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Fine-root and mycorrhizal traits help explain ecosystem processes and responses to global change

Fine-root and mycorrhizal traits help explain ecosystem processes and responses to global change | soil science | Scoop.it
Plant roots and soil biota represent integral, yet poorly understood components of terrestrial ecosystems. Fine roots, and often mycorrhizal fungi, are required for effective water and nutrient uptake to support plant growth and provide sources of labile carbon (C) supporting the broader soil microbial community. Functional differences in root and mycorrhizal traits are partly driven by inherent species differences but may also be impacted by the local soil environment and prevailing climate. However, our current knowledge of fine-root and mycorrhizal diversity merely scratches the surface of their complex functions, interactions with other soil biota, and feedbacks on ecosystem processes and community composition (Wardle et al., 2004). In an effort to address these issues, a recent meeting was convened by the Chinese Ecosystem Research Network, in Beijing, with participants from the USA, New Zealand, and Finland.

‘Root systems of perennial plants possess a high degree of complexity and the first step to understanding this complexity is to realize that not all roots and root systems are the same.’

In this report, we discuss two key themes that emerged from the International Symposium on Critical Zone Biochemistry and Belowground Ecological Research. First, we discuss the need to identify broad patterns of root and mycorrhizal trait variation, both across and within species, as an effective means to understand and predict variation in function across species and sites, and through time. Second, we assert that, to fully understand the role roots and mycorrhizal fungi play in ecosystem processes, a broader perspective that relates their function to both short-term activity (e.g. acquisition of soil resources) and long-term changes in ecosystem function and community composition is required. Finally, we emphasize the need for a global effort in root and mycorrhizal research to synchronize methods of data collection and sharing for more powerful comparisons of belowground activity.
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Metabolites | Metabolite Profiling of Root Exudates of Common Bean under Phosphorus Deficiency

Root exudates improve the nutrient acquisition of plants and affect rhizosphere microbial communities. The plant nutrient status affects the composition of root exudates. The purpose of this study was to examine common bean (Phaseolus vulgaris L.) root exudates under phosphorus (P) deficiency using a metabolite profiling technique. Common bean plants were grown in a culture solution at P concentrations of 0 (P0), 1 (P1) and 8 (P8) mg P L−1 for 1, 10 and 20 days after transplanting (DAT). Root exudates were collected, and their metabolites were determined by capillary electrophoresis time-of-flight mass spectrometry (CE-TOF MS). The shoot P concentration and dry weight of common bean plants grown at P0 were lower than those grown at P8. One hundred and fifty-nine, 203 and 212 metabolites were identified in the root exudates, and 16% (26/159), 13% (26/203) and 9% (20/212) of metabolites showed a P0/P8 ratio higher than 2.0 at 1, 10 and 20 DAT, respectively. The relative peak areas of several metabolites, including organic acids and amino acids, in root exudates were higher at P0 than at P8. These results suggest that more than 10% of primary and secondary metabolites are induced to exude from roots of common bean by P deficiency.
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Biswapriya B Misra's curator insight, September 10, 2014 10:55 PM
Root exudates improve the nutrient acquisition of plants and affect rhizosphere microbial communities. The plant nutrient status affects the composition of root exudates. The purpose of this study was to examine common bean (Phaseolus vulgaris L.) root exudates under phosphorus (P) deficiency using a metabolite profiling technique. Common bean plants were grown in a culture solution at P concentrations of 0 (P0), 1 (P1) and 8 (P8) mg P L−1 for 1, 10 and 20 days after transplanting (DAT). Root exudates were collected, and their metabolites were determined by capillary electrophoresis time-of-flight mass spectrometry (CE-TOF MS). The shoot P concentration and dry weight of common bean plants grown at P0 were lower than those grown at P8. One hundred and fifty-nine, 203 and 212 metabolites were identified in the root exudates, and 16% (26/159), 13% (26/203) and 9% (20/212) of metabolites showed a P0/P8 ratio higher than 2.0 at 1, 10 and 20 DAT, respectively. The relative peak areas of several metabolites, including organic acids and amino acids, in root exudates were higher at P0 than at P8. These results suggest that more than 10% of primary and secondary metabolites are induced to exude from roots of common bean by P deficiency.
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A review of the effects of soil organisms on plant hormone signalling pathways

A review of the effects of soil organisms on plant hormone signalling pathways | soil science | Scoop.it

Plants interact with a large number of soil organisms. For a long time, these interactions have been the research area of soil ecologists and trophic relationships and physico-chemical modifications of the soil matrix were generally proposed as mechanisms underlying plant-soil organism interactions. However, some specific symbioses and diseases have been well characterized at the molecular level by plant biologists and microbiologists. These interactions involve a physical contact between soil organism and plant. They are mediated through signal molecules that play upon the different plant hormonal signalling pathways, leading to modifications in plant development and defence. Nowadays, the role of signal molecules emerges as an important feature of interactions between plants and free-living soil organisms. In this review we discuss genetic and physiological evidences of hormone signalling involvement in plant response to physically associated but also free-living soil organisms, for very different taxa ranging from the micrometer to the centimetre scales. The same hormone signalling pathways seems to be activated by very different kinds of soil organisms such as bacteria, nematodes, collembola and even earthworms, with common consequences on plant growth, development and defence. Plant hormonal homeostasis appears to be the corner stone to understand and predict the issue of the multiple interactions that plants entertain with the community of soil organisms.


