Carbon isotope composition of middle Eocene leaves from the Messel Pit, Germany

A b s t r a c t The 13 C/ 12 C ratios (δ 13 C) of leaves from the middle Eocene of the Messel Pit (Middle Messel Formation) were measured to determine the ratios of leaf-internal to ambient carbon dioxide concentration (c i /c a ) for the respective time. For extant plants this parameter provides information about their ecophysiological state. Fossil leaves belonging to three species were analyzed: Laurophyllum lanigeroides (Lauraceae), Daphnogene crebrigranosa (Lauraceae) and Rhodomyrtophyllum sinuatum (Myrtaceae). In order to determine the range of δ 13 C across a single leaf (intra-leaf variability) samples from the basal, central and apical region were separately prepared and analyzed. The results are compared to δ 13 C and c i /c a ratios in extant evergreen Lauraceae (Laurus nobilis, Cinnamomum camphora, Persea americana) and Myrtaceae (Myrtus communis, Psidium littorale/cattleianum). The δ 13 C of the fossil cuticles varies from -30 ‰ to -27 ‰ in the Lauraceae and from -29 ‰ to -26 ‰ in the Myrtaceae, which are typical ranges for extant C 3 -plants. Results of intra-leaf analyses indicate that δ 13 C varies slightly across the leaves but intra-leaf variability is statistically not signifi cant. Mean Eocene c i /c a -ratios as calculated from the measured δ 13 C values varied from 0.78 to 0.87. The c i /c a -ratios of extant Lauraceae are substantially lower (average 0.69) than for the fossil material. In Myrtaceae, c i /c a -ratios are almost the same for extant and fossil material (extant Myrtaceae average at about 0.8). K e y w o r d s : middle Eocene, Messel, leaves, carbon isotopes, c i /c a -ratio. Z u s a m m e n f a s s u n g Das 13 C/ 12 C-Verhältnis (δ 13 C) von fossilen Blättern aus dem Mitteleozän der Grube Messel (Mittlere Messel Formation) wurde gemessen und daraus das Verhältnis von blattinternem zu atmosphärischem Kohlendioxid (c i /c a ) für die betreffende Zeit bestimmt. Bei heutigen Pfl anzen erlaubt diese Größe eine Einschätzung des ökophysiologi-schen Zustands. Es wurden die Blätter von drei fossilen Arten analysiert: Laurophyllum lanigeroides (Lauraceae), Daphnogene crebrigranosa (Lauraceae) und Rhodomyrtophyllum sinuatum (Myrtaceae). Um Schwankungen des δ 13 C innerhalb eines Blattes (blattinterne Variabilität) bestimmen zu können, wurden getrennte Proben aus dem basalen, dem mittleren und dem apikalen Bereich genommen und analysiert. Die Ergebnisse wurden mit dem δ 13 C und c i /c a rezenter immergrüner Lauraceae (Laurus nobilis, Cinnamomum camphora, Persea americana) und Myrtaceae (Myrtus communis, Psidium littorale/cattleianum) verglichen. Das δ 13 C der fossilen Kutikulen variiert von -30 ‰ bis -27 ‰ innerhalb der Lauraceae und von -29 ‰ bis -26 ‰ innerhalb der Myrtaceae, was im Bereich moderner C 3 -Pfl anzen liegt. Die Ergebnisse der blattinternen Analysen zeigen, dass der δ 13 C-Wert innerhalb eines Blattes variiert, diese blattinterne Variabilität statistisch jedoch nicht signifi kant ist. Das c i /c a -Verhältnis für das Mitteleozän, das mit den gemessenen δ 13 C-Werten berechnet wurde, schwankt zwischen durchschnittlich 0,78 und 0,87. Die c i /c a -Verhältnisse für rezente Lauraceae sind deutlich geringer (durchschnittlich 0,69) als die für die beiden fossilen Arten errechneten Werte. Bei den Myrtaceae unterscheiden sich die mitteleozänen und rezenten c i /c a -Verhältnisse kaum, rezente Myrtaceae liegen hier durchschnittlich bei etwa 0,8

Competition between diffusion and advection may mediate self-repair of wax microstructures on plant surfaces

