At some point in your science education, you'll have an opportunity to experiment with plants. Whether that is by observing the process of germination, the path of roots in search of water, the effects of different inputs on plant growth or pollination, observing plants up close in an experimental setting reveals a lot about the processes of nature.
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When you choose the best plants for your science project, consider the purpose of the experiment. The plants you need vary depending on whether you need to see germination, the development of roots, the growth of the plant or pollination.
Plants for Germination Experiments
If your experiment involves observing the changes in a seed as it germinates, you need seeds that germinate quickly and obviously. It is also an advantage if the seeds can germinate outside of soil (i.e., in a wet paper towel), which allows for a better view of the changes taking place. Larger seeds make the process even more visible.
The best plants for this are often the same seeds you would use in your garden every year. Peas, beans, pumpkins, squash, sunflowers and corn are all large seeds that show signs of germination quickly; between seven to 10 days in ideal conditions, but the seed will show signs of swelling and splitting well before. These will also germinate outside of soil. Smaller garden seeds, like tomatoes and peppers, will also germinate quickly, between five to 10 days in warm conditions.
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Sprouts, usually herbs that are grown to be eaten in their seedling form, are also an excellent option in order to see germination taking place en masse. Popular plants for sprouts include alfalfa, broccoli, cress, onions, chives, beets and radish. Sprouts can also easily germinate outside of soil: they will grow on a wet paper towel in a humid but ventilated plastic container. Just make sure to wash the seeds and sterilize the growing materials beforehand, so as not to grow mold as well.
Plants for Rooting Experiments
While just about any plant will do in showing the development of roots in a science experiment, the fastest results are from bulbs, corms, rhizomes and tubers. All of these are dormant plant parts from which new plants will readily grow when conditions are optimal. Bulbs and corms are thickened and swollen underground parts of the stem, which store fuel like starch to jumpstart plant growth. Rhizomes and tubers are similar, except they are technically part of the roots as opposed to the stem.
Bulbs and corms that are easy to obtain and use include amaryllis, lily, iris, daffodil, cyclamen, crocus and gladiolus. Rhizomes and tubers include potato, yam, ginger, turmeric, sweet potato and dahlia.
An easy experiment to show root development uses a transparent glass container that's three-quarters full of loose gravel and water. Placing a bulb, corm, rhizome or tuber in the gravel and close to the glass allows you to see the development of roots. Once again, take care to keep the experiment clean from the outset to avoid mold. Sealing the container is the easiest way to keep the rhizome or tuber moist without submerging it in water, which can cause it to rot; it is best for the water level to be just below the base of the rhizome or tuber.
Plants for Growth Experiments
In order to test things like the effects of light, fertilizer, water levels and other variables, choose a plant that is fast-growing and quite hardy. Once again, many common garden plants fit the bill, but common choices are beans or vigorous hybrid tomato plants.
Both beans and tomatoes are quick to germinate, and their daily growth is visible with the naked eye. Experiments in changing the direction, intensity or duration of the light source, for example, will be seen quickly in the movements, also known as tropisms, of the plants. Similarly, they will show signs of water and nutrient levels in their leaves quite rapidly.
Plants for Pollination Experiments
Pollination experiments are a bit easier to comprehend because all they require is a plant that flowers, and flowers quickly. Some of the fastest-flowering garden plants include sweet peas, marigolds, nasturtiums, nigella and sunflowers. The father of modern genetics, Gregor Mendel, used garden peas (Pisum sativum) for his experiments because they were easy to hand-pollinate.
Flowering plants can be either self-pollinating or requiring of a pollination partner, which is a different plant of the same species. Some plants have "perfect" or bisexual flowers, which contain both male and female reproductive parts. Others, like squash and cucumbers, have distinct male and female flowers.
Easy pollination experiments can also be done outdoors in the springtime when trees like apples, pears, plums and cherries are in bloom. These flowers very clearly show both male and female reproductive parts.
The plants listed above are merely suggestions: when it comes to school science projects, it can be fun to experiment with more exotic or creative fare.