Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Assessing the influences of ecological restoration on perceptions of cultural ecosystem services by residents of agricultural landscapes of western China
Dou, Yuehan ; Zhen, Lin ; Yu, Xiubo ; Bakker, Martha ; Carsjens, Gerrit Jan ; Xue, Zhichao - \ 2019
Science of the Total Environment 646 (2019). - ISSN 0048-9697 - p. 685 - 695.
Agricultural landscapes - Cultural ecosystem services - Ecological restoration - Household survey - Human perception

Landscape change caused by ecological restoration projects has both positive and negative influences on human livelihoods, yet surprisingly little research on the cultural consequences of ecological restoration in agricultural landscapes has taken place. Cultural consequences can be captured in the ecosystem services framework as cultural ecosystem services (CES). However, assessment and valuation of these services to support decision-making for this essential ecosystem is lacking. To help fill this gap, we assessed the opinions of Chinese rural communities about CES and the changes in their perception under the Grain for Green program (GFG), a nationwide program to relieve the pressure on ecosystems (soil erosion and land degradation) by converting cultivated land or barren land on steep slopes into grassland and forests. We used Guyuan City in China's Ningxia Hui Autonomous Region as a case study, using a workshop to identify the CES provided by the agricultural landscape, followed by semi-structured household interviews to quantify perceptions of these CES. We found that all eight CES types identified by the workshop were perceived by the rural communities. Reforestation changed their perceptions of CES directly due to land cover change and indirectly due to the resulting economic changes and migration of mostly young workers in search of better jobs. Cultivated land was perceived as more important than forest for CES provision. In addition, residential areas were perceived as providing significant CES because of local traditions that produce close and highly social neighborhood bonds in agricultural landscapes.

Distinct Roles of Non-Overlapping Surface Regions of the Coiled-Coil Domain in the Potato Immune Receptor Rx1
Slootweg, Erik J. ; Spiridon, Laurentiu N. ; Martin, Eliza C. ; Tameling, Wladimir I.L. ; Townsend, Philip D. ; Pomp, Rikus ; Roosien, Jan ; Drawska, Olga ; Sukarta, Octavina C.A. ; Schots, Arjen ; Borst, Jan Willem ; Joosten, Matthieu H.A.J. ; Bakker, Jaap ; Smant, Geert ; Cann, Martin J. ; Petrescu, Andrei-Jose ; Goverse, Aska - \ 2018
Plant Physiology 178 (2018)3. - ISSN 0032-0889 - p. 1310 - 1331.
The intracellular immune receptor Rx1 of potato (Solanum tuberosum), which confers effector-triggered immunity to Potato virus X, consists of a central nucleotide-binding domain (NB-ARC) flanked by a carboxyl-terminal leucine-rich repeat (LRR) domain and an amino-terminal coiled-coil (CC) domain. Rx1 activity is strictly regulated by interdomain interactions between the NB-ARC and LRR, but the contribution of the CC domain in regulating Rx1 activity or immune signaling is not fully understood. Therefore, we used a structure-informed approach to investigate the role of the CC domain in Rx1 functionality.
Targeted mutagenesis of CC surface residues revealed separate regions required for the intramolecular and intermolecular interaction of the CC with the NB-ARC-LRR and the cofactor Ran GTPase-activating protein2 (RanGAP2), respectively. None of the mutant Rx1 proteins was constitutively active, indicating that the CC does not contribute to the autoinhibition of Rx1 activity. Instead, the CC domain acted as a modulator of downstream responses involved in effector-triggered immunity. Systematic disruption of the hydrophobic interface between the four helices of the CC enabled the uncoupling of cell death and disease resistance responses. Moreover, a strong dominant negative effect on Rx1-mediated resistance and cell death was observed upon coexpression of the CC alone with full-length Rx1 protein, which depended on the RanGAP2-binding surface of the CC. Surprisingly, coexpression of the N-terminal half of the CC enhanced Rx1-mediated resistance, which further indicated that the CC functions as a scaffold for downstream components involved in the modulation of disease resistance or cell death signaling.
Mediator of tolerance to abiotic stress ERF6 regulates susceptibility of Arabidopsis to Meloidogyne incognita
Warmerdam, Sonja ; Sterken, Mark G. ; Schaik, Casper van; Oortwijn, Marian E.P. ; Lozano-Torres, Jose L. ; Bakker, Jaap ; Goverse, Aska ; Smant, Geert - \ 2018
Molecular Plant Pathology (2018). - ISSN 1464-6722
abiotic stress - Arabidopsis thaliana - ERF6 - genome-wide association mapping - Meloidogyne incognita - root-knot nematodes - transcription factor

