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Unformatted text preview: Plant Science 1203L Laboratory 8 - Seed Dispersal We have studied how plants flower, pollinate, undergo double fertilization and produce fruit and seed. These processes are very similar between the different plant species. However, a plant that simply produces and drops seed where it stands does not have as much opportunity to expand the range of the species unless the seed are in some way transported to new  ground. New ground could be as simple as a field that has been plowed, an area of forest that has undergone a natural disaster such as fire, or truly new ground as is formed by a young volcanic island. In all these scenarios we would expect that plants will eventually appear and grow. Seed dispersal is what allows for this to happen and occurs through a variety of mechanisms that have evolved over thousands of years. Seed dispersal starts first with the fruit and whether it stays on the mother plant and releases the seed (dehiscent fruit) or where the seed stay within the fruit (nondehiscent fruit) which then falls or is released from the plant. Examples of dehiscent fruit are follicles, pods and capsules. Nondehiscent fruit would be characteristic of berries, drupes and nuts. Self-dispersal of seed by plants is termed autochory . While seed dispersal that requires some external factor is term allochory . 1. A demonstration has been set up with pictures, illustrations and real fruit from various plants. Observe and record below whether these fruit are dehiscent or nondehiscent. Dehiscent Nondehiscent 2 -iris, 4 - unknown, 5 - bean 1 - desmodium, 3 beautyberry, 6 - pepper 7 - milkweed, 11 - unknown (capsule) 8 - oak, 9 - solanaceae species, 10 - maple 13 - wild morningglory, 17 sweetgum 12 - crabapple, 14 -unknown samara 18 - four o clock, 19 - catalpa, 20 - datura 15 - dadelion, 16 - cocklebur Seed are further dispersed or scattered by the actions of animals, wind, water and expulsion . These are example of allochory dispersal since they are all factors external to the plant involved in the seed dispersal. Animal dispersal Food Source- In most cases the nourishment provided by the fruit of these plants is the reason for animal attraction. In many regards humans may be the most important animal involved in the world wide dispersal of seeds. Most of the major agronomic crops are grown around the world, but that had their origins from specific continents, most likely would not have spread without the assistance of humans. specific continents, most likely would not have spread without the assistance of humans....
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- Spring '08