Ole Pedersen

Ole Pedersen
University of Copenhagen · Department of Biology

PhD

About

136
Publications
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Introduction
Torrential rains have hit hard in many parts of the world and many natural wetland plants and also crops become flooded! Submergence tolerance of wetland plants and crops is thus currently a hot topic and we use our expertise in underwater photosynthesis and internal aeration in a suite of projects with national and internal partners. Currently, we are focusing on root and leaf traits that confer flood tolerance to both aquatic and terrestrial plants. The traits include superhydrophobic leaves and gas film retention during submergence and internal aeration facilitated by aerenchyma formation, barriers to radial oxygen loss and tolerance to soil phytotoxins produced in waterlogged soils as waste products by anaerobic bacteria. We welcome further international collaboration on these topics.
Additional affiliations
January 2010 - present
Utrecht University
January 2007 - present
Radboud University
January 2006 - present
University of Western Australia

Publications

Publications (136)
Article
Throughout the freshwater continuum, Dissolved Organic Carbon (DOC) and the colored fraction, Chromophoric Dissolved Organic Material (CDOM), are continuously being added, removed, and transformed, resulting in changes in the chromophoricity and lability of organic matter over time. We examined, experimentally, the effect of increasing irradiation-...
Article
Background and Aims While trait-based approaches have provided critical insights into general plant functioning, we lack a comprehensive quantitative view on plant strategies in flooded conditions. Plants adapted to flooded conditions have specific traits (e.g. root porosity, low root/shoot ratio and shoot elongation) to cope with the environmental...
Article
In flooded soils, an efficient internal aeration system is essential for root growth and plant survival. Roots of many wetland species form barriers to restrict radial O2 loss (ROL) to the rhizosphere. The formation of such barriers greatly enhances longitudinal O2 diffusion from basal parts towards the root tip, and the barrier also impedes the en...
Article
The root barrier to radial O2 loss (ROL) is a trait enabling waterlogging tolerance of plants. The ROL barrier restricts O2 diffusion to the anoxic soil so that O2 is retained inside root tissues. We hypothesised that the ROL barrier can also restrict radial diffusion of other gases (H2 and water vapour) in rice roots with a barrier to ROL. We use...
Article
C4 perennial Urochloa spp. grasses are widely planted in extensive areas in the tropics. These areas are continuously facing waterlogging events, which limits plant growth and production. However, no commercial cultivar combining excellent waterlogging tolerance with superior biomass production and nutritional quality is available. The objective of...
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(1) Drought and flooding are contrasting abiotic stressors for plants. Evidence is accumulating for root anatomical traits being essential for the adaptation to drought or flooding. However, an integrated approach to comprehensively understand root anatomical traits has not yet been established. (2) Here we analysed the root anatomical traits of 18...
Article
Flooding is an environmental stress that leads to a shortage of O2 that can be detrimental for plants. When flooded, deepwater rice grow floating adventitious roots to replace the dysfunctional soil-borne root system but the features that ensure O2 supply and hence growth of aquatic roots have not been explored. We investigate the sources of O2 in...
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Heavy rainfall causes flooding of natural ecosystems as well as farmland, negatively affecting plant performance. While the responses of the wild model organism Arabidopsis thaliana to such stress conditions is well understood, little is known about the responses of its relative, the important oil crop plant Brassica napus. For the first time, we a...
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The leaf economics spectrum (LES) describes consistent correlations among a variety of leaf traits that reflect a gradient from conservative to acquisitive plant strategies. So far, whether the LES holds in wetland plants at a global scale has been unclear. Using data on 365 wetland species from 151 studies, we find that wetland plants in general s...
Article
This Expert View provides an update on the recent development of new microsensors, and briefly summarizes some novel applications of existing microsensors, in plant biology research. Two major topics are covered, i) sensors for gaseous analytes (O2, CO2, H2S) and ii) those for measuring concentrations and fluxes of ions (macro- and micronutrients a...
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Flooding causes oxygen deprivation in soils. Plants adapt to low soil oxygen availability by changes in root morphology, anatomy, and architecture to maintain root system functioning. Essential traits include aerenchyma formation, a barrier to radial oxygen loss, and outgrowth of adventitious roots into the soil or the floodwater. We highlight rece...
Article
Plants have developed a suite of traits to survive the anaerobic and anoxic soil conditions in wetlands. Previous studies on wetland plant adaptive traits have focused mainly on physiological aspects under experimental conditions, or compared the trait expression of the local species pool. Thus, a comprehensive analysis of potential factors driving...
