Adaptive strategies for nitrogen metabolism in phosphate deficient legume nodules

Valentine, Alex J.; Kleinert, Aleysia; Benedito, Vagner A.

doi:10.1016/j.plantsci.2016.12.010

Cited by 73 publications

(46 citation statements)

References 45 publications

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“…For example, within the first two years after fire, at least 1 kg ha −1 yr −1 of N can be fixed by N 2 -fixing plants such as Acacia species (Hingston et al 1982), and~10% of this fixed N can be transferred between plants based on interplant N transfer studies (He et al 2009). However, the ability to fix N 2 strongly depends on P availability, since N 2 fixation is a process requiring substantial amounts of P (Raven 2012;Valentine et al 2017;Vitousek et al 2002). A few years (>5) after fire, soil P becomes less available, and the abundance of N 2 -fixing plants declines (Fig.…”

Section: Nutrient Exchange-based Facilitationmentioning

confidence: 99%

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

et al. 2017

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Background Mycorrhizal strategies are very effective in enhancing plant acquisition of poorly-mobile nutrients, particularly phosphorus (P) from infertile soil. However, on very old and severely P-impoverished soils, a carboxylate-releasing and P-mobilising cluster-root strategy is more effective at acquiring this growthlimiting resource. Carboxylates are released during a period of only a few days from ephemeral cluster roots. Despite the cluster-root strategy being superior for P acquisition in such environments, these species coexist with a wide range of mycorrhizal species, raising questions about the mechanisms contributing to their coexistence. Scope We surmise that the coexistence of mycorrhizal and non-mycorrhizal strategies is primarily accounted for by a combination of belowground mechanisms, namely (i) facilitation of P acquisition by mycorrhizal plants from neighbouring cluster-rooted plants, and (ii) interactions between roots, pathogens and mycorrhizal fungi, which enhance the plants' defence against pathogens. Facilitation of nutrient acquisition by clusterrooted plants involves carboxylate exudation, making more P available for both themselves and their mycorrhizal neighbours. Belowground nutrient exchanges between carboxylate-exuding plants and mycorrhizal N 2 -fixing plants appear likely, but require further experimental testing to determine their nutritional and ecological relevance. Anatomical studies of roots of clusterrooted Proteaceae species show that they do not form a complete suberised exodermis. Conclusions The absence of an exodermis may well be important to rapidly release carboxylates, but likely lowers root structural defences against pathogens, Plant Soil (2018) particularly oomycetes. Conversely, roots of mycorrhizal plants may not be as effective at acquiring P when P availability is very low, but they are better defended against pathogens, and this superior defence likely involves mycorrhizal fungi. Taken together, we are beginning to understand how an exceptionally large number of plant species and P-acquisition strategies coexist on the most severely P-impoverished soils.

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Section: Nutrient Exchange-based Facilitationmentioning

confidence: 99%

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

et al. 2017

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“…Recent work appears to support the hypotheses that changes in soil nutrient availability or specific changes (e.g., soil organic P concentrations) may lead to a “switching” from AM to ECM or vice versa (Albornoz, Lambers, et al., ). Similarly, plants that host N‐fixing bacteria tend to down‐regulate atmospheric N‐fixation when growing in soils with high levels of N (Hellsten & Huss‐Danell, ) or in P‐deficient soils (Valentine, Kleinert, & Benedito, ). What remains unclear, however, is the relative importance of abiotic factors (e.g., soil nutrient availability) versus biotic factors (e.g., soil inoculum potential) in driving these dual or triple root symbioses.…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, plants that host N-fixing bacteria tend to down-regulate atmospheric N-fixation when growing in soils with high levels of N (Hellsten & Huss-Danell, 2000) or in P-deficient soils (Valentine, Kleinert, & Benedito, 2017). What remains unclear, however, is the relative importance of abiotic factors (e.g., soil nutrient availability) versus biotic factors (e.g., soil inoculum potential) in driving these dual or triple root symbioses.…”

Section: Introductionmentioning

confidence: 99%

Plasticity in root symbioses following shifts in soil nutrient availability during long‐term ecosystem development

