Nutrient Acquisition Strategies Research Articles

Dynamics of plant nutrient requirements and acquisition strategies after afforestation: A study on the Loess Plateau, China

Plant nutrient requirements and acquisition strategies are critical to understand the net primary productivity and community stability in terrestrial ecosystems. However, the current knowledge regarding this subject is limited, especially in the case of afforestation. Therefore, we selected four Robinia pseudoacacia (RP) forests (15-, 21-, 31-, and 46-year-old forests) in the Loess Plateau, and analyzed the nutrients in the plant organs, litter, and soil, along with the extracellular enzyme activities (EEAs), microbial biomass, and mineralization rate. In addition, the biomass of RP was determined using an allometric growth model. The results showed that during afforestation, the nitrogen and phosphorus requirement of RP increased significantly, from 3.97 to 18.14 g·m−2·year−1 and 0.17 to 0.71 g·m−2·year−1, respectively, while the nutrient resorption efficiency and the contributions of nutrient resorption to the total nutrient requirements significantly decreased. Meanwhile, the ratio of nitrogen to phosphorus resorption efficiency (NRE:PRE) significantly increased with afforestation, but were less than 1 which may indicate the phosphorus limitation of RP decreased. In addition, the vector angle significantly increased form 44.80° to 49.51° after afforestation, which may indicate the phosphorus limitation of soil microorganisms increased. Meanwhile, the vector angle was significantly positive with phosphorus mineralization rate and NRE:PRE, which may show that soil microorganisms activity alleviate the phosphorus limitation of plants. Collectively, our study contributes to a better understanding of nutrient cycling above and below the ground.

Comparison of root morphology and rhizosphere microbial communities form moso-bamboo in different forest types.

Moso-bamboo (Phyllostachys edulis), with the favor of human disturbance, rapidly invades adjacent forests to form monocultures in East Asia. Moso-bamboo not only intrudes the broadleaf forests but also the coniferous, and it could impact by above- and below-ground pathways. However, it still remains unclear whether the below-ground performance of moso-bamboo differs from broadleaf to coniferous forests, especially those differing in competitive and nutrient acquisition strategies. In this study, we investigated three types of forest stands in Guangdong, China, including a bamboo monoculture, a coniferous forest, and a broadleaf forest. We found that moso-bamboo may suffer stronger soil P limitation (soil N/P = 18.16) and may be infected by more AMF in coniferous than broadleaf forests (soil N/P = 16.17). Based on our PLS-path model analysis, soil P resource may be the key to differ moso-bamboo root morphology and rhizosphere microbe in different forests: in broadleaf forests with weaker soil P limitation, may be realized through increasing specific root length and specific surface area, whereas in coniferous forests with stronger soil, P limitation may be realized through combining more AMF. Our study highlights the importance of underground mechanisms about moso-bamboo expansion in different forest communities.

Contrasted root trait responses between saplings of an arbuscular and an ectomycorrhizal tree species in open field compared to forest conditions

Abstract Plant nutrient acquisition strategies range along a spectrum from autonomous foraging to investment in cooperative foraging through mycorrhizal associations. However, in temperate ecosystems, many plant species encounter contrasted levels of symbiont availability in open fields versus closed forests. Little is known about how fungal partner availability may be associated with intraspecific variation in other root foraging traits in natural settings. Here, we addressed this issue by sampling saplings from two tree species: the arbuscular mycorrhizal (AM) Acer rubrum and the ectomycorrhizal (ECM) Quercus rubra from open fields (AM dominated) and adjacent forest plots (ECM dominated). For each species and environment, we measured morphological, architectural and symbiotic root traits. For the open field, Quercus had greater specific root length (SRL) while Acer had higher AM colonization and root diameter. In the closed forest, the opposite pattern was observed, namely Quercus had higher ECM colonization and Acer greater SRL. Both species showed evidence of a shift towards autonomous root foraging in the habitat with low expected symbiont abundance (open field for Quercus and forest for Acer). Although the confounding effects of site abiotic properties could not be strictly controlled in this study, these results suggest that plants might adjust root foraging traits according to local habitat conditions. Synthesis: Our results shed new light on the intraspecific variation in plant position along the so‐called ‘collaboration gradient’, and suggest that mycorrhizal symbiont availability, along with other factors such as competition and site properties, may contribute to this variation.

