The seed ecological mechanism of Xanthium strumarium invasion

Exotic plants Xanthium strumarium in Northeast China has become one of the most serious invasive plants. In order to determine whether it can hybridize with native plants X. sibiricum. Acomparison of invasive plants X. strumarium, native plants X. sibiricumandthe reciprocal crossing fruits has been studied and the differences between fruit and germination characteristics have been discussed. The results showed that the front view area, perimeter, length and width, fruits weight, germination rate and speed of the reciprocal crossing (X. strumarium×X. sibiricum) and the inbred X. strumarium fruits were significantly higher than those of the reciprocal crossing (X. sibiricum×X. 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 those of inbred X. strumarium fruits (P<0.05). Both the area, width, fruits weight, germination rate difference between these two fruits were not significant. The width and germination rate of reciprocal crossing fruits of X. sibiricum (Xsi♀×Xst♂) were significantly different with those of inbred X. sibiricum fruit (P<0.05). The width of the reciprocal crossing fruits of X. sibiricum (Xsi♀×Xst♂)was significantly higher than that of inbred X. sibiricum fruit whereas the germination rate was opposite. Therefore, the difference of fruit morphological characteristics between these two plants and their hybrid was significantly different. The reciprocal crossing fruits of X. strumarium(Xst♀×Xsi♂)was significantly higher than that of the inbred X. strumarium. The difference between the reciprocal crossing seeds of X. sibiricum (Xsi♀×Xst♂) and the inbred X. sibiricum seeds was not significant. The results suggested hybrid improve X. strumarium quality which may occupy space and resources more earlier than X. strumarium and X. sibiricum to increase the chance to invase.