponic production facilities. But they soon discovered that the growth of hydroponic plants was no better (and no worse) than soil-grown plants.

Although hydroponics is not as miraculous as first thought, it remains an important research method for studying plant growth. The root environment of the plant is much more easily controlled and regulated and observed in a soil-less setup. Hydroponics has also proven useful in space travel for regulating oxygen levels for astronauts. There are some commercial applications of hydroponics and many people grow soil-less plants as a hobby. Today hydroponics is often defined as crop production without soil. This includes crop growth in sand, gravel, perlite, vermiculite and other homogeneous solid materials.

The mineral elements needed by plants are usually put into two categories: (1) macronutrients, which are used by plants in greater amounts and constitute 0.5% to 3.0% of the dry weight of the plants, and (2) micronutrients, which are needed in small amounts and often constitute only a few parts per million of the dry weight. The macronutrients are nitrogen, potassium, calcium, phosphorous, magnesium and sulfur. Micronutrients include sodium, cobalt, iron, manganese, chlorine, vanadium, silicon, iodine, aluminum and selenium.

Materials

Safety Precautions

Please follow all laboratory safety guidelines. Wear chemical splash goggles and chemical-resistant gloves. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

1. Using the pattern below as a guide, cut three floater rings from the foam floater material.

2. Fill one plastic cup about half-full with potting soil. Plant five wheat seeds evenly spaced as indicated in Figure 2. Press the seeds into the soil so they are about ¼" below the surface of the soil. Water the seeds with about 10 mL of distilled water.

3. Label three plastic cups as follows:

“Complete”
“Minus Calcium”
“Minus Iron”

4. Pour 50 mL of Complete Nutrient solution into the cup labeled “Complete.”
5. Place a foam floater in the cup so that it floats on top of the 50 mL of solution.
6. Place one layer of cheesecloth on top of the floater. Be sure the cheesecloth gets wet in the cutout area of the floater. Push it gently into the liquid.
7. “Plant” five seeds by placing them on top of the cheesecloth in the pattern shown in Figure 3.

8. Place another layer of cheesecloth over the top of the floater so that the seeds are trapped between the two layers of the cheesecloth. Be sure the seeds are in contact with the solution.
9. Repeat steps 4–8 using the Minus Calcium solution and the “minus calcium” cup.
10. Repeat steps 4–8 using the Minus Iron solution and the “minus iron” cup.
11. Place all four cups in a warm, dry location. Check and compare the contents of each cup daily for the next two weeks. On the Hydroponics Worksheet record the appearance of the seedlings in each cup as they germinate and grow.
12. Aerate the roots of the plants in the cups with the floaters each day. Use a separate Beral-type pipet for each solution. Do not interchange the pipets. Either label the pipets or leave them standing in their respective cups by inserting the pipet down the side of the cup. To aerate, force air into the solution below the floater for about a minute each day.
13. After the seeds have germinated and formed roots, allow an air pocket to form between the floater and the surface of the nutrient solution. A part of the roots should still be growing in the solution.
14. Water the soil in the soil filled cup as needed—do not overwater. Replace solutions in the floater cups only as necessary. Do not mix up the solutions.
15. Record all observations on the Hydroponics Worksheet and answer the questions on the worksheet at the conclusion of the experiment.

Student Worksheet PDF

10205_Student1.pdf