Nitrogen addition influences fine root growth and mycorrhizal symbiosis formation in trees with contrasting root morphology

Nitrogen (N) addition influences fine root growth and mycorrhizal symbiosis formation, the two dominant strategies for tree nutrient acquisition. Arbuscular mycorrhizae (AM) and ectomycorrhizae (ECM) are the two dominant types of mycorrhizal fungi that form symbioses with the roots of most trees. To reveal the divergent adaptive mechanisms and nutrient acquisition strategies of AM and ECM trees under N addition, we investigated the growth and nutrient acquisition of three dominant tree species in a subtropical forest with contrasting fine roots and mycorrhizal fungi symbioses. Castanopsis hystrix with thin fine roots forms associations with ECM. Michelia macclurei and Phoebe bournei with relatively thick fine roots form associations with AM. N addition facilitates the growth of AM trees more obvious than that of the EMC tree. Acid phosphatase activity was increased to overcome N addition-induced P deficiency. The increase in acid phosphatase activity in the rhizosphere of the ECM tree was greater than in AM trees. N addition decreased fine root length and mycorrhizal fungi colonization in all three tree species. The responses of fine roots and mycorrhizal fungi to N addition were species-specific: fine roots were more sensitive than mycorrhizal fungi for C. hystrix and P. bournei, while the opposite pattern (sensitivity of mycorrhiza > roots) was observed for M. macclurei. The divergent sensitivity of the two dominant nutrient acquisition strategies among tree species may facilitate ecological niche partitioning and inter-specific coexistence under limited nutrient availability.

Divergent response of soil microbes to environmental stress change under different plant communities in the Loess Plateau

Soil microorganisms play a crucial role in the proper functioning and stability of grassland ecosystems, and are influenced by the nutrient acquisition strategies of their host plants. The Loess Plateau in China, is known for its severe soil erosion and distinctive loess deposits, with soil nutrient levels declining from southeast to northwest. However, little is known about the relative effects of different host plants on soil microbial communities under different environmental stress in the Loess Plateau. We investigated the microbial community within soil profiles (0–100 cm) under two types of grasses community (Agropyron cristatum and Stipa spp.) with different drought tolerances, which are widely distributed in three different climate regions of the Loess Plateau. The diversity, composition, community assembly, and predicted functions of the bacterial and fungal community were evaluated. We discovered that the climate-plant-soil microbe interactions were the most significant factor affecting the community composition of bacteria and fungi on the regional scale. In addition, the effects of edaphic factors (e.g., soil organic carbon [SOC], total nitrogen [TN], and total phosphorus [TP]) on the soil bacterial and fungal communities increased from the warm-temperate to the desert steppe environment. Furthermore, the microbial community and assembly processes were driven by TP content of Agropyron grass, which is more resistant to environmental stress, while the soil of Stipa grass was driven by SOC. This may have occurred because the soil microbes in the Agropyron grassland had a stronger ability to utilize refractory organic matter thus reducing dependence on SOC, compared to soil microbes in the Stipa grassland. Collectively, our results show that the soil microbes recruited by the different plant communities responded differently in microbial composition, assembly, and functions to adapt the environmental stress change.