Via Jean-Michel Ané, Mary Williams, Gilson Dahmer
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Plant root exudates mediate neighbour recognition and trigger complex behavioural changes

Plant root exudates mediate neighbour recognition and trigger complex behavioural changes | soil science | Scoop.it

Some plant species are able to distinguish between neighbours of different genetic identity and attempt to pre-empt resources through root proliferation in the presence of unrelated competitors, but avoid competition with kin. However, studies on neighbour recognition have met with some scepticism because the mechanisms by which plants identify their neighbours have remained unclear.In order to test whether root exudates could mediate neighbour recognition in plants, we performed a glasshouse experiment in which plants of Deschampsia caespitosa were subjected to root exudates collected from potential neighbours of different genetic identities, including siblings and individuals belonging to the same or a different population or species.Our results show that root exudates can carry specific information about the genetic relatedness, population origin and species identity of neighbours, and trigger different responses at the whole root system level and at the level of individual roots in direct contact with locally applied exudates. Increased root density was mainly achieved through changes in morphology rather than biomass allocation, suggesting that plants are able to limit the energetic cost of selfish behaviour.This study reveals a new level of complexity in the ability of plants to interpret and react to their surroundings.

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Polypeptide signaling molecules in plant development

Polypeptide signaling molecules in plant development | soil science | Scoop.it
Highlights



Multiple CLE peptides signal through the multi-functional CLV1 receptor kinase.


Root meristem development is regulated by CLE and GLV/RGF polypeptide signals.


Lateral root emergence relies on auxin-induced, IDA-dependent signaling.


Root protoxylem differentiation depends on a CLE45–BAM3 signaling module.


ESF1 and CLE8 polypeptides non-cell autonomously control early embryogenesis.

Intercellular communication mediated by small signaling molecules is a key mechanism for coordinating plant growth and development. In the past few years, polypeptide signals have been shown to play prominent roles in processes as diverse as shoot and root meristem maintenance, vascular differentiation, lateral root emergence, and seed formation. Signaling components such as CLV1 and the IDA-HAE/HSL2 signaling module have been discovered to regulate distinct developmental processes in different tissues. Recent studies have also uncovered novel polypeptide–receptor interactions, intracellular components and downstream target genes, adding complexity to our picture of polypeptide signaling networks. Finally, new families of plant polypeptides, such as the GLV/RGF/CLEL and ESF factors, are being identified, the functions of which we are only beginning to understand.
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Comparison of the Rhizosphere Bacterial Communities of Zigongdongdou Soybean and a High-Methionine Transgenic Line of This Cultivar

Comparison of the Rhizosphere Bacterial Communities of Zigongdongdou Soybean and a High-Methionine Transgenic Line of This Cultivar | soil science | Scoop.it

Previous studies have shown that methionine from root exudates affects the rhizosphere bacterial population involved in soil nitrogen fixation. A transgenic line of Zigongdongdou soybean cultivar (ZD91) that expresses Arabidopsis cystathionine γ-synthase resulting in an increased methionine production was examined for its influence to the rhizosphere bacterial population. Using 16S rRNA gene-based pyrosequencing analysis of the V4 region and DNA extracted from bacterial consortia collected from the rhizosphere of soybean plants grown in an agricultural field at the pod-setting stage, we characterized the populational structure of the bacterial community involved. In total, 87,267 sequences (approximately 10,908 per sample) were analyzed. We found that Acidobacteria, Proteobacteria, Bacteroidetes, Actinobacteria, Chloroflexi, Planctomycetes, Gemmatimonadetes, Firmicutes, and Verrucomicrobia constitute the dominant taxonomic groups in either the ZD91 transgenic line or parental cultivar ZD, and that there was no statistically significant difference in the rhizosphere bacterial community structure between the two cultivars.

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Gilson Dahmer's curator insight, August 5, 2014 2:32 PM

Interessantíssimo!

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Using root form to improve our understanding of root function -

Using root form to improve our understanding of root function - | soil science | Scoop.it

It has been said – and even written – that the ‘fine roots of perennial plants are a royal pain to study’ (Pregitzer, 2002). This is because the complex branching architecture of ephemeral roots leads to changes in root form and function across sub-millimeter scales (Fig. 1). While painful to consider, the variation in traits from short-lived, absorptive root tips to more proximal, transportive roots, may be our best hope of quantifying and understanding the functional role of living roots throughout the soil profile. Further, inherent variation in root functional traits across plant species may allow us to scale root function from the rhizosphere to the biosphere in order to understand global biogeochemical cycling under current and future climatic conditions. This issue of New Phytologist contains two papers that approach the linkages between root form and function from different, but complementary, directions. Kong et al. (pp. 863–872) take a broad geographic approach, describing patterns of trait variation across the distal root tips of 96 subtropical and tropical tree species in southern China, while Smith et al. (pp. 851–862) worked at the scale of a single site to investigate the relationships among root traits and root decomposition rates of graminoid species across a gradient of soil moisture in grazed ecosystems in central Scotland.

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