Root-knot nematodes transform vascular host cells into permanent feeding structures to selectively withdraw their nutrients from host plants during the course of several weeks. The susceptibility of host plants to root-knot nematode infections is thought to be a complex trait involving many genetic loci. However, genome-wide association (GWA) analysis has so far revealed only four quantitative trait loci (QTLs) linked to the reproductive success of the root-knot nematode Meloidogyne incognita in Arabidopsis thaliana, which suggests that the genetic architecture underlying host susceptibility could be much simpler than previously thought. Here, we report that, by using a relaxed stringency approach in a GWA analysis, we could identify 15 additional loci linked to quantitative variation in the reproductive success of M. incognita in Arabidopsis. To test the robustness of our analysis, we functionally characterized six genes located in a QTL with the lowest acceptable statistical support and smallest effect size. This led us to identify ETHYLENE RESPONSE FACTOR 6 (ERF6) as a novel susceptibility gene for M. incognita in Arabidopsis. ERF6 functions as a transcriptional activator and suppressor of genes in response to various abiotic stresses independent of ethylene signalling. However, whole-transcriptome analysis of nematode-infected roots of the Arabidopsis erf6-1 knockout mutant line showed that allelic variation at this locus may regulate the conversion of aminocyclopropane-1-carboxylate (ACC) into ethylene by altering the expression of 1-aminocyclopropane-1-carboxylate oxidase 3 (ACO3). Our data further suggest that tolerance to abiotic stress mediated by ERF6 forms a novel layer of control in the susceptibility of Arabidopsis to M. incognita.

Verbetering brandveiligheid oudere veestallen
Bokma-Bakker, M.H. - \ 2018
Wageningen : Wageningen UR Livestock Research - 2 p.
Effects on participation and biodiversity of reforming the implementation of agri-environmental schemes in the Netherlands
Groeneveld, A.N. ; Peerlings, J.H.M. ; Bakker, M.M. ; Polman, N.B.P. ; Heijman, W.J.M. - \ 2018
Ecological Complexity (2018). - ISSN 1476-945X - 17 p.
Agri-environmental schemes - Biodiversity - Contracts - Mathematical programming

To prevent further biodiversity loss as a result of intensive agricultural practices, Agri-Environmental Schemes (AES) have been implemented on European farmland. Unfortunately these AES have not always been effective in terms of biodiversity and farmer participation. In an effort to improve the AES programme the Dutch government switched from an individual application system to a collective application system for AES payments in 2016. The goal of this paper is to analyse how the resilience of the land use system in terms of farmer participation in the AES and biodiversity is affected by the value farmers attach to biodiversity, and whether the shift from an individual to collective AES will affect the resilience of the land use system. We constructed a multi-objective mathematical programming model in which farmers maximise utility. Farmers are linked through their common effect on biodiversity. In the collective application system payments are only available when the biodiversity in the region is above a certain threshold. Simulation results show no difference in farmer participation and biodiversity between the individual application system and the collective application system when biodiversity weights are high. The land use system loses its resilience in terms farmer participation in the AES and biodiversity if we lower the biodiversity weights, this effect is stronger in the collective AES programme.