Teste

Laliberté

2018

Journal of Ecology

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The vast majority of terrestrial plants form root symbioses with arbuscular mycorrhizal (AM) fungi to enhance nutrient (particularly phosphorus, P) acquisition. However, some plant species also form dual symbioses involving ectomycorrhizal (ECM) fungi, with a subset of those also forming triple symbioses also involving dinitrogen (N2)‐fixing bacteria. It has been suggested that these plants show plasticity in root symbioses to optimise nutrient acquisition depending on the type and strength of soil nutrient limitation (e.g., N vs. P), yet empirical evidence remains limited. Alternatively, the degree of investment or “preference” in particular root symbioses might simply reflect differences in inoculum potential among soils of contrasting nutrient availability, reflecting adaptations of root symbionts to different edaphic conditions. Here, we grew two co‐occurring plant species forming triple (AM/ECM/N2‐fixing; Acacia rostellifera) or dual (AM/ECM; Melaleuca systena) symbioses in soils of increasing age and contrasting nutrient availability from an Australian long‐term soil chronosequence to disentangle the relative importance of abiotic factors (e.g., soil nutrient availability and stoichiometry) and biotic factors (e.g., soil inoculum potential) in determining root colonisation patterns and functional outcomes of these multiple root symbioses. For both plant species, we found clear hump‐shaped plant growth patterns along the pedogenesis‐driven gradient in soil nutrient availability, with peak growth in intermediate‐aged soils, while high levels of mycorrhizal colonisation by the “preferred” root symbionts were maintained across all soils. We found large increases (540%) in foliar manganese concentrations with increasing soil age and declining P availability, suggesting that plants may be relying on the release of carboxylates to help acquire P in the most P‐impoverished soils. Finally, we found that soil abiotic properties, such as strong differences in soil nutrient availability, are generally more important than soil inoculum potential in explaining these shifts in our plant and root responses. Synthesis. Our study suggests that plants capable of forming multiple root symbioses show plasticity in their nutrient‐acquisition strategies following shifts in soil nutrients during long‐term ecosystem development, yet maintain a preference for certain root symbionts despite changes in soil microbial inoculum.

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“…P deficiencies in soil reduce nodule growth, nodule number, and nodule activity [89,90]. Plants mainly take up P in the form of orthophosphate.…”

Section: Available Soil Phosphorusmentioning

confidence: 99%

Challenges in Using Precision Agriculture to Optimize Symbiotic Nitrogen Fixation in Legumes: Progress, Limitations, and Future Improvements Needed in Diagnostic Testing

Thilakarathna

Raizada

2018

Agronomy

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Precision agriculture (PA) has been used for ≥25 years to optimize inputs, maximize profit, and minimize negative environmental impacts. Legumes play an important role in cropping systems, by associating with rhizobia microbes that convert plant-unavailable atmospheric nitrogen into usable nitrogen through symbiotic nitrogen fixation (SNF). However, there can be field-level spatial variability for SNF activity, as well as underlying soil factors that influence SNF (e.g., macro/micronutrients, pH, and rhizobia). There is a need for PA tools that can diagnose spatial variability in SNF activity, as well as the relevant environmental factors that influence SNF. Little information is available in the literature concerning the potential of PA to diagnose/optimize SNF. Here, we critically analyze SNF/soil diagnostic methods that hold promise as PA tools in the short-medium term. We also review the challenges facing additional diagnostics currently used for research, and describe the innovations needed to move them forward as PA tools. Our analysis suggests that the nitrogen difference method, isotope methods, and proximal and remote sensing techniques hold promise for diagnosing field-level variability in SNF. With respect to soil diagnostics, soil sensors and remote sensing techniques for nitrogen, phosphorus, pH, and salinity have short-medium term potential to optimize legume SNF under field conditions.

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Adaptive strategies for nitrogen metabolism in phosphate deficient legume nodules

Cited by 73 publications

References 45 publications

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems

Plasticity in root symbioses following shifts in soil nutrient availability during long‐term ecosystem development

Challenges in Using Precision Agriculture to Optimize Symbiotic Nitrogen Fixation in Legumes: Progress, Limitations, and Future Improvements Needed in Diagnostic Testing

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