Tag Archives: pumpkin tendrils

OS12 Pumpkin Stem Parts

Not all plants have stems. Some plants like dandelions just have leaves. These plants can’t get very big. Stems come between the roots and the leaves letting a plant get big. Let’s see how a stem does this.

Question: How does a stem let a plant get big?

pumpkin vine piece

Materials:

1 pumpkin side vine about 1.5 m long

Knife

Magnifying glass

Jar of water with lots of food coloring (red or blue) in it

 

Procedure:

Step 1: Open your Science Journal, write “Investigation 12” and the date.

Step 2: Cut a side vine off a pumpkin vine

Step 3: Cut off a section of the stem with a leaf on the top end. Put the stem in the jar of water and set it aside overnight.

Step 4: Examine the rest of the side vine. What does it feel like? How long are the stem pieces (internodes) between leaf petioles? What shape is the stem?

split pumpkin stem

Splitting open a pumpkin stem shows it is hollow. The inside is smooth but has cords running the length of the stem.

Step 5: Cut off a piece of stem from between two petioles to examine. Is it solid? Is it the same diameter at both ends? Is it the same all the way around? Try to tear it across. Try to tear it lengthwise. Does the inside feel the same as the outside? What else do you see?

Step 6: Examine the strings and soft parts with the magnifying glass. How many strings are there? Are they all the same? Try to cut some strings lengthwise to examine. [Be very careful not to cut yourself.]

Step 7: Cut open a section of vine so you can see how a leaf petiole joins the stem. Examine how the strings go from the stem into the leaf.

split open stem node

Pumpkin stems are hollow as are the petioles as shows in this cut open view. The white part is solid and will put out an adventitious root.

Step 8: Carefully cut off a tendril and examine it. What does it feel like? Is it hollow? Try to cut it lengthwise and see what is inside it. [Do this carefully.]

Step 9: Carefully cut off a white area from the stem below a leaf (the adventitious root) and examine it. How is it different from the stem?

Step 10: Examine the 5cm at the tip of the vine. Is it like the rest of the vine? What is found at the tip? Carefully cut the parts of the tip open to see what is inside.

pumpkin vine tip

Hidden within the tip of a pumpkin vine tip are all the leaves, flowers and tendrils that will be part of the vine.

Step 11: Examine flower buds on the vine by a leaf. Are the stalks like the vine? Do the cords go into the flower stems? Carefully cut open the flower buds. What is inside the buds?

Step 12: Take the piece of vine out of the food coloring. Cut across the end of the stem above where it was in the water. Can you find food coloring inside the vine?

 

Observations:

Use this section to write down and draw what you see.

 

Stem:

 

cross cut pumpkin stem

A stem cut across shows the five cords as round areas in the stem.

Petiole, Tendril and Stem:

 

Root and Stem:

 

Stem cross section plain (top) and food coloring:

 

Vine Tip:

 

small to bigger pumpkin leaves

Even when small a pumpkin leaf has the shape of a big leaf.

Leaves from the very tip to 5cm back:

 

Tendrils from the very tip and 5cm back:

 

small to larger tendril

A pumpkin tendril begins as a tiny spring then opens into a long whip that coils around whatever it touches.

Male Flower from tip whole (top) then cross section:

 

Female Flower from tip whole (top) then cross section:

 

pumpkin flower buds

Both the small male and female pumpkin flower buds are covered with long silky hairs.

Conclusions:

Compare tearing the stem across and lengthwise. Which way was easier? Why is this way easier?

 

What do you think the cords in the vine stems do?

 

How does the cord pattern change around the petiole? Why do you think the pattern does this?

 

How do the cords affect how the stem crushes?

 

What are the advantages of a hollow stem to the plant?

 

What are the disadvantages of a hollow stem to the plant?

 

split male flower bud

Splitting open a male flower bud shows it is smaller than a female flower bud with only the petals and fused stamens waiting to open into a flower.

Where are the spines found on the stem? What do the spines do for the plant?

 

Why are the parts so small at the tip of the vine?

 

How do you think they get bigger? How can you test your idea?

 

Compare the growing tips of the sprout [from Investigation 10] and the vine. Why do you think a plant only grows longer at the tips?

 

How does a pumpkin plant use tendrils? Why is this important to the plant? [You can go out and look at the tendrils on your pumpkin plant.]

 

split female flower bud

Carefully splitting a female flower bud in half shows he ovules waiting to become seeds and the pistil and petals waiting to open out into a flower.

Look back at Investigation 10. How has the stem changed from that of a sprout?