Utilization of bambara groundnut (Vigna subterranea (L.) Verdc.) for sustainable food and nutrition security in semi-arid regions of Zimbabwe
Mubaiwa, Juliet ; Fogliano, Vincenzo ; Chidewe, Cathrine ; Bakker, Evert Jan ; Linnemann, Anita R. - \ 2018
PLoS One 13 (2018)10. - ISSN 1932-6203

Bambara groundnut (Vigna subterranea (L.) Verdc.) is an indigenous legume crop, cultivated by subsistence farmers throughout sub-Saharan countries. Research findings indicate that the crop has great nutritional and agronomic potential, but it remains scientifically neglected. A baseline study was conducted in seven districts in semi-arid regions of rural Zimbabwe to gather knowledge on current production and utilization of bambara groundnut, assess its role in providing sustainable food and nutrition security for rural populations and determine priorities for follow-up research. Results revealed a variety of bambara groundnut processing techniques, which included boiling, soaking, roasting and milling across the surveyed districts. Reported constraints to processing and consumption included long cooking time, difficulties with milling and high firewood and water requirements. Fifty to eighty percent of respondents in all districts consumed bambara groundnut once or twice weekly from August to December. Preferred consumer attributes were taste, the satiating effect, nutritional benefits or a combination of these. Current, culturally acceptable processing techniques need improvement to support sustainable bambara groundnut processing while optimising nutrient bio-accessibility. Ultimately, community resilience to food and nutrition insecurity can be promoted by exchange of bambara groundnut processing knowledge amongst the production areas, involving the different stakeholders in the food supply chains.

Effecten van klimaatverandering
Bakker, Martha - \ 2018
Een toekomstvisie voor het Brabantse platteland
Bakker, Martha - \ 2018
Lezing in het Provinciehuis in Den Bosch voor beleidsmakers in natuurbeheer
Representation of decision-making in European agricultural agent-based models
Huber, Robert ; Bakker, Martha ; Balmann, Alfons ; Berger, Thomas ; Bithell, Mike ; Brown, Calum ; Grêt-Regamey, Adrienne ; Xiong, Hang ; Le, Quang Bao ; Mack, Gabriele ; Meyfroidt, Patrick ; Millington, James ; Müller, Birgit ; Polhill, J.G. ; Sun, Zhanli ; Seidl, Roman ; Troost, Christian ; Finger, Robert - \ 2018
Agricultural Systems 167 (2018). - ISSN 0308-521X - p. 143 - 160.

The use of agent-based modelling approaches in ex-post and ex-ante evaluations of agricultural policies has been progressively increasing over the last few years. There are now a sufficient number of models that it is worth taking stock of the way these models have been developed. Here, we review 20 agricultural agent-based models (ABM) addressing heterogeneous decision-making processes in the context of European agriculture. The goals of this review were to i) develop a framework describing aspects of farmers’ decision-making that are relevant from a farm-systems perspective, ii) reveal the current state-of-the-art in representing farmers’ decision-making in the European agricultural sector, and iii) provide a critical reflection of underdeveloped research areas and on future opportunities in modelling decision-making. To compare different approaches in modelling farmers’ behaviour, we focused on the European agricultural sector, which presents a specific character with its family farms, its single market and the common agricultural policy (CAP). We identified several key properties of farmers’ decision-making: the multi-output nature of production; the importance of non-agricultural activities; heterogeneous household and family characteristics; and the need for concurrent short- and long-term decision-making. These properties were then used to define levels and types of decision-making mechanisms to structure a literature review. We find most models are sophisticated in the representation of farm exit and entry decisions, as well as the representation of long-term decisions and the consideration of farming styles or types using farm typologies. Considerably fewer attempts to model farmers’ emotions, values, learning, risk and uncertainty or social interactions occur in the different case studies. We conclude that there is considerable scope to improve diversity in representation of decision-making and the integration of social interactions in agricultural agent-based modelling approaches by combining existing modelling approaches and promoting model inter-comparisons. Thus, this review provides a valuable entry point for agent-based modellers, agricultural systems modellers and data driven social scientists for the re-use and sharing of model components, code and data. An intensified dialogue could fertilize more coordinated and purposeful combinations and comparisons of ABM and other modelling approaches as well as better reconciliation of empirical data and theoretical foundations, which ultimately are key to developing improved models of agricultural systems.

