Institut für Botanik und Landschaftsökologie & Botanischer Garten
Refine
Year of publication
Document Type
- Article (108)
- Doctoral Thesis (62)
Has Fulltext
- yes (170)
Is part of the Bibliography
- no (170)
Keywords
- - (65)
- climate change (17)
- dendrochronology (9)
- paludiculture (9)
- rewetting (7)
- forest ecology (6)
- peatland (6)
- Jahresring (5)
- Moor (5)
- boreal forest (5)
Institute
Publisher
- MDPI (34)
- Frontiers Media S.A. (23)
- Wiley (22)
- Springer Nature (8)
- Elsevier (5)
- Nature Publishing Group (5)
- IOP Publishing (4)
- SAGE Publications (3)
- BioMed Central (BMC) (1)
- Copernicus (1)
Background
Plants are designed to endure stress, but increasingly extreme weather events are testing the limits. Events like flooding result in submergence of plant organs, triggering an energy crisis due to hypoxia and threaten plant growth and productivity. Lipids are relevant as building blocks and energy vault and are substantially intertwined with primary metabolism, making them an ideal readout for plant stress.
Results
By high resolution mass spectrometry, a distinct, hypoxia-related lipid composition of Solanum lycopersicum root tissue was observed. Out of 491 lipid species, 11 were exclusively detected in this condition. Among the lipid classes observed, glycerolipids and glycerophospholipids dominated by far (78%). Differences between the lipidomic profiles of both analyzed conditions were significantly driven by changes in the abundance of triacylglycerols (TGs) whereas sitosterol esters, digalactosyldiacylglycerols, and phosphatidylcholine play a significantly negligible role in separation. Alongside, an increased level of polyunsaturation was observed in the fatty acid chains, with 18:2 and 18:3 residues showing a significant increase. Of note, hexadecatetraenoic acid (16:4) was identified in hypoxia condition samples. Changes in gene expression of enzymes related to lipid metabolism corroborate the above findings.
Conclusion
To our knowledge, this is the first report on a hypoxia-induced increase in TG content in tomato root tissue, closing a knowledge gap in TG abiotic stress response. The results suggest that the increase in TGs and TG polyunsaturation degree are common features of hypoxic response in plant roots.
Climate change is expected to outpace the rate at which populations of forest trees can migrate. Hence, in forestry there is growing interest in intervention strategies such as assisted migration to mitigate climate change impacts. However, until now the primary focus when evaluating candidates for assisted migration has been mean or maximum performance. We explore phenotypic plasticity as a potentially new avenue to help maintain the viability of species and populations in the face of climate change. Capitalizing on large, multi-site international provenance trials of four economically and ecologically important forest tree species ( Fagus sylvatica , Picea abies , Picea engelmannii , Pinus contorta ), we quantify growth stability as the width of the response function relating provenance growth performance and trial site climate. We found significant differences in growth stability among species, with P. engelmannii being considerably more stable than the other three species. Additionally, we found no relationship between growth performance and growth stability of provenances, indicating that there are fast-growing provenances with a broad climate optimum. In two of the four species, provenances’ growth stability showed a significant relationship with the climate of the seed source, the direction of which depends on the species. When taken together with data on growth performance in different climate conditions, a measure of growth stability can improve the choice of species and provenances to minimize future risks in forest restoration and reforestation.
Coastal wetlands, including lagoons, marshes, and peatlands, are exceptionally important ecosystems that provide many ecosystem services and functions, and exert a substantial influence on global climate. As global climate change progresses, permafrost and ice sheets will continue to thaw and sea levels will rise, in turn causing inundation of coastal wetlands, such as thermokarst lakes, peatlands, and salt marshes. Inundation of sea water will also bring sulfate to freshwater systems, potentially reducing methane emissions, but also producing other negative ecosystems responses, such increased nutrient release, including dissolved organic carbon, ammonium, phosphate, iron, and many others. This thesis discusses the results of three studies from two coastal wetlands investigating the impact of sulfate on the biogeochemistry and microbial ecology of these sites, in conjunction with results from other studies.
In study 1, two thermokarst lakes and a thermokarst lagoon took the form of a natural laboratory to investigate how sulfate intrusion impacted the methane-cycling microbial community by altering the geochemistry of the lagoon. In addition to changes in the geochemistry, marine water intrusion also introduced and provided habitat for classical marine consortia of sulfate reducers and anaerobic methane oxidizers called ANME, which formed an effective filter on methane produced in the sediments. Sulfate intrusion also reformed the microbial community, and did not follow classical marine biogeochemical process zonation.
