Selectivity and functional diversity in arbuscular mycorrhizas of co-occurring fungi and plants from a temperate deciduous woodland

1 The arbuscular mycorrhizal (AM) fungi colonizing plants at a woodland site in North Yorkshire (UK) have been characterized from the roots of five plant species (Rubus fruticosus agg. L., Epilobium angustifolium L., Acer pseudoplatanus L., Ajuga reptans L. and Glechoma hederacea L.), and identified using small-subunit rRNA (SSUrRNA) gene amplification and sequencing. 2 Interactions between five plant species from the site and four co-occurring glomalean fungi were investigated in artificial one-to-one AM symbioses. Three of the fungi were isolated from the site; the fourth was a culture genetically similar to a taxon found at the site. Phosphorus uptake and growth responses were compared with non-mycorrhizal controls. 3 Individual fungi colonized each plant with different spatial distribution and intensity. Some did not colonize at all, indicating incompatibility under the conditions used in the experiments. 4 Glomus hoi consistently occupied a large proportion of root systems and outperformed the other fungi, improving P uptake and enhancing the growth of four out of the five plant species. Only G. hoi colonized and increased P uptake in Acer pseudoplatanus, the host plant with which it associates almost exclusively under field conditions. Colonization of all plant species by Scutellospora dipurpurescens was sparse, and beneficial to only one of the host plants (Teucrium scorodonia). Archaeospora trappei and Glomus sp. UY1225 had variable effects on the host plants, conferring a range of P uptake and growth benefits on Lysimachia nummularia and T. scorodonia, increasing P uptake whilst not affecting biomass in Ajuga reptans and Glechoma hederacea, and failing to form mycorrhizas with A. pseudoplatanus. 5 These experimental mycorrhizas show that root colonization, symbiont compatibility and plant performance vary with each fungus-plant combination, even when the plants and fungi naturally co-exist. 6 We provide evidence of physical and functional selectivity in AM. The small number of described AM fungal species (154) has been ascribed to their supposed lack of host specificity, but if the selectivity we have observed is the general rule, then we may predict that many more, probably hard-to-culture glomalean species await discovery, or that members of species as currently perceived may be physiologically or functionally distinct

United in Separation? Lozi Secessionism in Zambia and Namibia

Secessionism perseveres as a complex political phenomenon in Africa, yet often a more in-depth analysis is overshadowed by the aspirational simplicity of pursuing a new state. Using historical and contemporary approaches, this edited volume offers the most exhaustive collection of empirical studies of African secessionism to date. The respected expert contributors put salient and lesser known cases into comparative perspective, covering Biafra, Katanga, Eritrea and South Sudan alongside Barotseland, Cabinda, and the Comoros, among others. Suggesting that African secessionism can be understood through the categories of aspiration, grievance, performance, and disenchantment, the book's analytical framework promises to be a building block for future studies of the topic

Dynamical simulations of polaron transport in conjugated polymers with the inclusion of electron-electron interactions

Dynamical simulations of polaron transport in conjugated polymers in the presence of an external time-dependent electric field have been performed within a combined extended Hubbard model (EHM) and Su-Schrieffer-Heeger (SSH) model. Nearly all relevant electron-phonon and electron-electron interactions are fully taken into account by solving the time-dependent Schr\"{o}dinger equation for the $\pi$-electrons and the Newton's equation of motion for the backbone monomer displacements by virtue of the combination of the adaptive time-dependent density matrix renormalization group (TDDMRG) and classical molecular dynamics (MD). We find that after a smooth turn-on of the external electric field the polaron is accelerated at first and then moves with a nearly constant velocity as one entity consisting of both the charge and the lattice deformation. An ohmic region (3 mV/$\text{\AA}$ $\leq E_0\leq$ 9 mV/$\text{\AA}$) where the stationary velocity increases linearly with the electric field strength is observed for the case of $U$=2.0 eV and $V$=1.0 eV. The maximal velocity is well above the speed of sound. Below 3 mV/$\text{\AA}$ the polaron velocity increases nonlinearly and in high electric fields with strength $E_0\geq$ 10.0 mV/$\text{\AA}$ the polaron will become unstable and dissociate. The relationship between electron-electron interaction strengths and polaron transport is also studied in detail. We find that the the on-site Coulomb interactions $U$ will suppress the polaron transport and small nearest-neighbor interactions $V$ values are also not beneficial to the polaronic motion while large $V$ values favor the polaron transport