Thursday, June 16, 2011

Science: Learning about Plants, Lesson 4: Stems

*This lesson stretched out over several days.

We read the section on p. 10 of What Is a Plant? about stems and discussed it.  I didn't focus on the technical terms, but we did discuss that plant stems help hold a plant up and  have tubes inside them that are used to transport water and food within the plant.  We examined a large-ish stem (some kind of a weed from outside), talking about how strong it was, and then we cut it open to see what was inside (we did a cross-section cut first and then split it down the middle.

Our big experiment medium for this lesson was celery because the tubes in the stem are visible to the naked eye.

We examined a piece of celery, and then we left one uncovered in the refrigerator for a few days to see what would happen.  When it was nice and wilted, we put it in water, and the boys were impressed with how quickly it perked up and became firm again--a great illustration that the piece of celery was transporting the water from the glass through the tubes in its stem.

We also used colored water to dye celery stalks.  We filled some glasses with water, added red, blue, and purple (combining red and blue) food coloring, and then put the celery in the colored water.

Red--you can clearly see where the food coloring has dyed the tubes


After just a few hours, the color was visible at the top ends of the stems and a bit in the leaves.  After 24 hours, it could clearly be seen in the leaves.

Red food coloring + green plant = brown!


We also had fun dyeing carnations.  We bought some white carnations and put them in colored water, and over the next few days we watched the color appear in the flowers.  We also split the stems of two of the carnations and put each part in a different color to see what would happen to the flower.

You can see the split stems here--one was in yellow (looks orange) and purple and the other is in green and red.

One day later: the split-stem flower that was in red and green--you can see both colors

Yellow and purple

Yellow--this was the clear winner all the way through.

After one week (minus the split stems--they wouldn't stand up after a couple of days)
The only thing we haven't done yet that I'd like to do relating to stems is to go out and make some bark rubbings from different trees.  It's just been soooo hot here lately (hovering around 100*, up to 103* a few days).  We'll see if we can work it in later!

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