| Oxytropis ochrocephala Bunge, which is widely distributed in Northwest China, is one of the major poisonous grass species in our country. O. ochrocephala contains swainsonine, one type of neurotoxin, and cause death of livestocks and great damage to the grassland animal husbandry. However, traditional controlling approaches are prone to damaging the ecological environment of grassland, and therefore research is needed for the development of sustainable methods. In this paper, by studying the seed dormancy breaking mechanism and allelopathy of O. ochrocephala, we wanted to reveal whether seed dormancy and allelopathy contriute to in O. ochrocephala’s fast spread, and provided certain theoretical basis to look for more effective prevention and controlling methods. The main results are as follows:1. Seed dormancy of O. ochrocephala belongs to physical dormancy. The rigid seed coat is mainly responsible for seed dormancy and low germination rate. Treated with concentrated sulfuric acid, fine sand grinding, liquid nitrogen, field burying could effectively break seed dormancy of O. ochrocephala, and significantly increased the germination rate. With the concentrated sulfuric acid treatment, seeds protruded after1day, and germination rate reached84.33%. However, treatments with hot water, alkali, GA3and low temperature stratification showed no significantly effect on germination potential and germination rate.2. High concentration of O. ochrocephala water leaching solution treatment extended seed germination time of Medicago sativa and Lolium perenne, and reduced final germination rate of L. perenne, but not that of M. sativa. At the same time, it showed allelopathic inhibition to plant height and root length of the two kinds receptor herbage. Nontheless, no notable allelopathic effect was observed when low concentration of O. ochrocephala water leaching solution was used, and on the contrary it even had promoting effect. Allelopathic inhibition on root length was stronger than it on plant height. The physiological and biochemical indexes of treated grasses showed similar trend with leaching solution of high and low concentration. In comparison, the allelopathic inhibition effect to L. perenne was stronger than that to M. sativa.3. The effect of O. ochrocephala to plant height, dry weight and chlorophyll of M. sativa in the process of soil decay were studied. It showed that high content of O. ochrocephala processing had allelopathic inhibitory effect, but low content treatment had no effect, even promoting effect. At a3%(m/m) percentage of O. ochrocephala content in the soil, it showed significant inhibition to M. sativa plant height, but not to L. perenne. Although, reduced percentage increased dry weight and chlorophyll (a+b) content of of both M. sativa (at1%) and L. perenne (at1-2%)4. The the relative abundance of some microbial species were different between soil growing O. ochrocephala and control soil, with main variation in iii1-15, Burkholderiales, Xanthomonadaceae, Pseudomonadaceae, Syntrophobacteraceae, Gaiellaceae and Bacillaceae. O. ochrocephala possibly alters the relative abundance of different types of microorganisms and the specificity of the gene expression of them, through the interaction of root secretion to rhizosphere microorganisms, so as to establish a suitable micro-environment for their own growth of microbial communities. This may help O. ochrocephala set up the competitive growth advantage and speed up their spread.5. To conclude, enormous seed number and physical dormancyof O. ochrocephala are beneficial to maintain the soil seed bank, germplasm resource storage and continuation of species. Allelopathy of O. ochrocephala directly or indirectly influenced the growth of other plants. These two aspects are important factors for the rapid spread of O. ochrocephala. |
PDF Full Text Request