Wilfried Konrad

Wilfried Konrad
University of Tuebingen | EKU Tübingen · Department of Geosciences

Dr. rer.nat., Dr. rer.nat.habil.

About

63
Publications
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935
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Publications

Publications (63)
Article
Full-text available
Raindrop impact on leaves is a common event which is of relevance for numerous processes, including the dispersal of pathogens and propagules, leaf wax erosion, gas exchange, leaf water absorption, and interception and storage of rainwater by canopies. The process of drop impact is complex, and its outcome depends on many influential factors. The w...
Article
Full-text available
The floating leaves of the aquatic fern Salvinia molesta are covered by super-hydrophobic hairs (=trichomes) which are shaped like egg-beaters. These trichomes cause high water repellency and stable unwettability if the leaf is immersed. Whereas S. molesta hairs are technically interesting, there remains also the question concerning their biologica...
Article
The determination of the dynamic contact angle is of significant interest for the characterization of the wettability of technical fibers and textiles in diverse fields of science and technology. There exist traditional methods for dynamic contact angle measurements of flat surfaces and of fibers with a uniform cross‐sectional shape along the fiber...
Article
Full-text available
Trees are the fundamental element of forest ecosystems, made possible by their mechanical qualities and their highly sophisticated conductive tissues. The evolution of trees, and thereby the evolution of forests, were ecologically transformative and affected climate and biogeochemical cycles fundamentally. Trees also offer a substantial amount of e...
Article
Full-text available
Aerial roots of orchids are able to absorb atmospheric water (e.g. rain, mist, dew) and to conduct it to the root interior. The water is absorbed by imbibition into a biological porous material, the velamen radicum, which envelops the aerial root and comprises one or two to several layers. The velamen radicum consists of walls of dead cells and sho...
Article
Full-text available
A variety of proxies have been developed to reconstruct paleo‐CO2 from fossil leaves. These proxies rely on some combination of stomatal morphology, leaf δ13C, and leaf gas exchange. A common conceptual framework for evaluating these proxies is lacking, which has hampered efforts for inter‐comparison. Here we develop such a framework, based on the...
Article
Full-text available
There is general concern that the rapid increase in atmospheric CO2 concentration will lead to reduced stomatal conductance and subsequent increases in leaf temperature. Such an increase in leaf temperature is expected to adversely impact a plethora of processes connected to leaf metabolism and microbial/fungal communities on leaves. A model is pro...
Article
Leaves are the most appropriate plant organs for studying adaptations to environmental changes as they are the locations of photosynthetic metabolism and thus directly exposed to habitat conditions. Besides investigations on complete assemblages, individual long-ranging species could directly mirror adaptations and changes of leaf traits on environ...
Article
In frost hardy plants, the lethal intracellular formation of ice crystals has to be prevented during frost periods. Besides the ability for supercooling and pre-frost dehydration of tissues, extracellular ice forma- tion is another strategy to control ice development in tissues. During extracellular ice formation, partially large ice bodies accumul...
Article
Functional properties of biological surfaces have gained increasing interest in the last two decades, especially with regard to wetting and self-cleaning. Here, biological surfaces of arthropods (Collembola) and plants (sacred Lotus) served as models for the principle design of high temperature resistant surfaces used in blast furnaces to prevent t...
Article
Proxy estimates of atmospheric CO2 are necessary to reconstruct Earth's climate history. Confidence in paleo-CO2 estimates can be increased by comparing results from multiple proxies at a single site, but so far this strategy has been implemented only for marine-based techniques. Here we present CO2 estimates for the well-studied early Paleocene Ca...
Article
Xylem and phloem are the two main conveyance systems in plants allowing exchanges of water and carbohydrates between roots and leaves. While each system has been studied in isolation for well over a century, the coupling and coordination between them remains the subject of inquiry and active research and frames the scope of the review here. Using a...
Presentation
During land plant evolution many groups developed the ability to survive freezing events. Extracellular freezing is an essential process, it accompanies cell dehydration mechanism and protects the living tissue from internal damage which would be evoked by intracellular ice crystal growth. Within our project we studied freezing of various frost har...
Article
Correlations of leaf traits with environmental conditions are widely used for reconstruction of palaeoclimate and to analyse the evolution of land plants. Evaluation of climate-dependent leaf traits of fossil floras can potentially contribute to our understanding of long-term responses of vegetation to changing climate. In this contribution, basic...
Chapter
Cuticles are extracellular membranes covering the primary aerial parts of vascular plants. They consist of a multifunctional polymeric material with embedded soluble components called waxes, and serve as the interface between plants and their atmospheric environment, first of all protecting them from desiccation. Remarkably, damaged wax layers may...
Article
