Effect of light intensity on the growth characteristics of Bidens pilosa.
The growth characteristics of invasive species Bidens pilosa in vegetative and reproductive periods under four different relative irradiance 5%, 20%, 40% and 100% were studied in the green house. The results showed that moderate shading was favorable for the growth of the weed's supporting organs and biomass accumulation in vegetative period. However, the weed could grow well under severe shading condition. In the two growth periods, the maximum value of RGR and NAR were found under the full exposure and the minimum value under 5% light intensity; The total biomass was the highest under 40% light intensity in vegetative period and under 100% light intensity in reproductive period respectively, and the lowest one was found under 5% light intensity in both periods; The seedling height, TLA, RMR, R/C, LAR, SLA, and the LARm were more higher under 5% light intensity than that under 100% light intensity; The SBR were higher under 40% and 20% light intensity than that under 5%k and 100% light intensity. The results indicated that B. pilosa had strong plasticity to light in morphology, biomass allocation and growth characteristic, which may be one of the reasons why the weed spread extensively and had strong invasiveness.