Trade-offs between growth, storage and defense in plants under carbon limitation

The fate of C, i.e. C allocation, plays a fundamental role in growth, survival and reproduction of organisms, particularly sessile organisms like plants that cannot escape harsh environmental conditions thus have to deal with stress with locally limited resources. Rapidly changing climate in recent years, for example drought and heat-enhanced insect outbreaks, and elevated atmospheric CO2 concentrations as well as rising air temperature, have sparked our interest in understanding, among others, how plants allocate C into growth, nonstructural carbohydrates (NSC) storage, secondary metabolites (SM) and biogenic volatile organic compounds (BVOC). By reducing CO2 thus forcing plants into a severe resource trade-off, I provide empirical evidence for the allocation priorities and the underlying control mechanisms. ..

Plants with arbuscular mycorrhizal fungi efficiently acquire Nitrogen from substrate additions by shaping the decomposer community composition and their net plant carbon demand

Acknowledgements SC received funding from long term DAAD scholarship to carry out the research. ML is funded by the German Research Foundation (DFG; FOR 456, FOR 1451 – “The Jena Experiment”) and by the “Zwillenberg-Tietz Stiftung”. We acknowledge help from Agnes Fastnacht with greenhouse resources and monitoring of the experiment. Special thanks to Karl Kübler for construction and deployment of the pulse labelling setup in the greenhouse. We acknowledge Heike Geilmann and Steffen Ruehlow for help with stable isotope measurements, and Maria Foerster for helping with fatty acid analysis. We also thank Erika Kothe, Ruchira Mukherji, Elisa Catao and Huei Ying Gan for helpful comments and discussions and Simon Benk for proof reading the MS. Funding Open Access funding enabled and organized by Projekt DEAL.Peer reviewedPublisher PD

Tree defence and bark beetles in a drying world: carbon partitioning, functioning and modelling.

Drought has promoted large-scale, insect-induced tree mortality in recent years, with severe consequences for ecosystem function, atmospheric processes, sustainable resources and global biogeochemical cycles. However, the physiological linkages among drought, tree defences, and insect outbreaks are still uncertain, hindering our ability to accurately predict tree mortality under on-going climate change. Here we propose an interdisciplinary research agenda for addressing these crucial knowledge gaps. Our framework includes field manipulations, laboratory experiments, and modelling of insect and vegetation dynamics, and focuses on how drought affects interactions between conifer trees and bark beetles. We build upon existing theory and examine several key assumptions: (1) there is a trade-off in tree carbon investment between primary and secondary metabolites (e.g. growth vs defence); (2) secondary metabolites are one of the main component of tree defence against bark beetles and associated microbes; and (3) implementing conifer-bark beetle interactions in current models improves predictions of forest disturbance in a changing climate. Our framework provides guidance for addressing a major shortcoming in current implementations of large-scale vegetation models, the under-representation of insect-induced tree mortality

Plants with arbuscular mycorrhizal fungi efficiently acquire nitrogen from substrate additions by shaping the decomposer community composition and their net plant carbon demand

Aims: We investigated the role of plants and their plant-derived carbon in shaping the microbial community that decomposes substrates and traced the return of nutrients from decomposition back to plant shoots in order to understand the importance of plants for ecosystem element cycling. Methods: We performed a greenhouse experiment having plant communities with and without arbuscular mycorrhizal fungi (AMF) and ingrowth cores that held different 15N labeled substrates. We determined the microbial community structure using molecular sequencing and the net assimilation of plant carbon into soil microorganisms using a 13CO2 pulse and 13C measurements of microbial biomarkers. We determined the return of nitrogen back to the shoots using the 15N signal, which was provided from the decomposition of the substrate added to the ingrowth cores. Results: We observed that the microbial community composition in the ingrowth cores and their net 13C assimilation depended on the presence of AMF and the added substrate. Both plant communities had similar 15N uptake into their shoots, but the net N uptake cost was significantly lower in presence of AMF. In the presence of AMF also lower net N uptake cost was observed for the decomposition of plant-derived and microorganism-derived substrates compared to inorganic nitrogen suggesting that AMF actively controls the decomposer comunity and their carbon demand. Conclusion: Our results identify for the first time a functional overlap of soil microorganisms as identical substrate is decomposed by different microorganisms suggesting functional redundancy of microbial communities. In consequence a better understanding of ecosystem element cycling can only be achieved when the whole plant-microorganism-organic matter-soil continuum is investigated