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. Waxes are produced within the epidermal cells, then transported to the leaf surface and finally integrated into the polymer or deposited upon the cuticle. Remarkably, damaged wax layers may become repaired within a few hours. Base on an earlier hypothesis we present a theoretical framework explaining how waxes are transported through the plant epidermis by a combination of advection and diffusion. This combination suggests also a self-regulating repair mechanism, based on the assumption that intact cuticles induce an antagonistic equilibrium between advection and diffusion: whenever a wax layer is damaged, the equilibrium is disturbed in favour of advection, starting a repair process, which is intrinsically coming to an end after the cuticle has gained its original thickness

Drop Traffic in Microfluidic Ladder Networks with Fore-Aft Structural Asymmetry

We investigate the dynamics of pairs of drops in microfluidic ladder networks with slanted bypasses, which break the fore-aft structural symmetry. Our analytical results indicate that unlike symmetric ladder networks, structural asymmetry introduced by a single slanted bypass can be used to modulate the relative drop spacing, enabling them to contract, synchronize, expand, or even flip at the ladder exit. Our experiments confirm all these behaviors predicted by theory. Numerical analysis further shows that while ladder networks containing several identical bypasses are limited to nearly linear transformation of input delay between drops, mixed combination of bypasses can cause significant non-linear transformation enabling coding and decoding of input delays.Comment: 4 pages, 5 figure

Quantifying loopy network architectures

Biology presents many examples of planar distribution and structural networks having dense sets of closed loops. An archetype of this form of network organization is the vasculature of dicotyledonous leaves, which showcases a hierarchically-nested architecture containing closed loops at many different levels. Although a number of methods have been proposed to measure aspects of the structure of such networks, a robust metric to quantify their hierarchical organization is still lacking. We present an algorithmic framework, the hierarchical loop decomposition, that allows mapping loopy networks to binary trees, preserving in the connectivity of the trees the architecture of the original graph. We apply this framework to investigate computer generated graphs, such as artificial models and optimal distribution networks, as well as natural graphs extracted from digitized images of dicotyledonous leaves and vasculature of rat cerebral neocortex. We calculate various metrics based on the Asymmetry, the cumulative size distribution and the Strahler bifurcation ratios of the corresponding trees and discuss the relationship of these quantities to the architectural organization of the original graphs. This algorithmic framework decouples the geometric information (exact location of edges and nodes) from the metric topology (connectivity and edge weight) and it ultimately allows us to perform a quantitative statistical comparison between predictions of theoretical models and naturally occurring loopy graphs.Comment: 17 pages, 8 figures. During preparation of this manuscript the authors became aware of the work of Mileyko at al., concurrently submitted for publicatio

The Late Eocene 187Os / 188Os excursion : chemostratigraphy, cosmic dust flux and the early Oligocene glaciation

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 241 (2006): 477-492, doi:10.1016/j.epsl.2005.11.035.High resolution records (ca. 100 kyr) of Os isotope composition (187Os/188Os) in bulk sediments from two tropical Pacific sites (ODP Sites 1218 and 1219) capture the complete Late Eocene 187Os/188Os excursion and confirm that the Late Eocene 187Os/188Os minimum, earlier reported by Ravizza and Peucker-Ehrenbrink [Earth Planet. Sci. Lett. 210 (2003) 151-165], is a global feature. Using the astronomically tuned age models available for these sites, it is suggested that the Late Eocene 187Os/188Os minimum can be placed at 34.5±0.1 Ma in the marine records. In addition, two other distinct features of the 187Os/188Os excursion that are correlatable among sections are proposed as chemostratigraphic markers which can serve as age control points with a precision of ca. ±0.1 Myr. We propose a speculative hypothesis that higher cosmic dust flux in the Late Eocene may have contributed to global cooling and early Oligocene glaciation (Oi-1) by supplying bio-essential trace elements to the oceans and thereby resulting in higher ocean productivity, enhanced burial of organic carbon and draw down of atmospheric CO2. To determine if the hypothesis that enhanced cosmic dust flux in the Late Eocene was a cause for the 187Os/188Os excursion can be tested by using the paired bulk sediment and leachate Os isotope composition, 187Os/188Os were also measured in sediment leachates. Results of analyses of leachates are inconsistent between the south Atlantic and the Pacific sites, and therefore do not yield a robust test of this hypothesis. Comparison of 187Os/188Os records with high resolution benthic foraminiferal δ18O records across the Eocene-Oligocene transition suggests that 187Os flux to the oceans decreased during cooling and ice growth leading to the Oi-1 glaciation, whereas subsequent decay of ice-sheets and deglacial weathering drove seawater 187Os/188Os to higher values. Although the precise timing and magnitude of these changes in weathering fluxes and their effects on the marine 187Os/188Os records are obscured by recovery from the Late Eocene 187Os/188Os excursion, evidence of the global influence of glaciation on supply of Os to the ocean is robust as it has now been documented in both Pacific and Atlantic records.This study was supported by NSF awards OCE-0118380, EAR-0215297 and EAR-0215297

