Dynamics Population Occurrence Of New Invasive Plant Flaveria Bidentis

To understand the evolution of growth and development, the laboratory test and field test were carried out together to study the relationship between environmental factors and growth development of yellow top weed(Flaveria bidentis (L.) Kuntze)and the dynamic of growth development under natural conditions.Flaveria bidentis seed was able to germinate at 12℃to 42℃. The seeds can't germinate at 10℃and 44℃, the appropriate temperature range for germination and emergence of seeds was 24～42℃, the germination rate and germination index reached the maximum at 36℃. Emergence was the same as the germination. Because of covering soil above the seeds, emergence time was longer than the germination. Emergence optimum temperature is between 24 ~ 40℃. Through the testing of net photosynthetic rate (Pn), metabolic activity of Flaveria bidentis in different development stage at different temperature, metabolic activity in flowering stage and in seeding stage were stronger at temperature range of 28℃to 40℃.Seed can't sprout under the continuously dark condition, but with light, the germination rate is very high at different light intensity. This research indicated that the seed was light seed, seed that needs light to sprout.Water also plays a very important role. The results show that the rate of seed germination increases with the increase of soil water content, when the soil water content was 60%, the corrected germination rate reached the maximum, was 34.9%. Different levels of short-term flooding also greatly improve the seed germination rate, indicating that the seed effect on immersion stress-resistant. Test according to different heights and different wind speed on the spread yellow top weed impact results shows that the wind seeds and broken by a proliferation of small branches caused a certain extent. With the distance farther away from the wind-borne seed viability also decreased.The systematically research of the emergence, growth and development of the yellow top weed population shows that the emergence of appropriate conditions in the field include temperature and rainfall. When the temperature rose to 20 ~ 22℃, emergence occurs after the strong rainfall.Taking yellow top weed in the stem 4 pair of real leaves, the branch highly approximately in 5~7 (cm) as the dividing line, yellow top weed growth phase was divided into slow vegetal period and fast vegetal period. And according to a large number of research and study, the number of stem leaf can be judged as an index of the growth development of the yellow top weed. By studying the proportion of plant stem height and real leaf number, populations trunk Leaf plant height and number of trunk ratio, shows that the emergence of early force with strong growth, with strong reproductive ability and a great spread of the threat.The earliest germinating plants start budding on August 14th budding, and start flowering on August 23rd. It needs at least one month for all the buds to flower. As the yellow top weed carries on its reproduction through the seed, therefore grasps the appropriate prevention time, limits the seeds grow becomes the key.