Exploring the effects of feedbacks on land system behaviour : A Complex Adaptive Systems approach
Chen, Yang - \ 2018
Wageningen University. Promotor(en): Arnold Bregt; Martha Bakker, co-promotor(en): Arend Ligtenberg. - Wageningen : Wageningen University - ISBN 9789463433334 - 174
Using root traits to understand temporal changes in biodiversity effects in grassland mixtures
Bakker, Lisette M. ; Mommer, Liesje ; Ruijven, Jasper van - \ 2018
Oikos (2018). - ISSN 0030-1299
biodiversity effects - ecosystem functioning - functional trait approach

Biodiversity–ecosystem functioning (BEF) studies typically show that species richness enhances community biomass, but the underlying mechanisms remain debated. Here, we combine metrics from BEF research that distinguish the contribution of dominant species (selection effects, SE) from those due to positive interactions such as resource partitioning (complementarity effects, CE) with a functional trait approach in an attempt to reveal the functional characteristics of species that drive community biomass in species mixtures. In a biodiversity experiment with 16 plant species in monocultures, 4-species and 16-species mixtures, we used aboveground biomass to determine the relative contributions of CE and SE to biomass production in mixtures in the second, dry year of the experiment. We also measured root traits (specific root length, root length density, root tissue density and the deep root fraction) of each species in monocultures and linked the calculated community weighted mean (CWM) trait values and trait diversity of mixtures to CE and SE. In the second year of the experiment, community biomass, CE and SE increased compared to the first year. The contribution of SE to this positive effect was greater than that of CE. The increased contribution of SE was associated with root traits: SE increased most in communities with high abundance of species with deep, thick and dense roots. In contrast, changes in CE were not related to trait diversity or CWM trait values. Together, these results suggest that increased positive effects of species richness on community biomass in a dry year were mainly driven by increased dominance of deep-rooting species, supporting the insurance hypothesis of biodiversity. Positive CE indicates that other positive interactions did occur, but we could not find evidence that belowground resource partitioning or facilitation via root trait diversity was important for community productivity in our biodiversity experiment.

Plant functional diversity and nutrient availability can improve restoration of floating fens via facilitation, complementarity and selection effects
Zuidam, Jeroen P. van; Leeuwen, Casper H.A. van; Bakker, Elisabeth S. ; Verhoeven, Jos T.A. ; Ijff, Stéphanie ; Peeters, Edwin T.H.M. ; Zuidam, Bastiaan G. van; Soons, Merel B. - \ 2018
Journal of Applied Ecology (2018). - ISSN 0021-8901
assisted colonization - floating fen - functional diversity - peat formation - restoration - rhizome formation - terrestrialization - wetlands