Effects of atrazine on microbial metabolic limitations in black soils: Evidence from enzyme stoichiometry

Long-term input of agricultural chemicals such as pesticides into the soil can increase soil pollution, thereby affecting the productivity and quality of black soil. Triazine herbicide atrazine has been shown to have long-lasting residual effects in black soil. The atrazine residues affected soil biochemical properties, further leading to microbial metabolism restriction. It is necessary to explore the strategies to mitigate the limitations on microbial metabolism in atrazine-contaminated soils. Here, we evaluated the effect of the atrazine on microbial nutrient acquisition strategies as indicated by extracellular enzyme stoichiometry (EES) in four black soils. Atrazine degradation in soil followed the first-order kinetics model across various concentrations ranging from 10 to 100 mg kg−1. We found that the atrazine was negatively correlated with the EES for C-, N-, and P-acquisition. Vector lengths and angles decreased and increased significantly with an increase of atrazine concentration in tested black soils except for Lishu soils. Moreover, the vector angles were >45° for tested four black soils, indicating that atrazine residue had the greatest P-limitation on soil microorganisms. Interestingly, microbial C- and P-limitations with different atrazine concentrations showed a strong linear relationship, especially in Qiqihar and Nongan soils. Atrazine treatment significantly negatively affected microbial metabolic limitation. Soil properties and EES interaction explained up to 88.2% for microbial C-/P-limitation. In conclusion, this study confirms the EES as a useful method in evaluating the effects of pesticides on microbial metabolic limitations.

Relationships between carboxylate-based nutrient-acquisition strategies, phosphorus-nutritional status and rare earth element accumulation in plants

Relationships between carboxylate-based nutrient-acquisition strategies, phosphorus-nutritional status and rare earth element accumulation in plants

Restoration on magnetite mine waste substrates using Western Australian native plants only marginally benefited from a commercial inoculant

Post-mining landscapes often lack self-sustaining plant communities and functional belowground microbial communities. Inappropriate management of soil can hinder ecological restoration of mine sites. However, the potential role of microbial inoculants and plant nutrient-acquisition strategies in improving mined substrates and facilitating mine-site restoration remains relatively unexplored. An eight-month glasshouse experiment was conducted to test: (1) whether a commercially-available microbial inoculant was effective in restoring biological properties of mined substrates, and (2) the effect of plant nutrient-acquisition strategies on improving the chemical properties of mined substrates for the growth of native plants. There was no significant improvement in plant growth by adding a commercially-sourced microbial inoculant. Soil microbial biomass carbon and phosphorus increased significantly after plant growth (main effect of species * substrates * inoculation interaction). The non-mycorrhizal disturbance-specialist plant species Maireana georgei was effective in improving hostile conditions of the mine waste. Our results highlight that re-vegetating stockpiled topsoil using local keystone species is a desirable practice that can improve soil biological properties and benefit mine-site restoration. Commercially-available agricultural-based microbial inoculants may not be compatible for mine-site restoration using native plants, but future research using indigenous soil microbes is warranted.

Plant-soil feedback regulates the trade-off between phosphorus acquisition pathways in Pinus elliottii.

Plant-soil feedback (PSF) is conventionally characterized by plant biomass growth, yet it remains unclear how PSF affects plant nutrient acquisition strategies (e.g., nutrient absorption and nutrient resorption) associated with plant growth, particularly under changing soil environments. A greenhouse experiment was performed with seedlings of Pinus elliottii Englem and conditioned soils of monoculture plantations (P. elliottii and Cunninghamia lanceolata Hook). Soil sterilization was designed to test plant phosphorus (P) acquisition strategy with and without native soil fungal communities. Soils from P. elliottii and C. lanceolata plantations were used to explore the specific soil legacy effects on two different P acquisition pathways (absorption and resorption). Phosphorus addition was also applied to examine the separate and combined effects of soil abiotic factors and soil fungal factors on P acquisition pathways. Due to diminished mycorrhizal symbiosis, PSF prompted plants to increasingly rely on P resorption under soil sterilization. In contrast, P absorption was employed preferentially in the heterospecific soil, where species-specific pathogenic fungi could not affect P absorption. Higher soil P availability diluted the effects of soil fungal factors on the trade-off between the two P acquisition pathways in terms of the absolute PSF. Moreover, P addition plays a limited role in terms of the relative PSF and does not affect the direction and strength of relative PSF. Our results reveal the role of PSF in regulating plant P acquisition pathways and highlight the interaction between mycorrhizal and pathogenic fungi as the underlying mechanism of PSF.

