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How Do Lichens Drink Water?

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Two Different Ways to Approach this Project

    Let's get introduced to a different way of doing science, and let's use this experiment as the vehicle for doing so.

    "Exploration." You approach something - a lichen or a jungle, and hope that it contains something interesting. Thus, up to this moment you have been thinking that we are going to study lichens and find something interesting about them. Then, perhaps, we will be able to apply our findings to other useful things such as mentioned in the lichen cartoon.

    "Being a tool-user." Now let's start over and do what a great many scientists do: first by asking: "I wish that we could find out how to easily store stem cells and other useful cells and tissues for later use in regenerating organs. I need a tool to do this." One of the highly desirable ways (tools) would be to dry them, which stops metabolism. Later, when needed, they would be rehydrated, and the cells would come back to life! (Don't look so incredulous. Seeds and spores do this all the time!) Of course, if you take a heart or liver and merely let it dry out, the cells die. But maybe there is a trick that can be added to the process. But where to find that trick? Let's take a look at some organisms that sometimes have wet phases in their life, and then suffer prolonged dry periods. Ah, ha! Now you see! Let's look at lichens and see how they might do things - use the lichen as a "tool" for revealing nature's secrets.

    Thus you see the difference in the above two methods. Paraphrasing: in the first, the lichen was the center of the study; and in the second, the process of dessication (drying) becomes the center, and the living thing becomes the tool for studying that process. And perhaps several widely different living things can be tools. Some might be better tools than others.

    But there is still something more to using lichens as a tool for studying dessication and the rehydration. That's right! There are two sequential processes to be studied: dessication and rehydration. You don't need to study both: you might let someone else study one while you study the other. That's what we are going to do here: we will study the rehydration, and we will let someone else (somewhere in the world) work on the dessication if it so happens to strike their fancy. You don't have to solve the whole problem: if many labs each contribute smaller solutions, soon the collected results will solve the big problem. Do science by increments: each person or group can push the cutting edge of science forward a little bit.

A SUGGESTED GENERAL METHOD FOR DOING THIS PROJECT

    Please remember that this experiment has never been done before. Thus this suggestion might not work, or might need some adjustment. Of course, not having been done before means that you cannot find much to read in the library or on the "web." Only after you finish the project, AND publish it for others around the world to read, will there be something in the library and on the "web"!

    Overall, the hypothesis is that lichens are hygroscopic (take water out of the air) - maybe all the time - maybe only on moist nights - maybe only a foggy times. The experiment will be to compare a lichen's weight when it has been soaked in water to be fully hydrated to its weight when it is fully dried out, and to its weight after it has been in a humid environment provided by a closed bottle with some wet paper towels in it.

    If you find that your hypothesis is correct, you will then have the opportunity to investigate if the lichen has any specialized organs that are hygroscopic, or whether the phenomenon is generalized to all parts of the lichen. This is mentioned (and shown in the figure above of the thirsty lichen) because many or all lichens have small droplets of a sticky liquid on them. Perhaps these liquids are highly hygroscopic. (Or they might be a defense against being eaten; or they might be only droplets of waste!) Whatever they are, they must have a function!

What to do:

1. Find a rock-face or very large boulder that has lichens growing on it. Using a paint scraper or putty knife, dislodge several of the larger lichens from the rock surface. Do not use lichens that are growing on tree trunks because you will also pick up a lot of bark, which you are not studying! Observe and make a drawing of any droplets that are on the surface of the lichens. Make a measurement of the diameters of certain identifiable droplets. Note the colors of your lichens. (Camera anyone?)
2. Make small holes in the lichens and thread 24-inch strings through the lichens and tie the ends of the strings together making a large loops. Weigh each of the lichens with their strings to the nearest 0.1 gram
3. Place them face up on a hot, sunny surface for a few hours, and weigh them again. If they become lighter, continue their exposure on the hot surface until they don't lose any more weight. Record that "lightest" weights of each specimen. Record any changes in the droplets that you were watching. Note any color changes.
4. Now put a few crumpled damp paper towels in a large bottle or terrarium. Using the strings, suspend the lichens over but NOT touching the damp paper, and hold them in place by putting the lid on the bottle or terrarium. Set the container near a window where sun NEVER directly comes in.
5. At12 hour intervals, record the lichens' weights. Again, note what is happening to the droplets, and to the color of the overall lichens.
6. You now have lots of data, and it is up to you to figure out how to put it all together and present it. Photographs are always nice to have, and teachers love graphs.