Peat-forming wetlands, particularly floating fens that form the initial stages of these ecosystems, are declining globally due to excavation, dehydration and eutrophication. Restoration typically involves reestablishment of early-successional open-water stages, with oligotrophic conditions that are characteristic for these systems. However, restoration success is notoriously limited. A potential improvement may be to initiate succession by reintroducing of target plant species. Knowledge is therefore needed on (a) which plant functional groups should be re-introduced to stimulate fen formation; and (b) how to manage nutrient levels during restoration, considering that plant growth may be slow in oligotrophic conditions. We hypothesized that increasing functional diversity of introduced species would stimulate the formation of peat-forming target communities, their biomass accumulation and expansion onto open water. We also hypothesized that nutrient availability would mediate the relative contribution of specific functional groups to these effects. We investigated this in 36 artificial outdoor ponds by manipulating plant functional diversity (clonal dominants, clonal stress-tolerators and interstitials) on constructed rafts with fen-forming communities, and subjected these to a range of nutrient loadings over 2 years. Increasing functional diversity as well as increasing nutrient loadings had stimulating effects on plant biomass accumulation, cover formation and rhizome growth onto open water. Both complementarity (due to niche partitioning or facilitation) and selection effects were mechanisms underlying the diversity effect, with a constant relative importance over the entire range of nutrient availabilities. Different functional groups were important for biomass production at different nutrient availabilities. Rhizome formation by clonal stress-tolerators contributed disproportionately to open water colonization, identifying this functional group as key across all nutrient levels. Synthesis and applications. Restoration of floating fen communities can be stimulated during the first 2 years by introducing a high functional diversity of plant species. There include fast-growing clonal species, clonal stress-tolerators and interstitials, which facilitate each other. Restoration is dependent on the presence of clonal stress-tolerators such as Calla palustris, Comarum palustre and Menyanthes trifoliata for expansion onto the open water. Furthermore, restoration can start under a wide range of water nutrient levels, including eutrophic conditions.

WUR bloembollen verhuist naar Bleiswijk
Bakker, Sjaak ; Poot, Eric - \ 2018
Ditr P79_Characterisation of PLETHORA during gall formation of the root-knot nematode Meloidogyne incognita
Oosterbeek, Matthijs ; Overmars, H.A. ; Scheres, B.J.G. ; Bakker, J. ; Goverse, A. - \ 2018
The parasitic root-knot nematode Meloidogyne incognita manipulates developmental processes in plants through formation of large tumour-like structures, designated as galls, in the roots of their hosts. The transcriptional profile of these galls show significant overlap with that of the formation of lateral roots (Cabrera et al., 2014). Key regulators in the formation of lateral roots are the PLETHORA (PLT) transcription factors PLT3, PLT5 and PLT7. They are induced by the sustained presence of the phytohormone auxin. These genes work together to regulate positioning and outgrowth of lateral root primordia (Hofhuis et al., 2013). The auxin efflux proteins PINFORMED (PIN) are thought to play an important role in this process and PLTs are known to regulate them in plants (Prasad et al., 2011). During the initial development of nematode-induced galls an accumulation of auxin is observed (Karczmarek et al., 2004). Additionally PIN proteins are known to be involved in gall formation (Kyndt et al., 2016). However, how the PIN proteins are regulated upon root-knot nematode infection is unknown. Hence, we studied the possibility that the PLT-PIN module is used during the formation of feeding sites of M. incognita. Mutant lines of the PLT genes showed a decrease in the number of infections and in number of reproducing females as compared to the wild type lines. Additionally, in several mutant lines galls developed that were significantly increased in size. Moreover, the auxin exporter PIN3 in the mutant line of the three PLT genes was no longer localised at the plasma membranes of cells within the feeding site in contrast to the wild type lines. We conclude that the three PLT genes are involved in feeding site initiation and development and could potentially achieve this through regulation of PIN.
Can the Land Use Master Plan Control Urban Expansion and Protect Farmland in China? A Case Study of Nanjing
Shao, Zinan ; Spit, Tejo ; Jin, Zhifeng ; Bakker, Martha ; Wu, Qun - \ 2018
Growth and Change 49 (2018)3. - ISSN 0017-4815 - p. 512 - 531.

Urbanization represents a challenge for plans aimed at controlling urban expansion and protecting farmland, such as the land use master plan (LUMP) instituted by the Chinese national government. This paper studies the effectiveness of such top–down plans under the authoritarian regime through the case study of Nanjing. In contrast to previous studies that compare actual and planned land-use maps, we compare actual and planned land-use patterns. We use land-use change data to examine spatio-temporal land-use change between the years 1997 and 2014. The results indicate that the actual amount of urban-rural built-up land exceeded planned regulatory amount by 50,185 ha and the total farmland was 70,541 ha less than the target outlined in the LUMP (1997–2010). Based on these results, and the fact that the allowed total urban-rural built-up land had already been surpassed in 2014, it is to be expected that the target of farmland protection outlined in the LUMP (2006–2020) will be broken, signaling the ineffectiveness of the plan to control urban expansion and protect farmland. Plan-led developments (e.g., new towns, development zones) and market forces (e.g., housing market, foreign direct investment) explain these developments. This study indicates that when cities embrace “growth-led” development and entrepreneurial governance, the ability of plans to control urban expansion and protect farmland is severely limited.