In study 2, the effects of brackish water rewetting on greenhouse gas dynamics in a previously drained and freshened peatland were investigated. Monitoring activities were conducted before and after rewetting to determine if brackish water rewetting was an effective way to reduce methane emissions in rewetted peatlands. Initial results showed that methane emissions were reduced compared to similar freshwater peatland rewetting projects, however carbon dioxide release remained higher than expected.
Study 3 examined whether the microbial community from the same field site as study 2 was adapted to the new conditions two years post-rewetting. In an incubation experiment, soil samples from three depths were subjected to two different salinity regimes, representing the range of expected salinities experienced by the microbial community since rewetting over the course of 3 months, with special attention paid to differences in biogeochemistry and the microbial community. Contrary to expectations, the largest influence on biogeochemistry and the microbial community came from legacy sulfate deposits from when the site was previously connected to the Baltic Sea as a brackish marsh in the early 1900s.
The overall picture of sulfate intrusion and methane cycling is somewhat clouded. In general, increased sulfate concentrations do lower methane emissions, but also induces increased releases of other nutrients. One part of the larger solution to curtailing methane emissions in natural systems, especially those impacted by anthropogenic activities, could be increased methanotrophy which is not necessarily reliant on sulfate. A plan forward is proposed in the synthesis, which encourages more research into the topic of sulfate introduction to freshwater systems and a different way to tackle methane emissions through encouraging natural mitigation through microbial methanotrophy.
Hypoxic environmental conditions such as flooding and the resulting oxygen limitation for plant roots interrupt oxidative phosphorylation and lead to an energy crisis in plants. The energy shortage eventually results in the breakdown of cellular transmembrane gradients and cell death. The degradation of sucrose and starch and an increase in anaerobic glycolysis are well-described mechanisms to provide energy and survive this crisis. Lactic acid and ethanolic fermentation recycle reducing equivalents to maintain ATP synthesis. However, alternative reducing equivalent oxidation mechanisms (Chapter I), alternative energy and carbon sources (Chapter II) and regulation of energy consumption (Chapter III) can be crucial for survival under low oxygen conditions. To answer this hypothesis, emissions of nitric oxide (NO) under low-oxygen conditions (mechanism – Chapter I), changes in lipid composition under hypoxic conditions (energy source – Chapter II) and a redox-reactive and highly conserved cysteine residue of a plasma membrane (PM) P-type H+-ATPase (energy consumption – Chapter III) were investigated.
The thesis confirmed the importance of nitrite (NO2-) as an alternative electron acceptor resulting in NO emissions of plant roots during low-oxygen stress. Firstly, the chemiluminescence-based detection of oxygen-dependent NO emissions in in vivo studies for roots of tomato, barley and tobacco is reported using a root reactor (Chapter I). The large amounts of low-oxygen NO emission in the root reactor suggest a role in generation of ATP. NO2- reduction appears to be involved in the mitochondrial electron transfer chain (mETC) and therefore may contribute to ATP generation. In response to oxygen depletion, an escape strategy of the studied species seems likely, including oxygen supply systems. In this strategy, additional ATP is invested to integrate structural changes. However, hypoxic tomato plants seem to rely on glycolysis and fermentation. They do not utilize lipid degradation and β-oxidation as energy source which was confirmed in HPLC-MS-MS analysis studies of hypoxic tomato roots (Chapter II). In terms of energy source, neither a depletion of lipids nor an increase in lipid degradation was observed. Triacylglycerol (TG) was more abundant and the degree of unsaturation of fatty acids increased due to hypoxic conditions (Chapter II). TGs play a role as intermediates in lipid metabolism. Subsequent utilization of carbon and energy sources during prolonged oxygen scarcity is possible. However, an altered activity of PM P-type H+-ATPase due to hypoxic-induced, posttranslational NO modification was not confirmed. A possible S-nitrosylation site at the conserved cysteine residue was not verified in the biochemical mutagenesis study described in Chapter III. Regulation of PM P-type H+-ATPase activity via cytoplasmatic ATP-level may be possible in plants.
