Materials Included In Kit

Additional Materials Required

Prelab Preparation

Bean seeds must be soaked overnight the night before the lab. Place approximately 80 seeds in a beaker of water and allow them to sit at room temperature overnight. Seed coats may split as the seeds soak. This will ease the process of removing the seed coat.

Safety Precautions

Encourage students to follow all regular laboratory safety rules and to wash their hands thoroughly with soap and water before leaving the laboratory.

Disposal

Peat pellets may be thrown away in the compost or trash after the completion of the activity according to Flinn Suggested Disposal Method #26a. Unused peat pellets, seeds, and other materials may be stored in a cool, dark place for future use.

Lab Hints

• Enough materials are provided in this kit for 24 students working in pairs or for 12 groups of students. The “planting” portion of this laboratory activity can reasonably be completed in one 50-minute class period. Observations will continue over the next few weeks.
• Remind students to add water to the weighing dishes containing the peat pellets every time they come to lab. If lab only meets once a week, the instructor may need to check the trays every couple days and add water if needed. A layer of water approximately 1 cm deep should be sufficient. Typically, bean seeds will begin to sprout after a few days.
• If time allows, have students observe embryo plants under a stereoscope or magnifying glass.
• The only peat pellet, other than the control, that should result in growth is the “cotyledon with baby plant.” In rare instances, the “baby plant” may sprout.
• Plenty of extra seeds are included in case mishaps occur during splitting.

Teacher Tips

• After completing the lab, students should be familiar with common seed parts. Have students “dissect” seeds from various plants and/or plant various seeds to observe differences in plant development. Have students bring familiar seeds (e.g., orange seeds, apple seeds, peanuts, cashews, acorns, sunflower seeds, avocado pits) to class. Make sure that the seeds are fresh and that they have not been roasted or processed.

• Students may take the lab a step further by removing half of a single cotyledon without disrupting the baby plant. Does growth still occur?
• You may wish to introduce the terms monocot and dicot to the class and compare the difference between these types of plants. Show students a monocot seed such as a corn kernel and have them note differences in structure from the bean seed, which is a dicot.

Answers to Prelab Questions

1.  List the basic parts of a bean seed.

Seed coat, cotyledons and baby plant

2. How does an embryo plant differ from a whole seed?

An embryo plant is all the parts contained within a seed coat. A whole seed includes the seed coat.

3. Briefly hypothesize what purpose each part of the seed serves.

Seed coats provide protection of the embryo plant during dormancy.
Cotyledons provide a source of nutrition to a germinating plant until the plant can photosynthesize to produce food.
Baby plants will develop into the roots and the shoot of the plant.

Sample Data

Answers to Questions

1. What seed parts or combination of seed parts grew?

   The whole seed (control) and the cotyledon with baby plant grew.

2. Which seed parts did not grow?

   The lone cotyledon and the baby plant did not grow.

3. Why were the seed parts that grew able to do so?

   The baby plant is the part of the seed that develops into the roots and shoot of the plant, and is therefore necessary for a developing seed to grow. At least one cotyledon is essential to provide the baby plant with nutrients required for growth to begin. Once roots develop, the plant can obtain water and nutrients from the soil.

4. What role did the whole seeds play in the experiment?

   The whole seeds served as a control group.

5. Were your prelab hypotheses supported by the results of the lab? If not, explain how your results differed.

   Student answers will vary, but should include clarification for any discrepancies in their prelab hypotheses.

Introduction

When a whole seed is planted, growth is typically observed. What would happen if only parts of a seed rather than a whole seed were planted? Would certain seed parts germinate on their own? Investigate what parts of a seed are required for growth.

Concepts

• Plant growth

• Seed parts

Background

Seeds are defined as the fertilized ovules of female plants. Seeds may be found inside fruits, flowers, pods and roots of plants depending on the particular species. Almost every plant begins its life cycle as a seed, making seeds essential to life as we know it on Earth. One of the most notable qualities of seeds is their ability to remain dormant for extended periods. What is in a seed that allows life to eventually begin?

A seed is made up of the seed coat, embryo and endosperm. The embryo consists of cotyledon(s), hypocotyl, epicotyl and radicle. In this activity, the hypocotyl, picotyl and radicle will be collectively referred to as the “baby plant” (see Figure 1). The hypocotyl is the part of the embryo that will develop into the lower stem of the plant. As a bean seed begins to sprout, the hypocotyl will become visible first. The epicotyl portion of the embryo will eventually give rise to mature leaves and upper part of the stem. Cotyledons will develop into the first leaves on many types of plants and may be referred to as the seed leaves on a young plant. The point where the “baby plant” attaches to the cotyledon is called the radicle and will develop into the root of the plant. Water enters the seed coat through a small pore where the cotyledons attach (called the hilum), causing the cotyledons to expand and the seed coat to split open. As the cotyledons swell with water, enzymes within in the cotyledons begin to function. Cotyledons are composed of nutritious tissue called endosperm made of primarily starch but also contain fats (oils) and proteins. For this reason, many seeds have nutritional value to many animals, including humans. Nuts and beans are seeds that humans often consume. In this lab, kidney beans will be dissected and the individual seed parts will be planted to see what is required for a seed to grow.

Materials

Prelab Questions

1. List the basic parts of a bean seed.
2. How does an embryo plant differ from a whole seed?
3. Briefly hypothesize what purpose each part of the seed serves.

Safety Precautions

Please follow all regular laboratory safety guidelines. Wash your hands thoroughly with soap and water before leaving the lab.

Procedure

1. In preparation, fill a plastic weighing dish approximately one-half full with tap water. Place 4 peat pellets into the water. It will take a few minutes for the peat pellets to expand completely.
2. Obtain six soaked bean seeds from your instructor, and place the seeds on a paper towel.
3. Set two of the seeds aside. These will be planted as the controls.
4. Using forceps, peel the seed coat completely off of the four remaining seeds.
5. Carefully separate the cotyledons by gently breaking the hilum, which connects the cotyledons. (One cotyledon will have a baby plant structure and one will not.) Place the four cotyledons with the attached baby plants and the four lone cotyledons into separate piles.
6. Remove the baby plant from two of the seed halves by sliding the tip of the forceps underneath the baby plant, separating it from the cotyledon (see Figure 2).

7. Write “baby plant,” “cotyledon,” “cotyledon with baby plant” and “control” on four different string tags. Number the tags 1–4 and write the date on them as well.
8. Label the four peat pellets by opening the string loop and placing it around each of the peat pellets (see Figure 3). Hang the tags over the dish edge so they remain dry and legible.
9. Use the blunt end of a pen or a pencil tip and make two holes approximately one half an inch apart in each of the four peat pellets (see Figure 3).
10. Plant the seed parts in their respective peat pellets by placing one part in each hole and covering it with a thin layer of soil medium from the peat pellet.
11. If the peat pellets have absorbed all the water in the bottom of the plastic dish, add a thin layer (approximately 1 cm) of water to the tray.
12. Place the dish in an area that is at room temperature or slightly warmer, and which receives sufficient light, as directed by the instructor.
13. Check for growth each time lab meets, or as directed by your instructor, and record observations in the Data Table. Add water as needed to the tray. Note: Keep a thin layer of water at the bottom of the dish containing the peat pellets at all times.
14. Extra cotyledons and seed coats may be thrown away in the trash according to the instructor’s directions. Consult the instructor for storage procedures of materials used in the lab. Please wash hands thoroughly with soap and water before leaving the laboratory.

Student Worksheet PDF

10691_Student1.pdf