Changes in root architecture of Arabidopsis thaliana induced by the cyst nematode Heterodera schachtii
Willig, J. ; Sonneveld, Devon ; Sterken, M.G. ; Lozano Torres, J.L. ; Goverse, A. ; Bakker, J. ; Smant, G. - \ 2018
Low levels of infection by cyst nematodes on some resistant crop varieties result in significant loss in yield, while other heavily infected varieties show hardly any symptoms at all. This difference in responses suggests that some plants tolerate biotic stress by plant parasitic nematodes better than others. The objective of our current research is to investigate whether Arabidopsis thaliana can be used to unravel the genetic architecture and molecular mechanisms underlying differences in tolerance to plant parasitic nematodes in plants. To this end we first looked at changes in root architecture upon inoculation with increasing numbers of the beet cyst nematode Heterodera schachtii. This revealed how plants could compensate for damage induced by cyst nematodes in roots at low inoculation densities. Altogether, our data may demonstrate if Arabidopsis can be used as a model to study tolerance to cyst nematodes in plants.
Minder watergebruik in tuinbouw Saudi-Arabië
Bakker, J.C. - \ 2018
Onder Glas 15 (2018)5. - p. 43 - 43.
Warming enhances sedimentation and decomposition of organic carbon in shallow macrophyte-dominated systems with zero net effect on carbon burial
Velthuis, Mandy ; Kosten, Sarian ; Aben, Ralf ; Kazanjian, Garabet ; Hilt, Sabine ; Peeters, Edwin T.H.M. ; Donk, Ellen van; Bakker, Elisabeth S. - \ 2018
Global Change Biology 24 (2018)11. - ISSN 1354-1013 - p. 5231 - 5242.
carbon cycle - decomposition - global warming - mineralization - phenology - primary production - sedimentation - submerged aquatic plant

Temperatures have been rising throughout recent decades and are predicted to rise further in the coming century. Global warming affects carbon cycling in freshwater ecosystems, which both emit and bury substantial amounts of carbon on a global scale. Currently, most studies focus on the effect of warming on overall carbon emissions from freshwater ecosystems, while net effects on carbon budgets may strongly depend on burial in sediments. Here, we tested whether year-round warming increases the production, sedimentation, or decomposition of particulate organic carbon and eventually alters the carbon burial in a typical shallow freshwater system. We performed an indoor experiment in eight mesocosms dominated by the common submerged aquatic plant Myriophyllum spicatum testing two temperature treatments: a temperate seasonal temperature control and a warmed (+4°C) treatment (n = 4). During a full experimental year, the carbon stock in plant biomass, dissolved organic carbon in the water column, sedimented organic matter, and decomposition of plant detritus were measured. Our results showed that year-round warming nearly doubled the final carbon stock in plant biomass from 6.9 ± 1.1 g C in the control treatment to 12.8 ± 0.6 g C (mean ± SE), mainly due to a prolonged growing season in autumn. DOC concentrations did not differ between the treatments, but organic carbon sedimentation increased by 60% from 96 ± 9.6 to 152 ± 16 g C m−2 yaer−1 (mean ± SE) from control to warm treatments. Enhanced decomposition of plant detritus in the warm treatment, however, compensated for the increased sedimentation. As a result, net carbon burial was 40 ± 5.7 g C m−2 year−1 in both temperature treatments when fluxes were combined into a carbon budget model. These results indicate that warming can increase the turnover of organic carbon in shallow macrophyte-dominated systems, while not necessarily affecting net carbon burial on a system scale.