The maintenance of proteins and cell functions appears to be essential under conditions of low-oxygen and high levels of reactive nitrogen species (RNS) such as NO (Chapter I). The induction of antioxidant systems under low-oxygen stress is well known. In this thesis, the highly conserved cysteine near the P-site of the PM P-type H+-ATPase was shown to act as an endogenous antioxidant (Chapter III). This underlines the importance of this enzyme for the cell. While the changes in lipid composition observed under hypoxia highlight the importance of maintaining membrane integrity and fluidity as in the case of plastids (Chapter II). Membrane adaptation results in increased TG abundance which led to the formation of lipid droplets. TG may scavenge toxic intermediates to prevent cell death. Lipid droplets provide a binding site for enzymes involved in adaptation and may even protect unsaturated fatty acids under high reactive oxygen species (ROS) and RNS environments by being incorporated into their core.
Under low-oxygen conditions, various strategies have evolved to provide sufficient energy for adaptation and survival while protecting vital cellular functions in plants. The increase in flooding and heavy rainfall due to climate change poses a challenge to crops and their harvest. Plant-based stress-responses may even be a factor impacting the climate (Chapter I). In order to stabilize food production, plant breeding may need to rethink breading strategies in certain areas. With more heavy rains and same annual rain fall a quiescence strategy via growth retention may sometimes be better than an escape strategy to save crucial energy under time-limited stress conditions. A better understanding of survival mechanisms, as provided in this thesis, may help to develop strategies that strengthen plants under mild low-oxygen conditions.
Flood events are likely to increase in the near future and are one of the events most threatening to agricultural production. Barley is the fourth most important crop and the cereal most sensitive to excessive moisture stress. Improving the stress tolerance of crops to a variety of stress factors caused by a more volatile climate is an important task for the coming years. The aim of this study was to investigate the efficacy of cold atmospheric plasma-treated water (PTW) as a foliar spray to stimulate the antioxidant system of Hordeum vulgare and thereby improve plant stress tolerance. For this purpose, we analysed the components of the ascorbate-glutathione cycle in barley leaves and roots without stress and under waterlogging conditions. PTW increased the content of total and reduced ascorbate in leaves as well as the content of reduced ascorbate in roots four weeks after treatment. This was observed both, under stress free conditions and after waterlogging and re-aeration. In leaves, enzyme activities also increased after re-aeration, and in roots, total and reduced glutathione levels increased after waterlogging compared to the control. The accumulation of low molecular weight antioxidants may increase tolerance to a variety of stress factors through more efficient scavenging of ROS. Overall, treatment of plants with PTW may trigger an adaptive response that leads to mitigation of the negative effects of stress, and thus, could be used as a priming agent for protection against subsequent more severe stress factors that occur in the plants' natural environment.
In 2011, MoorFutures® were introduced as the first standard for generating credits from peatland rewetting. We developed methodologies to quantify ecosystem services before and after rewetting with a focus on greenhouse gas emissions, water quality, evaporative cooling and mire-typical biodiversity. Both standard and premium approaches to assess these services were developed, and tested in the rewetted polder Kieve (NE-Germany). The standard approaches are default tier 1 estimation procedures, which require little time and few, mainly vegetation data. Based on the Greenhouse gas Emission Site Type (GEST) approach, emissions decreased from 1,306 t CO2e in the baseline scenario to 532 t CO2e in the project scenario, whereas 5 years after rewetting they were assessed to be 543 t CO2e per year. Nitrate release assessed via Nitrogen Emission Site Types (NEST) was estimated to decrease from 1,088 kg N (baseline) to 359 kg N (project), and appeared to be 309 kg N per year 5 years after rewetting. The heat flux − determined with Evapotranspiration Energy Site Types (EEST) – decreased from 6,691 kW (baseline) to 1,926 kW (project), and was 2,250 kW per year 5 years after rewetting. Mire-specific biodiversity was estimated to increase from very low (baseline) to high (project), but was only low 5 years after rewetting. The premium approaches allow quantifying a particular ecosystem service with higher accuracy by measuring or modelling. The approaches presented here have been elaborated for North-Germany but can be adapted for other regions. We encourage scientists to use our research as a model for assessing peatland ecosystem services including biodiversity in other geographical regions. Using vegetation mapping and indicator values derived from meta-analyses is a cost-efficient and robust approach to inform payment for ecosystem services schemes and to support conservation planning at regional to global scales.
