Research On The Mechanism Of Ecological Adaptation In The Invasive Plant Xanthium Strumarium

In northeast China, exotic plant Xanthium strumarium has become one of the most serious invasive plants. In order to specified whether Xanthium strumarium can hybridize with native plant Xanthium sibiricum, and whether X. strumarium can lead to genetic erosion on the native species, the fruits of the invasive plant X. strumarium, the native plant X. sibiricum and the reciprocal crossing plants have been studied and the differences between shape of fruits and the germination characteristics have been discussed. It is a comparison of the invasive plant X. strumarium, the native plant X. sibiricum and the reciprocal crossing plants under different nitrogen treatments, that the difference of the biomass accumulation and distribution, growth characteristics and photosynthetic characteristics, to discuss its relationship with invasion of the plants. This research has important theoretical significance, to explore the ecological mechanism of invasive plant X. strumarium, and it was important to the relevant sectors of society, to develop appropriate prevention and control measures for the invasive plant X. strumarium. The conclusions of the research are followed:1. The results showed that:The front view area, perimeter, length and width, fruits weight, germination rate of the reciprocal crossing(Xanthium strumarium×Xanthium sibiricum) and the inbred X. strumarium fruits were significantly higher than the reciprocal crossing (Xanthium sibiricum×Xanthium strumarium) and the inbred X. sibiricum (P<0.05).The perimeter, length and length of thorns of the reciprocal crossing fruits of X. strumarium(Xst♀ ×Xsi♂)were significantly longer than inbred X. strumarium fruits (P<0.05);Both all the area, width, fruits weight, germination rate difference of X. strumarium and (Xst♀×Xsi♂)fruits were not significant (P>0.05);The fruit width and germination rate were significantly different between the reciprocal crossing fruits of X. sibiricum(Xsi♀×Xst♂)and the inbred X. sibiricum fruit on(P<0.05); the width of the reciprocal crossing fruits of X. sibiricum(Xsi♀× Xst♂)is significantly higher than inbred X. sibiricum fruit and its germination rate is lower. Therefore the difference of fruit morphological characteristics between these two plants was significant and the hybrid fruit showed the same result. The reciprocal crossing fruits of X. strumarium(Xst♀×Xsi♂) was significantly higher than the inbred X. strumarium, The difference between the reciprocal crossing seeds of X. sibiricum(Xsi♀×Xst♂)and the inbred X. sibiricums eeds is not significant. The results suggest that hybrid X. strumarium quality of life enhance the invasion, what may occupy space and resources much earlier than X. strumarium and X. sibiricum.2. The stem diameter, total leaf area, total biomass, root biomass and biomass of X. strumarium and the reciprocal crossing plants (Xst♀×Xsi♂) creased significantly(P<0.05), but the plant height and leaf biomass were not affected by the changes of nitrogen content. The root biomass ratio and R/C(Root mass/crown mass) of X. strumarium and the reciprocal crossing plants(Xst♀×Xsi♂) decreased with increasing nitrogen content increased significantly (P<0.05), and leaf area to root mass ratio decreased significantly (P<0.05), fraction of stalk biomass and leaf mass showed a downward trend. The net assimilation rate of X. strumarium was significantly higher than X. sibiricum (P<0.05), but the specific leaf area was significantly lower than X. sibiricum (P<0.05). Relative growth rate, net assimilation rate and mean leaf area ratio of hybrid progeny in different nitrogen treatments among the treatments were higher than female progeny (P<0.05), also the biomass index and growth index of (Xst♀×Xsi♂) plants were higher than (Xsi♀×Xst♂)plants. It follows that:(1) When the nutrient is limiting condition, X. strumarium will distribute more biomass to the root, this distribution may be an ecological strategy which its invasion process adapt to nutrient heterogeneous environment. (2)X. strumarium may increase dry matter accumulation with low light or stalk photosynthesizing. (3) Hybrid progenies of X. strumarium have more strong growth ability and the ability to reproduce than hybrid progenies of X. sibiricum, and it can furtherly strengthen the invasion.