Temperature drives the coordination between above‐ground nutrient conservation and below‐ground nutrient acquisition in alpine coniferous forests

Abstract Above‐ground nutrient conservation via resorption processes and below‐ground nutrient acquisition from soils are two important mechanisms for plants to maintain nutrition and ecosystem functions. However, the mechanism by which plants coordinate these two nutrient strategies, especially for ectomycorrhizal (ECM)‐dominated conifers in alpine forests, remains unclear. We investigated the relationships between above‐ground nutrient conservation and below‐ground nutrient acquisition and their environmental drivers by measuring leaf nutrient (i.e. nitrogen [N] and phosphorous [P]) resorption efficiency, resource foraging‐ and uptake‐related root morphological (root diameter [RD], specific root length [SRL]/area [SRA]) and physiological (root tissue density [RTD], root N and P concentration) traits, mycorrhizal colonization rate (MCR), rhizosphere effect on soil N and P cycling, and environmental factors of 40 ECM coniferous populations on the eastern Tibetan Plateau, China. Our results showed that with increasing leaf nutrient (N and P) resorption efficiency, conifers shifted from depending on the ‘outsourcing’ strategy by mycorrhizal fungi (high MCR) to relying on the ‘do‐it‐yourself’ strategy of root mining (high rhizosphere effect on N‐ and P‐mining‐related enzyme activities) rather than on root foraging (high SRL and SRA) and preferred more conservative roots (high RTD and low root N and P concentrations). Temperature was the main factor driving a negative relationship of ECM fungi foraging, root uptake and a positive relationship of root mining with leaf nutrient resorption, while precipitation resulted in a decoupled relationship between root foraging and leaf nutrient resorption. Our findings demonstrate temperature‐driven and diverse collaborations (e.g. trade‐off or synergy) between below‐ground nutrient acquisition and above‐ground nutrient conservation strategies in alpine ECM conifers and highlight that the preference for below‐ground nutrient acquisition strategies could influence the above‐ground nutrient utilization strategy. This is insightful for a holistic understanding of the adaptation and responses of alpine forests to climatic change. Read the free Plain Language Summary for this article on the Journal blog.

Soil water conditions together with plant nitrogen acquisition strategies control vegetation dynamics in semi-arid wetlands undergoing land management changes

Land management changes can significantly alter wetland soil environment, vegetation, and their interactions. Although the relationships between plant communities and environmental factors have been widely studied, the intrinsic driving mechanisms of vegetation dynamics are poorly understood because nutrient acquisition strategies play an important role in plant community assembly. This study compared the plant community characteristics of wetlands under different land management practices in the semi-arid western Songnen Plain, Northeast China, and investigated soil properties and plant community nutrient contents. Results showed compared with those in natural wetlands, the values of growth characteristics of plant communities were generally lower, whereas species diversity was higher in grazed or mowed wetlands. Furthermore, soil carbon (C), nitrogen (N), phosphorus (P) contents, their stoichiometric ratios, and soil water content were lower, and N contents in leaves and stems, soil bulk density, and pH were higher compared with those in natural wetlands. The plant community characteristics were significantly correlated with soil properties and plant nutrient contents. A redundancy analysis showed that soil water content, bulk density, and organic carbon, accounted for 59.3%, 15.6%, and 2.9%, respectively, the N in leaves, stems, and roots accounted for 62.8%, and the P in leaves and roots accounted for 12.2% of the variation in the plant community. Variation partitioning analysis further demonstrated that soil properties, plant nutrient contents, and their interactions explained 19.1 %, 11.8%, and 59.4% of the variation in the plant community, respectively. Therefore, the wetland vegetation dynamics are combinedly controlled by soil properties (especially soil water conditions) and plant nutrient acquisition strategies (especially plant nitrogen acquisition) under different land management practices. This study provides the theoretical basis for maintaining the stability of wetland ecosystems by designing plant resources-related managements in semi-arid regions.

Rhizosphere engineering for sustainable crop production: entropy-based insights.

