36 research outputs found

    Stochastic flowering phenology in Dactylis Glomerata populations described by Markov chain modelling

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    Understanding the relationship between flowering patterns and pollen dispersal is important in climate change modelling, pollen forecasting, forestry and agriculture. Enhanced understanding of this connection can be gained through detailed spatial and temporal flowering observations on a population level, combined with modelling simulating the dynamics. Species with large distribution ranges, long flowering seasons, high pollen production and naturally large populations can be used to illustrate these dynamics. Revealing and simulating species-specific demographic and stochastic elements in the flowering process will likely be important in determining when pollen release is likely to happen in flowering plants. Spatial and temporal dynamics of eight populations of Dactylis glomerata were collected over the course of two years to determine high-resolution demographic elements. Stochastic elements were accounted for using Markov Chain approaches in order to evaluate tiller-specific contribution to overall population dynamics. Tiller-specific developmental dynamics were evaluated using three different RV matrix correlation coefficients. We found that the demographic patterns in population development were the same for all populations with key phenological events differing only by a few days over the course of the seasons. Many tillers transitioned very quickly from non-flowering to full flowering, a process that can be replicated with Markov Chain modelling. Our novel approach demonstrates the identification and quantification of stochastic elements in the flowering process of D. glomerata, an element likely to be found in many flowering plants. The stochastic modelling approach can be used to develop detailed pollen release models for Dactylis, other grass species and probably other flowering plants

    Rhizobacterial salicylate production provokes headaches!

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    Characteristics of the freshwater cyanobacterium Microcystis aeruginosa grown in iron-limited continuous culture

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    A continuous culturing system (chemostat) made of metal-free materials was successfully developed and used to maintain Fe-limited cultures of Microcystis aeruginosa PCC7806 at nanomolar iron (Fe) concentrations (20 to 50 nM total Fe). EDTA was used to maintain Fe in solution, with bioavailable Fe controlled by absorption of light by the ferric EDTA complex and resultant reduction of Fe(III) to Fe(II). A kinetic model describing Fe transformations and biological uptake was applied to determine the biologically available form of Fe (i.e., unchelated ferrous iron) that is produced by photoreductive dissociation of the ferric EDTA complex. Prediction by chemostat theory modified to account for the light-mediated formation of bioavailable Fe rather than total Fe was in good agreement with growth characteristics of M. aeruginosa under Fe limitation. The cellular Fe quota increased with increasing dilution rates in a manner consistent with the Droop theory. Short-term Fe uptake assays using cells maintained at steady state indicated that M. aeruginosa cells vary their maximum Fe uptake rate (ρmax) depending on the degree of Fe stress. The rate of Fe uptake was lower for cells grown under conditions of lower Fe availability (i.e., lower dilution rate), suggesting that cells in the continuous cultures adjusted to Fe limitation by decreasing ρmax while maintaining a constant affinity for Fe

    Mindful Attention Reduces Linguistic Intergroup Bias

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    A brief mindfulness intervention diminished bias in favor of one’s in-group and against one’s out-group. In the linguistic intergroup bias (LIB), individuals expect in-group members to behave positively and out-group members to behave negatively. Consequently, individuals choose abstract language beset with character inferences to describe these expected behaviors, and in contrast, choose concrete, objective language to describe unexpected behaviors. Eighty-four participants received either mindful attention instructions (observe their thoughts as fleeting mental states) or immersion instructions (become absorbed in the vivid details of thoughts). After instruction, participants viewed visual depictions of an imagined in-group or out-group member’s positive or negative behavior, selecting the best linguistic description from a set of four descriptions that varied in abstractness. Immersion groups demonstrated a robust LIB. Mindful attention groups, however, exhibited a markedly tempered LIB, suggesting that even a brief mindfulness related instruction can implicitly reduce the propensity to perpetuate stereotypical thinking through language. These results contribute to understanding the mechanisms that facilitate unprejudiced thinking
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