5.4 - Research Projects

Think of your own variants on the experiments of this unit. Following are a few ideas to get your mind going.

Bacterial Colonies

Vary the agar concentration of the gel. Try 15 g/l (a harder gel), and 7 g/l (a softer gel). What effect would you predict gel concentration will have on the colony pattern? Is your reasoning affected by questions of nutrient diffusion or bacterial mobility?

Make a photo display showing colony shapes as they change with gel and nutrient concentrations.

Termite Colonies

1. Make a mixture of sand with sawdust (say 10% sawdust by volume) and use this to fill the cell (sawdust is food for termites). Do the termites form a different pattern when they have something to eat?


2. Put a piece of damp paper somewhere in the cell. See what happens if the termites locate this food.


3. Put a thin, damp piece of filter or tissue paper on the bottom plate of the cell, and cover it with sand. Does this alter the foraging pattern?

Root Growth

1. Vary the concentration of the nutrient solution by trying serial dilutions, Take your stock solution and dilute it 1/2, 1/4, 1/8, etc. Based on the research you have done, what effect would you predict the nutrient concentration would have on the root patterns? Explain your reasoning.


2. Would you expect aerating the rhizotron (bubbling water through it) to alter the pattern you observed in the stagnant rhizotron? Does this have anything to do with nutrient diffusion? If you have the materials, follow the rhizotron set-up discussed on our Web site and on the accompanying CD-ROM, and observe root growth under aerated conditions.


3. Speculate how different wavelengths of light might affect root growth? How could this cause changes in the plant's response to nutrients?


4. Would you expect any differences in root growth if you filled a rhizotron with sand or soil or vermiculite?