There is a growing interest in exploring interactions at root-soil interface in natural and agricultural ecosystems, but an entropy-based understanding of these dynamic rhizosphere processes is lacking. We have developed a new conceptual model of rhizosphere regulation by localized nutrient supply using thermodynamic entropy. Increased nutrient-use efficiency is achieved by rhizosphere management based on self-organization and minimized entropy via equilibrium attractors comprising (i) optimized root strategies for nutrient acquisition and (ii) improved information exchange related to root-soil-microbe interactions. The cascading effects through different hierarchical levels amplify the underlying processes in plant-soil system. We propose a strategy for manipulating rhizosphere dynamics and improving nutrient-use efficiency by localized nutrient supply with minimization of entropy to underpin sustainable food/feed/fiber production.

Plant domestication shapes rhizosphere microbiome assembly and metabolic functions

BackgroundThe rhizosphere microbiome, which is shaped by host genotypes, root exudates, and plant domestication, is crucial for sustaining agricultural plant growth. Despite its importance, how plant domestication builds up specific rhizosphere microbiomes and metabolic functions, as well as the importance of these affected rhizobiomes and relevant root exudates in maintaining plant growth, is not well understood. Here, we firstly investigated the rhizosphere bacterial and fungal communities of domestication and wild accessions of tetraploid wheat using amplicon sequencing (16S and ITS) after 9 years of domestication process at the main production sites in China. We then explored the ecological roles of root exudation in shaping rhizosphere microbiome functions by integrating metagenomics and metabolic genomics approaches. Furthermore, we established evident linkages between root morphology traits and keystone taxa based on microbial culture and plant inoculation experiments.ResultsOur results suggested that plant rhizosphere microbiomes were co-shaped by both host genotypes and domestication status. The wheat genomes contributed more variation in the microbial diversity and composition of rhizosphere bacterial communities than fungal communities, whereas plant domestication status exerted much stronger influences on the fungal communities. In terms of microbial interkingdom association networks, domestication destabilized microbial network and depleted the abundance of keystone fungal taxa. Moreover, we found that domestication shifted the rhizosphere microbiome from slow growing and fungi dominated to fast growing and bacteria dominated, thereby resulting in a shift from fungi-dominated membership with enrichment of carbon fixation genes to bacteria-dominated membership with enrichment of carbon degradation genes. Metagenomics analyses further indicated that wild cultivars of wheat possess higher microbial function diversity than domesticated cultivars. Notably, we found that wild cultivar is able to harness rhizosphere microorganism carrying N transformation (i.e., nitrification, denitrification) and P mineralization pathway, whereas rhizobiomes carrying inorganic N fixation, organic N ammonification, and inorganic P solubilization genes are recruited by the releasing of root exudates from domesticated wheat. More importantly, our metabolite-wide association study indicated that the contrasting functional roles of root exudates and the harnessed keystone microbial taxa with different nutrient acquisition strategies jointly determined the aboveground plant phenotypes. Furthermore, we observed that although domesticated and wild wheats recruited distinct microbial taxa and relevant functions, domestication-induced recruitment of keystone taxa led to a consistent growth regulation of root regardless of wheat domestication status.ConclusionsOur results indicate that plant domestication profoundly influences rhizosphere microbiome assembly and metabolic functions and provide evidence that host plants are able to harness a differentiated ecological role of root-associated keystone microbiomes through the release of root exudates to sustain belowground multi-nutrient cycles and plant growth. These findings provide valuable insights into the mechanisms underlying plant-microbiome interactions and how to harness the rhizosphere microbiome for crop improvement in sustainable agriculture.CBzZNC2FEDswGcHctbDosaVideo

Nitrogen and phosphorous dynamics with stand development of Pinus massoniana plantations in Southeast China.