To address questions related to the acceleration or deceleration of the global hydrological cycle or links between the carbon and water cycles over land, reliable data for past climatic conditions based on proxies are required. In particular, the reconstruction of palaeoatmospheric CO2 content (Ca) is needed to assist the separation of natural from...
Chapter
Aerial roots of epiphytic orchids cannot absorb water from the soil but supply the plant by collecting atmospheric water together with dissolved nutrients. A special outer tissue layer, the velamen radicum (VR), consisting of dead cells, is crucial for water interception and absorption. In this contribution, the VR is explored as an intricate porou...
Article
Full-text available
Recently, several leaf fossils with good cuticles were discovered from the Oligocene deposits in Guangxi, China. The high fossilization potential of these leaves and easily identifiable stomata and epidermal cells make them an excellent source for CO2 reconstruction. In this study, atmospheric CO2 of the Oligocene is reconstructed using the mechani...
Article
Full-text available
Glandular trichomes of the carnivorous plant Roridula gorgonias release a viscous resinous secretion. Its adhesion to hydrophilic and hydrophobic glass surfaces was measured in air and underwater. The underwater adhesion reached up to 91% (on hydrophilic glass) and 28% (on hydrophobic glass) of that measured in the air. After being submersed for 24...
Article
There is various evidence that the presence of condensed water, e.g. dew, improves plant water relations. Since particularly plants in drier environments are expected to benefit from atmospheric water, it may be assumed that special adaptations promoting exploitation of dew water evolved in these habitats. Surface characteristics affect dewfall and...
Article
The late Oligocene represents a comparatively cool phase followed by a warming event, the so-called Late Oligocene Warming that predates the Mi-1 glacial event at the Oligocene–Miocene transition. There is evidence that these climate events were linked to level changes in atmospheric CO2. In this study, atmospheric CO2 from the late Oligocene to th...
Article
Full-text available
In the Cenozoic era, global climate changed from greenhouse to icehouse conditions. During the Oligocene, the comparatively cool phase in the earlier part of the late Oligocene is followed by the Late Oligocene Warming and a major glaciation event at the Oligocene-Miocene transition (Mi-1). Various studies indicate that these climate events were co...
Article
Full-text available
Background and AimsCold neutron radiography was applied to directly observe embolism in conduits of liana stems with the aim to evaluate the suitability of this method for studying embolism formation and repair. Potential advantages of this method are a principally non-invasive imaging approach with low energy dose compared with synchrotron X-ray r...
Article
It has repeatedly been reported that stomatal pore length changes with changing atmospheric CO2 concentration. Since stomatal pore length affects stomatal conductance, the question arises of how pore length change interacts with the application of stomatal density as a CO2 proxy. In this study, stomatal density, pore length and maximum stomatal con...
Article
Full-text available
The Namib grass Stipagrostis sabulicola relies, to a large degree, upon fog for its water supply and is able to guide collected water towards the plant base. This directed irrigation of the plant base allows an efficient and rapid uptake of the fog water by the shallow roots. In this contribution, the mechanisms for this directed water flow are ana...
Article
Full-text available
During photosynthesis, plants inevitably lose water that has to be continuously replaced by soil water absorbed by the roots. Hydrological status of the soil, root absorption, plant water transport, gas exchange and atmosphere are therefore intricately coupled within the soil-plant-atmosphere continuum (SPAC). It appears therefore straighforward to...
Article
In this study, atmospheric CO2 during the early middle Eocene (~ 47Ma) is reconstructed using fossil plants from the Messel Formation close to Darmstadt, Germany. CO2 concentration is calculated using a mechanistic model of gas exchange which optimizes CO2 uptake by photosynthesis against water vapor loss by transpiration, a strategy that is common...
Article
Full-text available
Wettability and retention capacity of leaf surfaces are parameters that contribute to interception of rain, fog or dew by forest canopies. Contrary to common expectation, hydrophobicity or wettability of a leaf do not dictate the stickiness of drops to leaves. Crucial for the adhesion of drops is the contact angle hysteresis, the difference between...
Article
Full-text available
Background: Controlled transport of microdroplets is a topic of interest for various applications. It is well known that liquid droplets move towards areas of minimum contact angle if placed on a flat solid surface exhibiting a gradient of contact angle. This effect can be utilised for droplet manipulation. In this contribution we describe how con...
Conference Paper
Full-text available
For various plants and animals, the accumulation of fog or dew droplets constitutes an essential part of their water supply. Understanding how water droplets deposited by fog or dew events interact with plant or animal surfaces is essential for gaining insight into the functionality of these surfaces. Besides being interesting within the realm of b...
Article
The Oligocene-Miocene transition represents a period in earth history marked by rapid cooling and glaciation of Antarctica, accompanied by a positive shift in delta13C and delta18O. According to modelling studies, formation of substantial Antarctic ice sheets requires pCO2atm to decrease below 500 ppm. Various proxies (such as Boron isotopes and de...
Article
