Roots absorb water from the soil and send it to the leaves. To get from the roots to the stems the water must travel through the stems. When the leaves make sugar, they send it to the roots through the stems. Let’s find out how water travels through a stem.
Question: What does a pumpkin sprout stem do?
Sprout stems are mostly a greenish white color. The food coloring makes it easier to see some of the parts of the sprout.
Materials:
2 Sprouted Pumpkin Seeds or the sprouts from Investigation 9
Knife
Razor blade
Magnifying glass
Custard cup
Pint Jar
Water
Food coloring (red or blue)
Procedure:
Step 1: Open your Science Journal, write “Investigation 10” and the date.
Step 2: If you are using new sprouts, not the ones from Investigation 9, you need to put one in a jar of water with food coloring in it just as you did for that Investigation.
A sprout has roots leading into a stem with cotyledons and a true leaf on it.
Step 3: Take the sprout out of the plain water and cut the stem off about 3cm above the roots. Set the top half with the leaves back in the cup of water. Cut the roots off about 1cm down and set the roots back in the cup of water. Carefully split the stem in half lengthwise. Try to cut it down into the root.
Sprout roots are white. Stems are green.
The seed coat is attached where the sprout root and stem meet.
Step 4: Examine the split pieces with the magnifying glass.
Splitting open a sprout stem shows the root part is solid but the stem is hollow.
Step 5: Take the sprout out of the water with food coloring. Cut it off about 3cm above the roots. Set the top half with the leaves back in the water with food coloring. Cut the roots off about 1cm down and set the roots back in the water with the food coloring. Carefully split the stem in half lengthwise. Try to cut it down into the root.
The sprout roots appear blue but the stem doesn’t except where some food coloring got smeared.
Step 6: Examine the split pieces with the magnifying glass.
The blue food coloring moves up through the thin walls of a sprout stem.
Step 7: Take the top piece out of the plain water. Carefully cut a very thin piece, as thin as a piece of paper, off the end of the stem. Place a drop of water on a slide and put the piece on it. Do the same with the top from the water with food coloring in it. Place both tops back in their cups of water.
The food coloring is in special places in the sprout stem. This shows that water moves through a stem in special places, not all over.
Step 8: Examine them through the microscope.
Step 11: Clean the slide and cover slip.
Step 12: Examine the top from the water with the food coloring with the magnifying glass. Try to see where the food coloring goes when it reaches the leaf. What parts can you identify in the growing tip?
Step 13: Discard the pieces of sprouts and clean up.
Observations:
Plain stem:
Describe the outside of the stem
Describe where the stem and root meet
Describe the inside of the stem
Describe where the stem and root meet
Describe and draw what you see in the thin slice
Food colored stem:
Describe the outside of the stem
Describe where the stem and root meet
Describe the inside of the stem
Describe where the stem and root meet
Describe and draw what you see in the thin slice
Iodine turns purple in the presence of starch which is made of sugar. Describe where the iodine turns purple.
Describe where the food coloring goes in as it enters the leaves
Conclusions:
Compare the stem and root parts of the sprouts. Can you tell where one ends and the other begins?
Why would the stems and roots be similar?
Where do you think the water and sugars move through a stem?
Why is it better to have the water and sugars move in special places?
What do you think the other parts of the stem do?
What do you think a stem does? [Think about a tree. Its trunk is a stem.]