Nutrient resorption is a key mechanism to conserve nutrients and overcome nutrient limitation in perennial plants. As an important afforested tree species in subtropical regions, Pinus massoniana grows well in nutrient-poor environments, however, the age-related pattern of nutrient acquisition strategy and the underlying mechanisms in P. massoniana plantations remain unclear. In this study, concentrations of nitrogen (N) and phosphorus (P) were measured in green and senesced needles, roots and soil samples collected from P. massoniana plantations with different stand ages (9-, 17-, 26-, 34- and 43-year-old) in south China. From these samples, nutrient resorption efficiency (RE) and stoichiometry were calculated. Needle PRE significantly decreased with stand age, while there was no clear pattern of NRE along the stand development. Green needle N:P in older stands was significantly lower than in younger ones. Senesced needle C:P and N:P significantly decreased with stand age. Root and soil available P concentrations were significantly higher in older stands than in younger ones, and PRE was negatively correlated with soil available P concentration. There was a shift from "conservative consumption" to "resource spending" P-use strategy, and P limitation decreased with stand development of P. massoniana plantations. The results provide information of changes in nutrients dynamics, which is relevant for the sustainable management of subtropical forest plantations.

Intercropping increases soil N-targeting enzyme activities: A meta-analysis

Intercropping rationally utilizes land resources and effectively increases soil biodiversity. The enzyme-mediated biological catabolism of soil organic and mineral components is a crucial step in controlling soil carbon and nutrient circulation and fixation in agroecosystems, and those enzymes involved in nitrogen (N) cycling are particularly important. However, when considering different crop combinations, the effects of intercropping on N-targeting enzyme activities remain uncertain. Given such incomplete knowledge of these belowground processes and interactions, we synthesized results for three kinds of N-targeting enzyme activities in response to intercropping based on 117 peer-reviewed papers, in which 454 observations were included. We found that intercropping significantly increased the activity of N-acetyl-glucosaminidase by 26.1%, protease by 10.2%, and urease by 22.2%. Our results suggest that the intercropping effect is mediated by responses of the soil microbes to the diversity of soil nutrients under different crop combinations. Soil N availability and crop competition for nutrients between plant crops mediate patterns of microbial nutrient acquisition strategies and secretion of N-targeting enzymes. Our comprehensive meta-analysis highlights the importance of intercropping for better soil quality and biodiversity and has implications for the role of intercropping in regulating soil carbon dynamics.

Fungi in ant-plant interactions: a key to enhancing plant nutrient-acquisition strategies.

This article is a Commentary on Gegenbauer et al. (2023), 238: 2210–2223.

Rural mixed pond water irrigation affected microbial community and eco-enzymatic stoichiometry of soil profiles

The application of rural mixed pond water (RMW) for irrigation has become a relatively normal agricultural practice in China. However, it is not clear whether soil microbial activity and soil stored nutrients are influenced by RMW. In this study, soil samples were collected from a depth of 0–60 cm for determining their basic physicochemical properties, microbial biomass and soil enzyme activities, moreover, the eco-enzymatic stoichiometry ratio was determined to evaluate microbial nutrient requirements. Our results showed that, with the increase in the soil depth, dissolved organic carbon, available phosphorus, microbial contents, and extracellular enzyme activities declined. We observed an increment in the microbial biomass nitrogen (MBN; 1.44 fold) and microbial biomass carbon (MBC; 1.23 fold) from 0 to 10 cm after RMW irrigation. The latter was more stable below 40 cm of the soil layer independent of irrigation water. The increase in carrier length and angular carrier indicated that the microorganisms were limited by carbon (C) and phosphorus (P). The RMW irrigation significantly decreased the β-1,4-Nacetylglucosaminidase (NAG), the leucine aminopeptidase (LAP), and the phosphatase (AP). In addition, RMW irrigation increased the α-diversity of surface soil microorganisms but suppressed them in deeper soil profiles. The RDA analysis suggested that random NAG of exoenzymes had the greatest relative contribution to microbial diversity, with bacteria and fungi accounting for 27.1 % and 25.1 %, respectively. This study showed that RMW irrigation led to changes the soil extracellular enzyme activities, resulting in alterations the enzyme stoichiometry ratios and microbial nutrient acquisition strategies.

Escherichia coli Leucine-Responsive Regulatory Protein Bridges DNA In Vivo and Tunably Dissociates in the Presence of Exogenous Leucine.