Article
Plants typically respond to waterlogging by producing new adventitious roots with aerenchyma and many wetland plants form a root barrier to radial O2 loss (ROL), but it was not known if this was also the case for lateral roots. We tested the hypothesis that lateral roots arising from adventitious roots can form a ROL barrier, using root‐sleeving el...
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The molecular mechanisms controlling underwater elongation are based extensively on studies on internode elongation in the monocot rice (Oryza sativa) and petiole elongation in Rumex rosette species. Here we characterize underwater growth in the dicot Nasturtium officinale (watercress), a wild species of the Brassicaceae family, in which submergenc...
Article
Roots in flooded soils experience hypoxia, with least O2 in the vascular cylinder. Gradients in CO2 across roots had not previously been measured. The respiratory quotient (RQ; CO2 produced: O2 consumed) is expected to increase as O2 availability declines. A new CO2 microsensor, and an O2 microsensor, were used to measure profiles across roots of c...
Article
Unlike in land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to carbon dioxide (CO 2) to compensate for the low diffusivity and potential depletion of CO 2 in water. Concentrations of bicarbonate and CO 2 vary greatly with catchment geology. In this study, we investigate whether there is a link between these concen...
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Complex multicellular organisms evolved on Earth in an oxygen-rich atmosphere¹; their tissues, including stem-cell niches, require continuous oxygen provision for efficient energy metabolism². Notably, the maintenance of the pluripotent state of animal stem cells requires hypoxic conditions, whereas higher oxygen tension promotes cell differentiati...
Article
Deepwater rice has a remarkable shoot elongation response to partial submergence. Shoot elongation to maintain air-contact enables 'snorkelling' of O2 to submerged organs. Previous research has focused on partial submergence of deepwater rice. We tested the hypothesis that leaf gas films enhance internode O2 status and stem elongation of deepwater...
Article
Waterlogged soils contain monocarboxylic acids produced by anaerobic microorganisms. These ‘organic acids’ can accumulate to phytotoxic levels and promote development of a barrier to radial O2 loss (ROL) in roots of some wetland species. Environmental cues triggering root ROL barrier induction, a feature which together with tissue gas‐filled porosi...
Article
Increasing terrestrial input of colored dissolved organic matter (CDOM) to temperate softwater lakes has reduced transparency, distribution of pristine rosette plants and overall biodiversity in recent decades. We examined microbial and UV-induced reduction of absorption by CDOM and dissolved organic carbon pools (DOC) in humic water from a groundw...
Chapter
Life in seawater presents several challenges for seagrasses owing to low O2 and CO2 solubility and slow gas diffusion rates. Seagrasses have evolved numerous adaptations to these environmental conditions including porous tissue providing low-resistance internal gas channels (aerenchyma) and carbon concentration mechanisms involving the enzyme carbo...
Article
Background and aims: Leaf tissue CO2 partial pressure (pCO2) shows contrasting dynamics over a diurnal cycle in C3 and Crassulacean Acid Metabolism (CAM) plants. However, simultaneous and continuous monitoring of pCO2 and pO2 in C3 and CAM plants under the same conditions was lacking. Our aim was to use a new CO2 microsensor and an existing O2 mic...
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Responses of wheat (Triticum aestivum) to complete submergence are not well understood as research has focused on waterlogging (soil flooding). The aim of this study was to characterize the responses of two wheat cultivars differing vastly in submergence tolerance to test if submergence tolerance was linked to shoot carbohydrate consumption as seen...
Article
The presence of oxygen in seagrass tissues, which plays a role in preventing seagrass die-off, is partly regulated by environmental conditions. Here, we examined the relationship between oxygen (O2) in the rhizomes of Posidonia sinuosa and key environmental variables at Garden Island, Western Australia. We made in situ measurements of internal oxyg...
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Floods impede gas (O2 and CO2) exchange between plants and the environment. A mechanism to enhance plant gas exchange under water comprises gas films on hydrophobic leaves, but the genetic regulation of this mechanism is unknown. We used a rice mutant (dripping wet leaf 7, drp7) which does not retain gas films on leaves, and its wild-type (Kinmaze)...
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Groundwater-borne contaminants such as nutrients, dissolved organic carbon (DOC), coloured dissolved organic matter (CDOM) and pesticides can have an impact the biological quality of lakes. The sources of pollutants can, however, be difficult to identify due to high heterogeneity in groundwater flow patterns. This study presents a novel approach fo...