In the species groups related to Diphasiastrum multispicatum and D. veitchii, hybridization was investigated in samples from northern and southern Vietnam and the island of Taiwan, including available herbarium specimens from southeast Asia. The accessions were analyzed using flow cytometry (living material only), Sanger sequencing and multiplexed inter-simple sequence repeat genotyping by sequencing. We detected two cases of ancient hybridization involving different combinations of parental species; both led via subsequent duplication to tetraploid taxa. A cross D. multispicatum × D. veitchii from Malaysia represents D. wightianum, a tetraploid taxon according to reported DNA content measurements of dried material (genome formulas MM, VV and MMVV, respectively). The second case involves D. veitchii and an unknown diploid parent (genome formula XX). Three hybridogenous taxa (genome formulas VVX, VVXX, VVVX) were discernable by a combination of flow cytometry and molecular data. Taxon I (VVX, three clones found on Taiwan island) is apparently triploid. Taxon II represents another genetically diverse and sexual tetraploid species (VVXX) and can be assigned to D. yueshanense, described from Taiwan island but occurring as well in mainland China and Vietnam. Taxon III is as well most likely tetraploid (VVVX) and represented by at least one, more likely two, clones from Taiwan island. Taxa I and III are presumably asexual and new to science. Two independently inherited nuclear markers recombine only within, not between these hybrids, pointing towards reproductive isolation. We present an evolutionary scheme which explains the origin of the hybrids and the evolution of new and fully sexual species by hybridization and subsequent allopolyploidization in flat-branched clubmosses.
The initiation of spring leaf-out is a critical determinant of the growing season in trees, affecting primary production and species interactions in forest ecosystems. Variations in the timing of leaf-out among tree species are linked to their differential progression of bud dormancy. However, identifying reliable markers for bud dormancy has been challenging, leaving the connection between the timing of autumn leaf senescence, bud dormancy and spring leaf-out unclear. To test whether species initiating dormancy release earlier also exhibit earlier leaf senescence in autumn and earlier leaf-out in spring, we estimated the dates of peak dormancy depth (PDD), senescence timing and spring leaf-out across various species, locations and experimental conditions in Central Europe. PDD was defined as the date when the maximum thermal sum was required for leaf-out, whereas leaf senescence was assessed through the decrease in leaf greenness. Our findings reveal that PDD timing is a more accurate predictor of species-level differences in spring leaf-out dates than the timing of leaf senescence, the latter being a poor proxy for PDD. The observed temporal asynchrony between PDD and senescence was linked to dormancy induction showing species-specific sensitivity to temperature variations. Conversely, the timing of leaf senescence showed a consistent reaction to temperature changes across all species. These findings suggest that the physiological processes within buds and leaves during autumn are governed by distinct environmental cues, with the bud dormancy process serving as a more reliable predictor of spring phenological differences among forest tree species than does autumn leaf senescence.
The nivicolous species of the genus Diderma are challenging to identify, and there are several competing views on their delimitation. We analyzed 102 accessions of nivicolous Diderma spp. that were sequenced for two or three unlinked genes to determine which of the current taxonomic treatments is better supported by molecular species delimitation methods. The results of a haplotype web analysis, Bayesian species delimitation under a multispecies coalescent model, and phylogenetic analyses on concatenated alignments support a splitting approach that distinguishes six taxa: Diderma alpinum, D. europaeum, D. kamchaticum, D. meyerae, D. microcarpum and D. niveum. The first two approaches also support the separation of Diderma alpinum into two species with allopatric distribution. An extended dataset of 800 specimens (mainly from Europe) that were barcoded with 18S rDNA revealed only barcode variants similar to those in the species characterized by the first data set, and showed an uneven distribution of these species in the Northern Hemisphere: Diderma microcarpum and D. alpinum were the only species found in all seven intensively sampled mountain regions. Partial 18S rDNA sequences serving as DNA barcodes provided clear signatures that allowed for unambiguous identification of the nivicolous Diderma spp., including two putative species in D. alpinum.
Active afforestation of drained peatlands is not a viable option under the EU Nature Restoration Law
(2024)
The EU Nature Restoration Law (NRL) is critical for the restoration of degraded ecosystems and active afforestation of degraded peatlands has been suggested as a restoration measure under the NRL. Here, we discuss the current state of scientific evidence on the climate mitigation effects of peatlands under forestry. Afforestation of drained peatlands without restoring their hydrology does not fully restore ecosystem functions. Evidence on long-term climate benefits is lacking and it is unclear whether CO2 sequestration of forest on drained peatland can offset the carbon loss from the peat over the long-term. While afforestation may offer short-term gains in certain cases, it compromises the sustainability of peatland carbon storage. Thus, active afforestation of drained peatlands is not a viable option for climate mitigation under the EU Nature Restoration Law and might even impede future rewetting/restoration efforts. Instead, restoring hydrological conditions through rewetting is crucial for effective peatland restoration.