Feast-famine response proteins are a widely conserved class of global regulators in prokaryotes, the most highly studied of which is the Escherichia coli leucine-responsive regulatory protein (Lrp). Lrp senses the environmental nutrition status and subsequently regulates up to one-third of the genes in E. coli, either directly or indirectly. Lrp exists predominantly as octamers and hexadecamers (16mers), where leucine is believed to shift the equilibrium toward the octameric state. In this study, we analyzed the effects of three oligomerization state mutants of Lrp in terms of their ability to bind to DNA and regulate gene expression in response to exogenous leucine. We find that oligomerization beyond dimers is required for Lrp's regulatory activity and that, contrary to previous speculation, exogenous leucine modulates Lrp activity at its target promoters exclusively by inhibiting Lrp binding to DNA. We also show evidence that Lrp binding bridges DNA over length scales of multiple kilobases, revealing a new range of mechanisms for Lrp-mediated transcriptional regulation. IMPORTANCE Leucine-responsive regulatory protein (Lrp) is one of the most impactful regulators in E. coli and other bacteria. Lrp senses nutrient conditions and responds by controlling strategies for virulence, cellular motility, and nutrient acquisition. Despite its importance and being evolutionarily highly conserved across bacteria and archaea, several mysteries remain regarding Lrp, including how it actually responds to leucine to change its regulation of targets. Previous studies have led to the hypothesis that Lrp switches between two states, an octamer (8 Lrp molecules together) and a hexadecamer (16 Lrp molecules together), upon exposure to leucine; these are referred to as different oligomerization states. Here, we show that contrary to previous expectations, it is Lrp's propensity to bind DNA, rather than its oligomerization state, that is directly affected by leucine in the cell's environment. Our new understanding of Lrp activity will aid in identifying and disrupting pathways used by bacteria to cause disease.

Compartmentalisation: A strategy for optimising symbiosis and tradeoff management.

Plant root architecture is developmentally plastic in response to fluctuating nutrient levels in the soil. Part of this developmental plasticity is the formation of dedicated root cells and organs to host mutualistic symbionts. Structures like nitrogen-fixing nodules serve as alternative nutrient acquisition strategies during starvation conditions. Some root systems can also form myconodules-globular root structures that can host mycorrhizal fungi. The myconodule association is different from the wide-spread arbuscular mycorrhization. This range of symbiotic associations provides different degrees of compartmentalisation, from the cellular to organ scale, which allows the plant host to regulate the entry and extent of symbiotic interactions. In this review, we discuss the degrees of symbiont compartmentalisation by the plant host as a developmental strategy and speculate how spatial confinement mitigates risks associated with root symbiosis.

Complementary belowground strategies underlie species coexistence in an early successional forest.

Unravelling belowground strategies is critical for understanding species coexistence and successional dynamics; yet, our knowledge of nutrient acquisition strategies of forest species at different successional stages remains limited. We measured morphological (diameter, specific root length, and root tissue density), architectural (branching ratio), physiological (ammonium, nitrate, and glycine uptake rates) root traits, and mycorrhizal colonisation rates of eight coexisting woody species in an early successional plantation forest in subtropical China. By incorporating physiological uptake efficiency, we revealed a bi-dimensional root economics space comprising of an 'amount-efficiency' dimension represented by morphological and physiological traits, and a 'self-symbiosis' dimension dominated by architectural and mycorrhizal traits. The early pioneer species relied on root-fungal symbiosis, developing densely branched roots with high mycorrhizal colonisation rates for foraging mobile soil nitrate. The late pioneer species invested in roots themselves and allocated effort towards improving uptake efficiency of less-mobile ammonium. Within the root economics space, the covariation of axes with soil phosphorus availability also distinguished the strategy preference of the two successional groups. These results demonstrate the importance of incorporating physiological uptake efficiency into root economics space, and reveal a trade-off between expanding soil physical space exploration and improving physiological uptake efficiency for successional species coexistence in forests.