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Background and aims: Soil waterlogging adversely impacts most plants. Melilotus siculus is a waterlogging-tolerant annual forage legume, but data were lacking for the effects of root-zone hypoxia on nodulated plants reliant on N2 fixation. The aim was to compare the waterlogging tolerance and physiology of M. siculus reliant on N2 fixation or with...
Article
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Groundwater borne contaminants such as e.g., nutrients, dissolved organic carbon (DOC), coloured dissolved organic matter (CDOM) and pesticides impact the biological quality of lakes. The sources of pollution can, however, be difficult to identify due to high heterogeneity in groundwater flow patterns. This study presents a novel approach for fast...
Article
Lake Constance is the second largest lake in Europe. While naturally oligotrophic, the lake experienced a period of heavy eutrophication due to the input of domestic and industrial sewage and agricultural runoff in the 1960s and 1970s. This prompted concerted efforts from authorities to purify wastewaters and reduce agricultural nutrient input, ini...
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Background and aims: Floating sweet-grass ( Glyceria fluitans ) can form aerial as well as floating leaves, and these both possess superhydrophobic cuticles, so that gas films are retained when submerged. However, only the adaxial side of the floating leaves is superhydrophobic, so the abaxial side is directly in contact with the water. The aim of...
Article
Full-text available
Flooding of fields after sudden rainfall events can result in crops being completely submerged. Some terrestrial plants, including wheat (Triticum aestivum L.), possess superhydrophobic leaf surfaces that retain a thin gas film when submerged, and the gas films enhance gas exchange with the floodwater. However, the leaves lose their hydrophobicity...
Article
Full-text available
Submergence invokes a range of stressors to plants with impeded gas exchange between tissues and floodwater being the greatest challenge. Many terrestrial plants including wheat (Triticum aestivum L.), possess superhydrophobic leaf cuticles that retain a thin gas film when submerged, and the gas films enhance gas exchange with the floodwater. Howev...
Article
Terrestrial saltmarsh plants inhabiting flood-prone habitats undergo recurrent and prolonged flooding driven by tidal regimes. In this study, the role of internal plant aeration in contrasting hypoxic/anoxic conditions during submergence was investigated in the two halophytes Limonium narbonense Mill. and Sarcocornia fruticosa (L.) A.J. Scott. Moni...
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The world is currently experiencing dramatic increases in flood events impacting on natural vegetation and crops. Flooding often results in low O2 status in root tissues during waterlogging, but sometimes also in shoot tissues when plants become completely submerged. Plants possess a suite of traits enabling tissue aeration and/or adjusted metaboli...
Article
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HIGHLIGHTS: Sedimentation of fine sediment particles onto seagrass leaves severely hampers the plants' performance in both light and darkness, due to inadequate internal plant aeration and intrusion of phytotoxic H2S. Anthropogenic activities leading to sediment re-suspension can have adverse effects on adjacent seagrass meadows, owing to reduced...
Article
Lake Hampen, (Central Jutland, Denmark) is located high in the landscape near a seasonal moving groundwater divide. The lake is regarded as a flow-through lake during average to wet weather conditions with a large catchment making the lake groundwater-dominated. Monitoring of δ¹⁸O in mini-piezometers in the lake bed and wells at the lake shore and...
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Apart from playing a key role in important biochemical reactions, molecular oxygen (O2) and its by-products also have crucial signaling roles in shaping plant developmental programs and environmental responses. Even under normal conditions, sharp O2 gradients can occur within the plant when cellular O2 demand exceeds supply, especially in dense org...
Article
The submerged aquatic freshwater macrophyte Isoetes australis S. Williams grows in rock pools situated in south-western Australia, an environment where dissolved inorganic phosphorus (Pi) availability possibly limits growth. In contrast to the two coexisting aquatic species, Glossostigma drummundii and Crassula natans, I. australis did not form rel...
Article
Floods and salinization of agricultural land adversely impact global rice production. We investigated whether gas films on leaves of submerged rice delay salt entry during saline submergence. Two-week-old plants with leaf gas films (+GF) or with gas films experimentally removed (−GF) were submerged in artificial floodwater with 0 or 50 mM NaCl for...
Article
Seagrasses grow submerged in aerated seawater but often in low O2 sediments. Elevated temperatures and low O2 are stress factors. Internal aeration was measured in two tropical seagrasses, Thalassia hemprichii and Enhalus acoroides, growing with extreme tides and diel temperature amplitudes. Temperature effects on net photosynthesis (PN ) and dark...