Various proxies (such as pedogenic carbonates, boron isotopes or phytoplankton) and geochemical models were applied in order to reconstruct palaeoatmospheric carbon dioxide, partially providing conflicting results. Another promising proxy is the frequency of stomata (pores on the leaf surface used for gaseous exchange). In this project, fossil plan...
Article
We present a systematic derivation of the relation between stomatal density and CO2concentration based upon (i) a quantitative model of C3-photosynthesis, (ii) the physics of diffusion, and (iii) an optimisation principle which asserts that plants adjust stomatal conductance such that assimilation is maximised and transpiration is minimised. Since...
Article
We describe a few mathematical tools which allow to investigate whether air-water interfaces exist (under prescribed conditions) and are mechanically stable and temporally persistent. In terms of physics, air-water interfaces are governed by the Young-Laplace equation. Mathematically they are surfaces of constant mean curvature which represent solu...
Article
Full-text available
Gas-filling of conduits decreases hydraulic conductance of the xylem vessels. Therefo re, embolism formation and reversal is one of the crucial topics in plant water transport. The negative pressure (=tension) in xylem water during plant transpiration may cause embolism in tw o ways: (i) Homogeneous nucleation, the spontaneous formation of a water...
Article
It is assumed that changes in atmospheric CO2 concentrations (from now on expressed as Ca) strongly influenced the development of global temperatures during parts of the Cenozoic. Thus, detailed knowledge of ancient Ca and its variations is of utmost importance for exploring the coupling of atmospheric CO2 and global climate change. Numerous techni...
Article
Full-text available
In this study, contaminant leaching from three different secondary materials (demolition waste, municipal solid waste incineration ash, and blast furnace slag) to groundwater is assessed by numerical modeling. Reactive transport simulations for a noise protection dam and a road dam (a typical German autobahn), in which secondary materials are reuse...
Article
Stomatal density tends to vary inversely with changes in atmospheric CO(2) concentration (C(a)). This phenomenon is of significance due to: (i) the current anthropogenic rise in C(a) and its impact on vegetation, and (ii) the potential applicability for reconstructing palaeoatmospheric C(a) by using fossil plant remains. It is generally assumed tha...
Article
Full-text available
In this study, groundwater contamination from recycled demolition waste in road constructions is assessed using predictions of leachate concentrations. Numerical transport simulations are performed for three scenarios ( a parking lot, a noise protection barrier, and road), and using a number of characteristic subsoils of Germany, to estimate the br...
Article
The often observed reciprocal change of stomatal density (SD) or stomatal index (SI) with atmospheric CO2 has led to the utilization of this phenomenon as a CO2 proxy for past paleoclimates. Usually, data of the SD or SI(CO2) relationship of extant plants are used for empirical calibration in order to calculate past CO2 with fossil stomatal data. I...
Article
A mechanistic model (Konrad &Roth-Nebelsick a, in prep.) was applied for the reconstruction of atmospheric carbon dioxide using stomatal densities and photosynthesis parameters of extant and fossil Fagaceae. The model is based on an approach which couples diffusion and the biochemical process of photosynthesis. Atmospheric CO2 is calculated on the...
Article
Full-text available
During plant water transport, the water in the conducting tissue (xylem) is under tension. The system is then in a metastable state and prone to bubble development and subsequent embolism blocking further water transport. It has recently been demonstrated, that embolism can be repaired under tension (= novel refilling). A model (Pit Valve Mechanism...
Article
Gaseous exchange in land plants occurs via micropores on the plant surface, the stomata. The stomatal frequency (SF) of leaves has attracted considerable interest with respect to increasing atmospheric CO2 since Woodward (1987) demonstrated that this parameter changes inversely with CO2 in various species. The response is due to 1) individual pheno...
Article
The characteristic basic construction of early land plants with an upright posture is represented by a simple leaf- and rootless axis system with a central conducting bundle (‘rhyniophytic habit’). Variations of this simple architectural principle in different early land plant taxa probably reflect different ecophysiological requirements. In this c...
Article
Pressure-induced tensions in the xylem, the water conducting tissue of vascular plants, can lead to embolism in the water-conducting cells. The details and mechanisms of embolism repair in vascular plants are still not well understood. In particular, experimental results which indicate that embolism repair may occur during xylem tension cause great...
Article
Full-text available
Early terrestrial ancestors of the land flora are characterized by a simple, axially symmetric habit and evolved in an atmosphere with much higher CO(2)concentrations than today. In order to gain information about the ecophysiological interrelationships of these plants, a model dealing with their gaseous exchange, which is basic to transpiration an...
Article
Full-text available
83C05 Einstein's equations (general structure, canonical formalism, Cauchy problems) 83C15 Exact solutions 83C57 Black holes
Article
Full-text available
A model system, consisting of a thin spherical shell with radiusR and massM and a point massm at a distances>R from the center of the sphere, held fixed by an appropriate strut, is solved to ordermM. The stresses in the shell are not of the canonical Weyl type, and it is argued that the same is true for more realistic situations, e.g., rotating mat...

