摘要或動機

My Science Fair project last year tested a local native plant for it’s toxic effects on insects (fruit flies), bacteria, fungi, and viruses. The root of the plant Lomatium dissectum, had been used by the Salish People to control lice and other insect pests in horses and cattle. The root was also used to kill fish, which could then be harvested by women and children. The fish killed in this way were not harmful to eat as long as they were consumed soon afterward. I have found also that fishing with the aid of plant toxins was formerly very common in tropical Africa. \r
Lomatium dissectum, grows in dry rocky slopes in conjunction with Sagebrush.\r
Many desert plants produce toxic substances that inhibit the growth of competing plants\r
nearby. This adaptation is called Allelopathy. In a natural ecosystem, Lomatium does not\r
kill fish because it does not grow beside creeks. But this raises the question of whether\r
allelopathic plants growing outside their natural ecosystem are having a toxic effect on\r
animal life. There are introduced invasive weeds that are allelopathic, such as\r
Knapweed,growing near streams. And there are crop plants that are allelopathic – Rye and\r
Alfalfa. Do these “natural herbicides” also kill fish? Walnut trees are allelopathic and\r
compounds from Walnut kill fish.\r
If this effect does go beyond toxicity to other plants, it would be an important\r
consideration to environmental guidelines for private land bordering on streams and\r
rivers. The B.C. Ministry of Environment notes the importance of shade cover for\r
spawning streams. It does not recognize the harmful effects of introduced plants. Yet,\r
when we were purchasing supplies for our Koi Pond the pet supply company offered a list\r
of “Some of the Worst Plants to Have Around Koi”. We do not know if the introduced\r
allelopathic plants are poisoning fish or reducing fish stock by poisoning the food that fish\r
need.\r
Science Fair rules do not allow any research that is expected to have any negative\r
impact on vertebrate animals. Because of this, I have decided to test the effect of\r
allelopathic plants on fruit flies (Drosophila). Fruit flies are similar to fish since, during\r
larva and pupa forms, they live in direct contact with their culture media. I will also be\r
testing the effect of allelopathic plants on Planaria (Turbellaria), an aquatic invertebrate.