OS2 Germinating Seeds

Investigation 2

What’s In a Pumpkin Seed?

 

Although many creatures eat seeds, the number one reason a plant makes seeds is to grow new plants. Each of the three main parts of a seed has a purpose. Let’s look at these parts and see how each accomplishes its purpose.

Note: Part of this investigation is difficult to do. You may want an adult to use the paring knife to avoid cutting yourself.

 

Question: What are the three parts of a seed?

materials for finding the parts of a seed

Materials:

3 Pumpkin seeds

Metric ruler

Cup of warm water

Custard cup

Paring knife

Magnifying glass

Procedure:

Step 1: Open your Science Journal, write “Investigation 2” and the date. Draw Table 1 in your journal.

measuring dry seeds

Measuring the dry seeds is important so we will know if soaking makes a difference.

Step 2: Measure the length, width and fatness of Seeds 1, 2,and 3 in millimeters. You can use the same method you used in Investigation 1. Record the measurements in Table 1.

soaking seeds

Soaking the pumpkin seeds makes them softer and easier to take apart.

Step 3: Mark 1, 2 and 3 at different spots on the custard cup. Pour water in it and put the 3 pumpkin seeds in the water by their numbers to soak until the seed feels like it has air under the surface and bends a little [about an hour].

Step 4: Take Seed 1 out of the water and dry it. Mark its length, width and fatness below the first marks.

measuring soaked seeds

After the seeds soak, measuring them again shows if they have changed.

Step 5: Take the seed coat off. You may have to cut the tip off with the paring knife. Try to tear the coating. Describe how it feels on the outside and the inside.

Step 6: Look at the inside of the seed. Is it one piece or two? How does it feel? What color is it? The two pieces are called cotyledons or seed leaves.

Step 7: Use the paring knife to cut the blunt end off the cotyledons. Use the paring knife to carefully pry them apart. What do the insides of the cotyledons look like? What do you see at the sharp end of the cotyledons?

Step 8: It’s very hard to do these steps well so repeat them with the other two seeds.

Observations:

Measure the beginning and ending length, width and fatness of each seed. Write the measurements in the table.

 

Table 1:

 table to record measurements

Draw and describe the three parts of the seed: the seed coat, the cotyledons and the plant embryo.

dissected pumpkin seed

Like all seeds, a pumpkin seed has three main parts. Can you spot them?

 

Analysis:

Subtract the ending measurement from the beginning measurement for the length, width and fatness of each seed.

Conclusions:

Did the length, width or fatness of the seeds change? Why do you think this is the case? Why is it important to know if these change?

 

Do you think three seeds is a big enough sample? Why?

 

Why did we soak the pumpkin seeds before trying to cut them open? [Try cutting a dry one open.]

 

labeled seed parts

These are the three parts of a pumpkin seed. The cotyledons contain endosperm a form of starch found in all seeds although all don’t have cotyledons.

What do you think each part of the seed does?

 

When you buy roasted pumpkin seeds, sometimes the seed coats are removed. Why?