Adaptive Mechanism Of Eupatorium Adenophorum And Invasive Test Into Middle And Lower Reaches Of Yangtze River

Crofton weed (Eupatorium adenophorum), native to Mexico and Costa Rica of South America, is one of a serious invasive weed in southwest China. E. adenophorum can conduct sexual and asexual reproduction at the same time, and adapt easily to heterogeneous environment, and can grow well in the slope, wall, bolt and farmland. However, strong adaptability mechanism of E. adenophorum is still a lack of unified understanding. There have been reported that E. adenophorum was found in Zigui of Hubei province, and had a higher risk of invasion into the middle and lower reaches of Yangtze River revealed by Climex model. Focusing on those problems, a field common-garden were planted in Wuhan; we compared the growth and insect resistance of the old and new populations of E. adenophorum collected from Xichang (2009population and2012population), observed the overwinter conditions of E. adenophorum in Wuhan, studied the native plant Artemisia annua located in Hubei province for the effect of competition of E. adenophorum, compared seed germination characteristics and the growth parameters of E. adenophorum of different altitudes by conducting common garden experiments and a field investigation. The results are as follows:1. E. adenophorum cannot conduct sexual reproduction in Wuhan, but can maintain the population by asexual reproduction; the leaf C/N ratios of E. adenophorum were similar between the new and old populations. However, the specific leaf area (SLA) and leaf dry matter content (LDMC) in the two populations were negative correlation. Crofton weed gained resistance to P. litura gradully which were generalist herbivores with the invasive time increase. Growth parameters which including plant height, stem diameter, specific leaf area were significantly higher in2009population than in2012population, which is a obvious sign of phenotypic plasticity. Based in the above results, we conclude that crofton weed has a risk to invade into the region of middle and lower Yangtze River.2. By using multiple De wit replacement series design method to study the competition relation between E. adenophorum and the native plant Artemisia annua located in Hubei province, results showed:Relative yield (RYg) and relative density (RDg) were equal less than1in mixture sample area between E. adenophorum and A. annua, which implied that the competition between E. adenophorum and A. annua was more than intraspecific competition of E. adenophorum and population expansion of E. adenophorum was restrained when A. annua existed. With the increased of mixture proportion of A. annua RYg and RDg of E. adenophorum were equal gradually down, and stem diameter, branch number and biomass were equal gradually down, when the population density increased under this circumstance of higher mixture proportion of A. annua, root/shoot radio of E. adenophorum had a trend of reducing, but plant height of E. adenophorum had a trend of increasing, which suggested that E. adenophorum had to adjust the allocation of resources model namely the strategy of the ground priority growth in response to stronger pressure of competition of A. annua. Based in the results above, we shoud replace control E. adenophorum with A. annua at the early stages of invasion for having good effect on control of E. adenophorum.3. A field investigation and common garden experiments showed:field investigation in Xichang of Sichuan province found that plant height (PH), stem width (SW), leaf area (LA), leaf dry matter content (LDMC), flowering tiller number (FTN) and floret number of each tiller (FNT) decreased gradually with the increase of the altitude except specific leaf area (SLA) which was positively related with altitude, however, seeds of one number flower(SNF) significantly differed among populations. The seeds increased in width but decreased in weight with the increasing of the altitude. At the different temperatures, same altitude collecting seeds which germination capacity (GC) and germination index (GI) gradually reduced with the decreasing of temperature (T≤25℃), and25℃is the optimum temperature of seed germination. And at the same temperature, different altitude acquisition of seeds germination capacity and germination index were decreased with the increasing of altitude. In the common garden experiments with shoots in5months, PH, SW, LA, LDMC and SLA had the same regular with the field investigation, but branch number (BN) was oppositive with the field investigation, namely the high altitude populations branch number more than low altitude populations branch number. In the common garden experiments with shoots in8months, SW and BN had the different regular with the field investigation except PH, which SW have no significant difference at different altitude populations and BN was most at1735m altitude population. The results showed that E. adenophorum not only through strong phenotypic plasticity adapt to different altitude environments, but also produced certain genetic differentiation in different altitude populations.