Orchestration of transcriptome, proteome and metabolome in the diatom Phaeodactylum tricornutum during nitrogen limitation
Remmers, Ilse M. ; Adamo, Sarah D'; Martens, Dirk E. ; Vos, Ric C.H. de; Mumm, Roland ; America, Antoine H.P. ; Cordewener, Jan H.G. ; Bakker, Linda V. ; Peters, Sander A. ; Wijffels, René H. ; Lamers, Packo P. - \ 2018
Algal Research 35 (2018). - ISSN 2211-9264 - p. 33 - 49.
Diatoms - Diurnal metabolism - Lipids - Mitochondrion - Omics - Triacylglycerol

Nitrogen deprivation increases the triacylglycerol (TAG) content in microalgae but also severely decreases the growth rate. Most approaches that attempted to increase TAG productivity by overexpression or knockdown of specific genes related to the regulation of the lipid synthesis have reported only little success. More insight into the molecular mechanisms related to lipid accumulation and impaired growth rate is needed to find targets for improving TAG productivity. By using the emerging “omics” approach, we comprehensively profiled the physiology, transcriptome, proteome and metabolome of the diatom Phaeodactylum tricornutum during steady state growth at both nitrogen limited and replete levels during light:dark cycles. Under nitrogen limited conditions, 22% (2699) of the total identified transcripts, 17% (543) of the proteins and 44% (345) of the metabolites were significantly differentially regulated compared to nitrogen replete growth conditions. Although nitrogen limitation was responsible for the majority of significant differential transcript, protein and metabolite accumulation, we also observed differential expression over a diurnal cycle. Nitrogen limitation mainly induced an upregulation of nitrogen fixation, central carbon metabolism and TCA cycle, while photosynthetic and ribosomal protein synthesis are mainly downregulated. Regulation of the lipid metabolism and the expression of predicted proteins involved in lipid processes suggest that lipid rearrangements may substantially contribute to TAG distribution. However, TAG synthesis is also limited by the reduced carbon flux through central metabolism. Future strain improvements should therefore focus on understanding and improving the carbon flux through central carbon metabolism, selectivity and activity of DGAT isoforms and lipase enzymes.

An Evaluation of the Loss-on-Ignition Method for Determining the Soil Organic Matter Content of Calcareous Soils
Hoogsteen, M.J.J. ; Lantinga, E.A. ; Bakker, E.J. ; Tittonell, P.A. - \ 2018
Communications in Soil Science and Plant Analysis 48 (2018)13. - ISSN 0010-3624 - p. 1541 - 1552.
Calcite analysis procedures - ignition temperature - sample weight

The Loss-on-Ignition (LOI) method is widely employed for measuring the organic matter (OM) content of soil samples. There is a risk of carbonate losses when calcareous soil samples are analyzed through LOI, but this has never been investigated in detail. Moreover, a worldwide standard protocol for determining the carbonate content of soils is not available. The aims of this study were (i) to evaluate two commonly employed carbonate analysis procedures using calcareous and non-calcareous soil samples: the gravimetric method with (GMF) and without (GM) the addition of the antioxidant iron(II) chloride (FeCl2) and the acetic acid dissolution procedure (AAD); (ii) to evaluate the effect of ignition temperature on losses of pure calcite, calcite-quartz and calcareous soil samples. We found that the average apparent carbonate content of the non-calcareous soils was greatest for the GMF method followed by the AAD procedure. The GM method showed the smallest apparent carbonate contents. For the calcite-quartz sand mixture, ignition losses started at 600°C and increased with temperature in a sigmoidal way. LOI values stabilized at 750°C when 80% of the carbon dioxide was released. We recommend the GM procedure for carbonate analysis because the apparent carbonate contents of the non-calcareous soil samples were smallest. Furthermore, we recommend an LOI temperature of 550°C because at this ignition temperature 99.8% of the total calcite fraction remains in the soil samples.

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