Exploring Seed Germination
by Brad Williamson
Seeds are very remarkable. Laying dormant inside the seed is an embryo plant. Packed with the embryo is enough stored chemical energy to power the young seedling until it can capture its own energy from the sun by the process of photosynthesis. The timing of germination or the breaking of the dormancy is important to the success of the young seedling. For instance, milkweed seeds that are produced in late summer and fall are carried on the wind, away from the parent plant. They fall to earth in all sorts of environments. If the seed goes ahead and germinates immediately, the young milkweed plant will not be able to produce flowers and seeds before the onset of frosts and winter (at least in the northern U.S.) Milkweed seeds actually don’t germinate until they have experienced long periods of low temperatures. In the spring when the soil is moist and the soil temperature is warm enough a new generation of milkweed to begin. The seed has to somehow respond to signals in its environment in order to germinate at appropriate times.
Many environmental factors can affect seed germination. Light intensity, day length, night length, light color, water, water quality, gravity, crowding, temperature, nearby plants (by chemical agents), genetics, oxygen availability, seed condition, seed age, seed coat condition, seed size and other environmental conditions can have measurable effects on seed germination. Gardeners, worldwide, have a number of ideas of other environmental factors that may influence germination such as the phases of the moon, tidal effects, and planting with companion seeds. Seed germination is a good topic for scientific exploration since it is easy to observe and there are so many obvious and not so obvious environmental factors that can affect the germination.
In order to germinate and break dormancy a seed has to absorb quite a bit of water. In nature seeds absorb this water from the soil. Planting seeds in pots of soil is certainly one way to study their germination and a lot can be learned with controlled experiments. However, observation of soil germinated seeds is not easy-one can only observe the top half of the newly emerged plant. The newly developing roots are equally important when studying seed germination. The method described here involves germinating seeds on a moist filter paper that has a constant source of water. By germinating seeds on a moist paper the root growth can be observed and measured more easily. Also, large numbers of seeds can be tested in a small amount of space in a short period of time.
You’ll find the rest of the lab in pdf format here: Exploring Seed Germination