TwoOldGuys™ Study Guides
BI-114 BioConcepts for Teachers
Appendix B. Laboratory Exercises
L-4. Lab Exercise 4

How Plants Move Nutrients from Soil to Leaves (& other parts)

Some of the newer resource materials (print and on-line [see footnotes]) for elementary science projects are good, because they meet the requirements of science. By now you are supposed to know that the requirements of science include:
- there must be a stated question
- you must state your guess (hypothesis) at the answer
- there cannot be a inherently correct answer; whatever the student observed is what happened! Whatever actually happened is what should have happened. Otherwise, the exercise is not "discovery."

Unfortunately, even the better resource materials still have a few "demonstrations" [activities without clearly stated questions, and with implied correct answers] which cannot be considered to be discovery-based science experiments. These same resource documents will also include science-themed art projects. The demonstrations can be used as science experiments if you fix the errors, by adding a question and presenting the activity to your students as a true discovery-based experiment. For the science- themed art projects, I know of no way to make such projects into science experiments. This exercise is an example of how to convert a science-themed demonstration to a science experiment.

The original, which I have seen in several publications which are presented as resource materials for science projects suited to the elementary classroom, has neither a question nor a hypothesis, and therefore does not qualify as a science experiment. The project demonstrates that the color of a cut flower can be changed by adding food coloring to the water in the vase. One possibility for converting this demonstration to an experiment would be to ask the question, "do plants carry materials up the stem in the sap?" More specifically, we could even ask, "will a plant carry food coloring up the stem in the sap?"

My experiment, described below, does not address the part of the question about "in the sap." If you wanted to add this part, you would cut the stems below the flowers and observe them with a magnifying glass. I would expect [hypothesis] that the tubes in the stem will also be colored by the food coloring, although I would not expect the rest of the stem to have the color. I have seen a demonstration presented as suitable for the elementary classroom to show that these tube carry sap. They involve cut flowers in vases of water, but with the flower cut off. The author stated that water would ooze out of the tubes as the sap travelled up the stem. As an experiment, I would describe it as suited to grades 7 and up.

intended for grade K (to 4)


  1. Question: Do materials travel up the plant stem?
  2. Hypothesis: materials are carried up the stem by the plant,
    I think I saw this on a television science show.
  3. alternate hypothesis: materials don't travel up the stem.
  4. State what observable event is expected to occur because the hypothesis is true:
    food coloring added to the water in a vase with flowers will move up the stem and dye the flower.

Materials and Methods

Written just like a recipe, in sufficient detail that anyone should be able to duplicate your experiment.


Depending on the age of your students, this may include descriptions, drawings, numbers and graphs, ...


[optional] you may discuss how this changes our concept of how the Universe works? This section could also stand alone as a formal essay as can the introduction.

Works Cited


Two web sites I found by Googling "elementary classroom science projects" that are very good [defined as emphasizing the scientific approach consistent with my version in this text] are as follows:

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