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Brazilian elodea, often called Brazilian waterweed, is an underwater plant native to the United States. It was first found in 1839 and has since spread across the country, reaching from one coast to the other. How can one plant spread across the entire continental United States? Since no female elodea exist in the United States it has adapted a form of reproduction called fragmentation. It's a popular form of reproduction among fungus, worms and even some types of bacteria. The downside of this type of reproduction is the fact that there is no diversity. One copy will inherit the exact traits of its parent so there is no difference between the two. One parent's weakness will also be the offspring's weakness as well.
Fragmentation is a type of vegetative plant reproduction. It is a form of asexual reproduction in which a mate is not required to fertilize offspring. Fragmentation involves the splitting into fragments that mature into full adults. One disturbance of a plant can result in a fragment being removed from the parent. The split or fragmenting involves a process called mitosis. Mitosis is the splitting of a nucleus into two nuclei with an identical set of chromosomes, thus producing a copy of itself.
Mitosis works in seven phases. It starts with the interphase and ends with telophase. Throughout these seven phases the cells will begin to copy and divide within the cell into two identical cells. Once mitosis is finished, the cycle ends with the rebuilding of the cell wall, thus dividing the nuclei in what is called cytokinesis and completely forming two individual cells. The importance of mitosis is in the copying of chromosomes. Each copy receives a "memory gene" so that the process may continue in the new plant.
Since elodea live underwater, it's easy to see how quickly a plant like that could spread so fast. A simple stem is broken off and carried away to create an identical plant somewhere else. One plant can easily be spread across an entire body of water from one separated fragment. The problem with plants that reproduce in this way is how dense they can become. They tend to drown out other plant life in their habitat, taking over resources and making them scarce for other life, not to mention the fact they cause costly maintenance for anyone to tend to.