Article
Traits for survival during flooding of terrestrial plants include stimulation or inhibition of shoot elongation, aerenchyma formation, and efficient gas exchange. Leaf gas films form on superhydrophobic cuticles during submergence and enhance underwater gas exchange. The main hypothesis tested was that the presence of leaf gas films influences the...
Article
Full-text available
We review the detrimental effects of waterlogging on physiology, growth and yield of wheat. We highlight traits contributing to waterlogging tolerance and genetic diversity in wheat. Death of seminal roots and restriction of adventitious root length due to O2 deficiency result in low root:shoot ratio. Genotypes differ in seminal root anoxia toleran...
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Photosynthesis of most seagrass species seems to be limited by present concentrations of dissolved inorganic carbon (DIC). Therefore, the ongoing increase in atmospheric CO2 could enhance seagrass photosynthesis and internal O2 supply, and potentially change species competition through differential responses to increasing CO2 availability among spe...
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The general premise for successful archaeological in situ preservation in wetlands is that raising the water table will ‘seal the grave’ by preventing oxygen from reaching the deposit. The present review reveals that this may not be the entire picture, as a change in habitat may introduce new plant species that can damage site stratigraphy and arte...
Article
The presence of epiphytic turf algae may modify the effects of ocean acidification on coralline algal calcification rates by altering seawater chemistry within the diffusive boundary layer (DBL) above coralline algal crusts. We used microelectrodes to measure the effects of turf algal epiphytes on seawater pH and the partial pressure of oxygen (pO2...
Article
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Oxygen deficiency associated with soil waterlogging adversely impacts root respiration and nutrient acquisition. We investigated the effects of O2 deficiency and salinity (100 mM NaCl) on radial O2 concentrations and cell-specific ion distributions in adventitious roots of barley (Hordeum vulgare). Microelectrode profiling measured O2 concentration...
Article
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Many stem-succulent halophytes experience regular or episodic flooding events, which may compromise gas exchange and reduce survival rates. This study assesses submergence tolerance, gas exchange and tissue oxygen (O2) status of two stem-succulent halophytes with different stem diameters and from different elevations of an inland marsh. Responses t...
Chapter
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Submergence impedes plant gas exchange with the environment. Survival depends upon internal aeration to provide O2 throughout the plant body, although short-term anoxia can be tolerated. During nights, plants rely on O2 entry from the floodwater and pO2 in roots declines so that some tissues become severely hypoxic or even anoxic. Underwater photos...
Article
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Most functional feeding types are represented within the species rich group of aquatic chironomids. Thus, we hypothesized that different lake types and microhabitats within lakes would (1) host specific chironomid communities and (2) that the individual communities would show specific δ 13C stable isotope signatures reflecting the prevailing origin...
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Floods can completely submerge some rice (Oryza sativa L.) fields. Leaves of rice have gas films that aid O2 and CO2 exchange under water. The present study explored the relationship between gas film persistence and underwater net photosynthesis (PN) as influenced by genotype and submergence duration. Four contrasting genotypes (FR13A, IR42, Swarna...
Article
Full-text available
Some terrestrial wetland plants, such as rice, have super-hydrophobic leaf surfaces which retain a gas film when submerged. O2 movement through the diffusive boundary layer (DBL) of floodwater, gas film and stomata into leaf mesophyll was explored by means of a reaction-diffusion model that was solved in a 3D leaf anatomy model. The anatomy and dar...
Article
The root and shoot tissues of flooding tolerant wetland plants are highly porous to enable internal gas phase diffusion of O2 during waterlogging or submergence. In the case of only partial submergence (snorkeling), the atmosphere can act as source of O2 . The aim of this study was to assess the effect of waterlogging, partial submergence and compl...
Article
A combination of flooding and salinity is detrimental to most plants. We studied tolerance of complete submergence in saline water for Melilotus siculus, an annual legume with superhydrophobic leaf surfaces that retain gas films when under water. M. siculus survived complete submergence of one week at low salinity (up to 50 mol m(-3) NaCl), but did...
Article
Full-text available
Global climate change has increased flooding events, which affect both natural vegetation dynamics and crop productivity. The flooded environment is lethal for most plant species because it restricts gas exchange and induces an energy and carbon crisis. Flooding survival strategies have been studied in Oryza sativa, a cultivated monocot. However, o...
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We describe the general background and the recent advances in research on underwater photosynthesis of leaf segments, whole communities, and plant dominated aquatic ecosystems and present contemporary methods tailor made to quantify photosynthesis and carbon fixation under water. The majority of studies of aquatic photosynthesis have been carried o...