Rice increases phosphorus uptake in strongly sorbing soils by intra-root facilitation

Upland rice (Oryza sativa) is adapted to strongly phosphorus (P) sorbing soils. The mechanisms underlying P acquisition, however, are not well understood, and models typically underestimate uptake. This complicates root ideotype development and trait-based selection for further improvement. We present a novel model, which correctly simulates the P uptake by a P-efficient rice genotype measured over 48 days of growth. The model represents root morphology at the local rhizosphere scale, including root hairs and fine S-type laterals. It simulates fast- and slowly reacting soil P and the P-solubilizing effect of root-induced pH changes in the soil. Simulations predict that the zone of pH changes and P solubilization around a root spreads further into the soil than the zone of P depletion. A root needs to place laterals outside its depletion- but inside its solubilization zone to maximize P uptake. S-type laterals, which are short but hairy, appear to be the key root structures to achieve that. Thus, thicker roots facilitate the P uptake by fine lateral roots. Uptake can be enhanced through longer root hairs and greater root length density but was less sensitive to total root length and root class proportions.Biotechnology and Biological Sciences Research Council (BBSRC): BB/R020388/

“A very orderly retreat”: Democratic transition in East Germany, 1989-90

East Germany's 1989-90 democratisation is among the best known of East European transitions, but does not lend itself to comparative analysis, due to the singular way in which political reform and democratic consolidation were subsumed by Germany's unification process. Yet aspects of East Germany's democratisation have proved amenable to comparative approaches. This article reviews the comparative literature that refers to East Germany, and finds a schism between those who designate East Germany's transition “regime collapse” and others who contend that it exemplifies “transition through extrication”. It inquires into the merits of each position and finds in favour of the latter. Drawing on primary and secondary literature, as well as archival and interview sources, it portrays a communist elite that was, to a large extent, prepared to adapt to changing circumstances and capable of learning from “reference states” such as Poland. Although East Germany was the Soviet state in which the positions of existing elites were most threatened by democratic transition, here too a surprising number succeeded in maintaining their position while filing across the bridge to market society. A concluding section outlines the alchemy through which their bureaucratic power was transmuted into property and influence in the “new Germany”

OpenSimRoot: widening the scope and application of root architectural models

Research Conducted and Rationale: OpenSimRoot is an open sourced, functional- structural plant model and mathematical description of root growth and function. We describe OpenSimRoot and its functionality to broaden the benefits of root modeling to the plant science community. Description: OpenSimRoot is an extended version of SimRoot, established to simulate root system architecture, nutrient acquisition, and plant growth. OpenSimRoot has a plugin, modular infrastructure, coupling single plant and crop stands to soil nutrient, and water transport models. It estimates the value of root traits for water and nutrient acquisition in environments and plant species. Key results and unique features: The flexible OpenSimRoot design allows upscaling from root anatomy to plant community to estimate 1) resource costs of developmental and anatomical traits, 2) trait synergisms, 3) (inter species) root competition. OpenSimRoot can model 3D images from MRI and X-ray CT of roots in soil. New modules include: 1) soil water dependent water uptake and xylem flow, 2) tiller formation, 3) evapotranspiration, 4) simultaneous simulation of mobile solutes, 5) mesh refinement, and 6) root growth plasticity. Conclusion: OpenSimRoot integrates plant phenotypic data with environmental metadata to support experimental designs and gain mechanistic understanding at system scales

Von der SED zur PDS

UuStB Koeln(38)-910108242 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The optimal root proliferation response in maize growing on low fertility soils

In previous work (Postma et al., 2014, Plant Physiol. 166:590-602), we have argued that the optimal lateral root branching density in maize depends on the relative availability of nitrate and phosphorus, two of the most growth limiting nutrients and strongly differing in soil mobility. We concluded that for nitrate acquisition a low branching density is optimal as it allowed for exploration of a larger soil domain and reduced root competition, while for phosphorus acquisition a greater branching density was optimal as it resulted in the greatest root length duration in the, relatively phosphorus, rich top soil. The lateral root branching density, however, is not constant throughout the root system. Roots are known to proliferate into soil domains with greater nutrient availability. Root proliferation is a much studied, but quantitatively still poorly understood plant response to environmental stress. The question is what is the optimal response, and how is it achieved? How many branches suffice to deplete local nutrient pools at a sufficient rate? Do general, all purpose, near optimal responses exist that can be based on purely local signaling, or is the optimal response depended on complex information integration? We adapted and ran the root architectural model SimRoot to simulate various heterogeneous environments in combination with various root proliferation responses (Figure 1). We simulated root growth responses to local signals (i.e. local nutrient concentrations), which were moderated by a whole plant response (whole plant nutrient status) and integrated across multiple nutrients (N, and P)

The optimal lateral root proliferation response in maize growing low fertility soils

In previous work (Postma et al., 2014), we have argued that the optimal lateral root branching density in maize depends on the relative availability of nitrate and phosphorus, two of the most growth limiting nutrients and strongly differing in soil mobility. We concluded that for nitrate acquisition a low branching density is optimal as it allowed for exploration of a larger soil domain and reduced root competition, while for phosphorus acquisition a greater branching density was optimal as it resulted in the greatest root length duration in the, relatively phosphorus, rich top soil. The lateral root branching density, however, is not constant throughout the root system. Roots are known to proliferate into soil domains with greater nutrient availability. Root proliferation is a much studied, but quantitatively still poorly understood plant response to environmental stress. Roots may increase growth rates, and or the lateral branching density in soil domains with greater nutrient availability, but the question is what is the optimal response, and how is optimality achieved by the plants sensing and regulation mechanisms? How many branches suffice to take advantage of local nutrient pools and how fast should the root system be? Does an optimal response strongly depend on other environmental factors and / or the distribution of soil nutrients in time and space, or do more general, all purpose, near optimal responses exist that can be based on purely local signaling? Is root proliferation a desirable trait for crop nutrient acquisition efficiency, or mostly a competitive trait, undesirable in agriculture? We adapted and ran the root architectural model SimRoot to simulate various heterogeneous environments in combination with various root proliferation responses (Figure 1). We simulated root growth responses to local signals (i.e. local nutrient concentrations), which were moderated by a whole plant response (whole plant nutrient status) and integrated across multiple nutrients (N, and P)

Phenotyping wheat root system architecture for deep rooting traits and greater deep water acquisition as a strategy to escape drought

Deep rooting, as a strategy to avoid drought, has been studied however current technological advances with high field MRI, low field NMR and high throughput root phenotyping methods, allow for a radically new approach and novel insights into how and when deep rooting results in deep water extraction and what traits may influence rooting depth, including tradeoffs such as the aforementioned connection between dwarfing and rooting depth