Eyes on the future – evidence for trade‐offs between growth, storage and defense in Norway spruce

Carbon (C) allocation plays a central role in tree responses to environmental changes. Yet, fundamental questions remain about how trees allocate C to different sinks, for example, growth vs storage and defense. In order to elucidate allocation priorities, we manipulated the whole‐tree C balance by modifying atmospheric CO2 concentrations [CO2] to create two distinct gradients of declining C availability, and compared how C was allocated among fluxes (respiration and volatile monoterpenes) and biomass C pools (total biomass, nonstructural carbohydrates (NSC) and secondary metabolites (SM)) in well‐watered Norway spruce (Picea abies) saplings. Continuous isotope labelling was used to trace the fate of newly‐assimilated C. Reducing [CO2] to 120 ppm caused an aboveground C compensation point (i.e. net C balance was zero) and resulted in decreases in growth and respiration. By contrast, soluble sugars and SM remained relatively constant in aboveground young organs and were partially maintained with a constant allocation of newly‐assimilated C, even at expense of root death from C exhaustion. We conclude that spruce trees have a conservative allocation strategy under source limitation: growth and respiration can be downregulated to maintain ‘operational’ concentrations of NSC while investing newly‐assimilated C into future survival by producing SM.Supplementary material: Fig. S1 Concentrations of soluble sugars, starch and NSC (soluble sugars + starch) expressed as percentage of control (400 ppm [CO2]) at the whole‐tree level. Fig. S2 Concentrations of soluble sugars, starch and NSC (soluble sugars + starch) at the whole‐tree level. Fig. S3 Concentrations of phenolic compounds, monoterpenes and total secondary metabolites expressed as percentage of control (400 ppm [CO2]) at the whole‐tree level. Fig. S4 Concentrations of phenolic compounds, monoterpenes and total secondary metabolites (phenolic compounds + monoterpenes) at the whole‐tree level. Fig. S5 δ13C (‰) of bulk tissue, water soluble C and phenolic compounds at the whole‐tree level. Methods S1 TD‐GC‐MS conditions for BVOC analysis. Table S1 Internal standards, weight‐based response factors and methods used for the measurements of secondary metabolites. Table S2 A rough estimation of allocation of newly‐assimilated carbon.JH was funded by the Chinese Scholarship Council and Max Planck Institute for Biogeochemistry, and acknowledges support from the International Max Planck Research School for Global Biogeochemical Cycles.http://www.newphytologist.com2020-04-01hj2019Forestry and Agricultural Biotechnology Institute (FABI)Zoology and Entomolog

Storage of carbon reserves in spruce trees is prioritized over growth in the face of carbon limitation

Climate change is expected to pose a global threat to forest health by intensifying extreme events like drought and insect attacks. Carbon allocation is a fundamental process that determines the adaptive responses of long-lived late-maturing organisms like trees to such stresses. However, our mechanistic understanding of how trees coordinate and set allocation priorities among different sinks (e.g., growth and storage) under severe source limitation remains limited. Using flux measurements, isotopic tracing, targeted metabolomics, and transcriptomics, we investigated how limitation of source supply influences sink activity, particularly growth and carbon storage, and their relative regulation in Norway spruce (Picea abies) clones. During photosynthetic deprivation, absolute rates of respiration, growth, and allocation to storage all decline. When trees approach neutral carbon balance, i.e., daytime net carbon gain equals nighttime carbon loss, genes encoding major enzymes of metabolic pathways remain relatively unaffected. However, under negative carbon balance, photosynthesis and growth are down-regulated while sucrose and starch biosynthesis pathways are up-regulated, indicating that trees prioritize carbon allocation to storage over growth. Moreover, trees under negative carbon balance actively increase the turnover rate of starch, lipids, and amino acids, most likely to support respiration and mitigate stress. Our study provides molecular evidence that trees faced with severe photosynthetic limitation strategically regulate storage allocation and consumption at the expense of growth. Understanding such allocation strategies is crucial for predicting how trees may respond to extreme events involving steep declines in photosynthesis, like severe drought, or defoliation by heat waves, late frost, or insect attack.DATA AVAILABITY : All study data are included in the article and/or supporting information. Transcriptome data have been deposited in the NCBI database under BioProject accession no. PRJNA751264.Max Planck Society.https://www.pnas.orghj2022BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements