If you're a high school student with an avid interest in botany, you're already way past the bean-in-the-paper-cup phase, you've done the, "Which fertilizer makes the plants grow best?" experiment to death, and you already know the answers to, "What conditions make seeds germinate fastest?" and, "How well do plants grow if they're missing an important nutrient?" You're ready for something different and more challenging, whether it's for a school project, a science fair project, or for your own interests. Here are several projects that you might try.
SELF-POLLINATION VS. CROSS-POLLINATION
While some plants, such as peas, self-pollinate very well, others are structured in such a way as to assure cross-pollination. What would happen if flowers that usually cross-pollinate were self-pollinated instead? For this experiment, consider using Wisconsin Fast Plants (http://www.fastplants.org/), which carry out their entire life cycle in less than a month if grown under constant lighting. See the Bottle Biology website (http://www.bottlebiology.org/) for plans for an inexpensive growth chamber (http://www.bottlebiology.org/basics/lighthouse.html). The flowers of Fast Plants have long pistils and short stamens, which makes it difficult, if not impossible, for them to self-pollinate. You can easily cross-pollinate the plants by gently touching the flowers with a cotton swab, carrying pollen from flower to flower as an insect would. To self-pollinate the flowers, use a pair of tweezers to remove one ripe anther from a stamen and gently dab it on the pistil of the same flower. Once the plants set seed, wait for the fruits to ripen, then count the seeds in the fruits and examine their quality. Which plants set the most seeds: the cross-pollinated plants or the selfed plants? Was there any difference in the size and development of the seeds? Try germinating the seeds from each set of plants, either on moist soil or moist paper towels. Is there a difference in germination rates?
Because of their rapid life cycle, Wisconsin Fast Plants are also good subjects for plant genetics experiments. The Fast Plants website (http://www.fastplants.org/) describes the various genetic variations available: colors, leaf hair types, tall and dwarf plants. You can use these plants to set up experimental crosses, predict the results, cross the plants, save their seeds, then grow the offspring to test your predictions. While the outcomes of most of these crosses are already well known, see if you can come up with some novel crosses, or try some selective breeding to see if you can enhance a particular trait. If your science teacher has an ultraviolet light, you could see if exposing the young flowers to UV radiation before pollination creates mutations in the ovules or pollen that affect the resulting offspring.
Choose a natural area to study where you can observe native plants. Get a good field guide to plants of that area, and do a thorough census of all the plants you can find within a plot that you mark out within that area. You may want to recruit the help of a professional botanist the first time you visit the area to help you identify the plants. Create a plant list for the area, and determine how much of the area is influenced by each species. There are a number of ways you can do this. One way is to use stakes and string to create a transect across the plot, then list the plants along the transect and count their numbers. Percent cover is another way to determine influence, especially within a forest. A single tree may not touch your transect, but the canopy of the tree may shade the plot. You might compare two plots in two different areas and describe why there are different plants living there, or examine the same plot in different seasons to describe the changes.
NATIVE PLANT LIFE HISTORY
While the whole plant life cycle may seem like elementary school science, many native plants have not been closely studied and there are still mysteries about their life cycle yet to be discovered. Select a seasonal native flowering plant in your area and do a thorough study of the species. Record when the plant first appears, when it flowers, and when it dies back. Observe it frequently during its flowering time to see which insects visit it. See if you can catch some of the insects and remove pollen from them. Under a good microscope, compare the pollen from the insect to the pollen you harvest from the anthers of the flowers. Does the insect actually carry pollen from your chosen species? That's a good indication that the insect is a pollinator of that flower. A professional botanist may be able to suggest several natives in your area that have not been well-studied, and whose pollinator may not be known. You might make new discoveries!
PLANT CLONING EXPERIMENTS
Horticulturists have been cloning plants for years. The easiest way to clone a plant is to take a cutting, dip the cutting in rooting compound, and place the cutting in a sterile growth medium such as perlite or sterile seed-starting mix. Try setting up an experiment with different concentrations of the rooting compound (which can be purchased at a garden center).
Plants can also be cloned from a tissue callus. The techniques go well beyond the scope of this article, but inexpensive tissue culture kits can be purchased from science supply houses such as Boreal Labs (http://sciencekit.com/) or Carolina Biological Supply (http://www.carolina.com/). Once you've tried the basic techniques with the kits, design an experiment of your own. You might change the level of one of the nutrients, or try growing tissue from various garden plants to see if they can be cloned using the same techniques. Check the websites of these companies for even more advanced ideas in botany.