Tag Archives: cotyledon

OS4 Which Way Should a Seed Point

In nature a seed might fall on the ground or get buried in mud or by an animal. When a gardener plants a seed, that person can point the seed any direction. Let’s find out if there is a best way to plant a pumpkin seed.

 

Question: Does it matter which end of a seed points down?

supplies for the Investigation

Materials:

6 Pumpkin seeds

Small clear glass or jar with straight sides

Paper towel

Cardboard

Scissors

 

Procedure:

Step 1: Open your Science Journal, write “Investigation 4” and the date.

Step 2: Cut a strip of cardboard 1.5cm shorter than the glass or the jar shoulder and 2.5cm longer than the circumference of the glass or jar.

Step 3: Roll up the cardboard strip and slip it into the glass or jar to make sure it fits. When you let it go, the cardboard should unroll against the glass. You may have to push it out a little. Take the cardboard out again.

Step 4: Fold the paper towel so it fits around the outside of the cardboard ring.

Step 5: Roll the cardboard and paper towel up and put them into the glass or jar so the paper towel touches the glass. It must be very tight. You may need to fasten the cardboard ring with a paperclip to keep it tight.

pumpkin seeds in jar

The cardboard holds the pumpkin seeds firmly against the glass. The paper towels will pull water up to the seeds. Each seed points a different direction.

Step 6: Carefully slide the pumpkin seeds about half way down between the paper towel and glass so two point in each different direction, up, down and sideways. This can take patience and maybe a thin knife to push the seeds around. The seeds must be at least 3cm from the top and 3cm from the bottom.

Step 7: Pour 2cm water into the glass and set it aside. The water will soak up into the paper towel. Make sure about 1.5 – 2cm of water is left in the jar. You may have to add some water to do this. Cover the glass with plastic wrap or put the lid loosely on the jar and set it aside.

Step 8: Check the seeds everyday until they germinate and start to grow. Draw them in your Journal.

Step 9: After the radicle comes out, watch for the cotyledons. Draw them in your Journal.

 

Observations:

Seed 1: Which direction does it point?

How many days until it germinates?

What does the root do?

What does the cotyledon do?

 

Seed 2: Which direction does it point?

How many days until it germinates?

What does the root do?

What does the cotyledon do?

 

up and down pointing seeds germinate

Radicles start growing down as soon as a pumpkin seed germinates.

Seed 3: Which direction does it point?

How many days until it germinates?

What does the root do?

What does the cotyledon do?

 

Seed 4: Which direction does it point?

 

How many days until it germinates?

What does the root do?

What does the cotyledon do?

 

Seed 5: Which direction does it point?

How many days until it germinates?

What does the root do?

What does the cotyledon do?

 

Seed 6: Which direction does it point?

How many days until it germinates?

What does the root do?

What does the cotyledon do?

 

Conclusions:

What happens to the radicle [baby root] when it starts to grow?

 

Why is it important for the radicle to do this?

 

What do you think causes the radicle to do this?

 

germinating pumpkin seed

A pumpkin sprout comes out of the little flat space at one end of a seed.

What happens to the sprout when it starts to grow?

 

Why is it important for the sprout to do this?

 

What do you think causes the sprout to do this?

 

up and down seed radicles

A radicle must grow around to go down when a pumpkin seed points up. A radicle grows straight down when the seed point down.

Which is the best way to plant a pumpkin seed?

 

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?