Projects

Projects (3)
Project
The aim of this project was the eco physiological study and analyzing of the leaf surface of Stipagrostris sabulicola, species of Poaceae endemic of the Namib desert. The results were used to produce an efficient filter able to generate potable water through mist filtration.
Project
This project had the objective of transferring the morphological and physiological characteristics of the capillaries and vessel elements of lianas, for the production of a technical water transport systems.
Project
NECLIME is an open international network of scientists working on Cenozoic climate evolution and related changes of continental ecosystems. During the past 65 million years of Earth history, globally warmer-then-present conditions prevailed in a world with almost modern paleogeography. These timespans represent promising case studies for anticipated future scenarios. Within the NECLIME network, we aim to combine data on past climate change and its environmental impact for large-scale reconstructions. NECLIME research activities comprise paleoclimate reconstructions, including atmospheric CO₂ and ecosystem analysis using multiple quantitative methods on various primarily continental proxies (plants; vertebrates; invertebrates; geochemistry and geological proxies). Complementing model studies are employed to assess connections and processes driving ocean, atmosphere and biosphere at global and regional scales. NECLIME was established in 1999 with the aim to understand Neogene trends across Eurasia. This basic idea quickly and constantly expanded to a global interest and a wider stratigaphical frame. The steadily growing NECLIME network with currently around 140 members in 34 countries is coordinated by a team of researchers and an advisory board. NECLIME holds annual conferences and workshops and administers working groups bringing forward scientific exchange, joint projects, and the integration of research data. For more information go to www.neclime.de