New constraints on atmospheric CO2 concentration for the Phanerozoic

Earth's atmospheric CO2 concentration (ca) for the Phanerozoic Eon is estimated from proxies and geochemical carbon cycle models. Most estimates come with large, sometimes unbounded uncertainty. Here, we calculate tightly constrained estimates of ca using a universal equation for leaf gas exchange, with key variables obtained directly from the carbon isotope composition and stomatal anatomy of fossil leaves. Our new estimates, validated against ice cores and direct measurements of ca, are less than 1000 ppm for most of the Phanerozoic, from the Devonian to the present, coincident with the appearance and global proliferation of forests. Uncertainties, obtained from Monte Carlo simulations, are typically less than for ca estimates from other approaches. These results provide critical new empirical support for the emerging view that large (~2000-3000 ppm), long-term swings in ca do not characterize the post-Devonian and that Earth's long-term climate sensitivity to ca is greater than originally thought. Key Points A novel CO2 proxy calculates past atmospheric CO2 with improved certainty CO2 is unlikely to have exceeded ~1000 ppm for extended periods post Devonian Earth's long-term climate sensitivity to CO2 is greater than originally thought

Separating foliar physiology from morphology reveals the relative roles of vertically structured transpiration factors within red maple crowns and limitations of larger scale models

A spatially explicit mechanistic model, MAESTRA, was used to separate key parameters affecting transpiration to provide insights into the most influential parameters for accurate predictions of within-crown and within-canopy transpiration. Once validated among Acer rubrum L. genotypes, model responses to different parameterization scenarios were scaled up to stand transpiration (expressed per unit leaf area) to assess how transpiration might be affected by the spatial distribution of foliage properties. For example, when physiological differences were accounted for, differences in leaf width among A. rubrum L. genotypes resulted in a 25% difference in transpiration. An in silico within-canopy sensitivity analysis was conducted over the range of genotype parameter variation observed and under different climate forcing conditions. The analysis revealed that seven of 16 leaf traits had a ≥5% impact on transpiration predictions. Under sparse foliage conditions, comparisons of the present findings with previous studies were in agreement that parameters such as the maximum Rubisco-limited rate of photosynthesis can explain ∼20% of the variability in predicted transpiration. However, the spatial analysis shows how such parameters can decrease or change in importance below the uppermost canopy layer. Alternatively, model sensitivity to leaf width and minimum stomatal conductance was continuous along a vertical canopy depth profile. Foremost, transpiration sensitivity to an observed range of morphological and physiological parameters is examined and the spatial sensitivity of transpiration model predictions to vertical variations in microclimate and foliage density is identified to reduce the uncertainty of current transpiration predictions

Biomimetic transferable surface for a real time control over wettability and photoerasable writing with water drop lens

We demonstrate a transferable device that can turn wettability of surfaces to sticky or slippy, as per requirement. It is composed of polymeric yarn with a fibrous structure, which can be lifted and placed on any surface to render it the unique wettability properties. We introduce Polyvinylidenefluoride (PVDF) random fiber as biomimetic rose petal surface. When it is decorated with PVDF nanofibers yarns, the random mesh transform from rose petal sticky state into grass leaf slippy state. When it is placed on sticky, hydrophilic metal coin, it converts the surface of the coin to super hydrophobic. Adjustments in the yarn system, like interyarn spacing, can be done in real time to influence its wettability, which is a unique feature. Next, we load the polymer with a photochromic compound for chemical restructuring. It affects the sliding angle of water drop and makes the fibers optically active. We also demonstrate a “water droplets lens” concept that enables erasable writing on photochromic rose petal sticky fibrous surface. The droplet on a highly hydrophobic surface acts as a ball lens to concentrate light onto a hot spot; thereby we demonstrate UV light writing with water lenses and visible light erasing