Weedy plants affect the biodiversity and ecosystem function as well as the crop and fodder plant production. However, adequate management requires detailed knowledge of the taxonomic identity of these plants. Here, we focused on a hemiparasitic Pedicularis species(Orobanchaceae), which occurs at high densities and results in significant biomass reductions in forage grasses in Bayanbulak Grassland of Xinjiang. The identity of this target species is not clear, with conflicting reports in publications and in herbarium collections. Hence, clear and management-relevant information on demography and reproductive ecology is difficult to be obtained from the literature. Therefore, we analyzed field and archival materials collected from Xinjiang in order to clarify the identity and distribution of the target species. Morphological analyses suggested that the populations at Bayanbulak Grassland should be Pedicularis kansuensis Maxim. rather than P. verticillata L. which has been accepted in the available literature. Phylogenetic analysis with a combination of three barcodes(mat K, rbc L and trn H-psb A) uniting a clade of P. kansuensis and individuals from Bayanbulak Grassland populations with 100% bootstrap support, confirmed the target species to be P. kansuensis. Anatomical investigations and field observations showed that the target species is an annual or biennial herb, which also fits with the life cycle as P. kansuensis. Based on archive material and field observations, we verified that the distribution of P. kansuensis is mainly concentrated in the Tianshan Mountains of Xinjiang.
SUI XiaolinPatrick KUSSLI WenjunYANG MeiqingGUAN KaiyunLI Airong
Fertilization has been shown to have suppressive effects on arbuscular mycorrhizal fungi(AMF) and root hemiparasites separately in numerous investigations, but its effects on AMF in the presence of root hemiparasites remain untested. In view of the contrasting nutritional effects of AMF and root hemiparasites on host plants, we tested the hypothesis that fertilization may not show strong suppressive effects on AMF when a plant community was infested by abundant hemiparasitic plants. Plants and soil samples were collected from experimental field plots in Bayanbulak Grassland, where N and P fertilizers had been applied for three continuous years for control against a spreading root hemiparasite, Pedicularis kansuensis. Shoot and root biomass of each plant functional group were determined. Root AMF colonization levels, soil spore abundance, and extraradical hyphae length density were measured for three soil depths(0 e10 cm, 10 e20 cm, 20 e30 cm). Partial 18 S r RNA gene sequencing was used to detect AMF diversity and community composition. In addition, we analyzed the relationship between relative abundance of different AMF genera and environmental factors using Spearman's correlation method. In contrast to suppressive effects reported by many previous studies, fertilization showed no significant effects on AMF root colonization or AMF species diversity in the soil. Instead, a marked increase in soil spore abundance and extraradical hyphae length density were observed. However, fertilization altered relative abundance and AMF composition in the soil. Our results support the hypothesis that fertilization does not significantly influence the abundance and diversity of AMF in a plant community infested by P. kansuensis.
Xuezhao WangXiaolin SuiYanyan LiuLei XiangTing ZhangJuanjuan FuAirong LiPeizhi Yang
Haustorium formation is the characteristic feature of all parasitic plants and a vital process for successful parasitism.Previous investigations on haustorium initiation and development are constricted to induced processes by host-derived signals or synthetic analogs.Spontaneous haustorium formation in the absence of host signals,a process representing an early stage in the evolution of parasitic plants,remains largely unexplored.Lack of fast and frequent formation of spontaneous haustoria greatly hinders full understanding of haustorium formation in root hemiparasites.In this study,seedlings of Pedicularis kansuensis Maxim.,a facultative root hemiparasitic species in Orobanchaceae observed to produce many spontaneous haustoria,were grown in autoclaved water agar in the absence of any known haustoriuminducing stimulants.We aimed to test the temporal and developmental pattern of spontaneous haustorium formation.Also,effects of sucrose supply and root contact on spontaneous haustorium formation were tested.Spontaneous haustoria were observed starting from six days after germination,much earlier than previously reported root hemiparasites.A majority of the spontaneous haustoria formed on lateral roots.Percentage of seedlings with spontaneous haustoria was 28.8% when grown on water agar plates,with a mean of four haustoria per seedling two weeks after germination.Haustorium formation by seedlings grown in water agar amended with 2% sucrose was more than twice of those without sucrose amendment.Singly grown seedlings were able to develop spontaneous haustoria at similar levels as those grown with another conspecific seedling.In view of the fast and abundant formation of spontaneous haustoria,P.kansuensis may be developed as an excellent experimental system in future investigations for unraveling endogenous regulation of haustorium initiation and development in root hemiparasitic plants.
