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

High Productivity at High Latitudes? Photosynthesis and Leaf Ecophysiology in Arctic Forests of the Eocene

AbstractThe Arctic forests of the Eocene, which thrived under elevated CO2, a temperate climate, high precipitation and annually extremely different daylengths, represent a quite spectacular no‐analogue habitat of Earth's greenhouse past. The aim of this study was to improve our understanding of the ecophysiology of Arctic broad‐leaved deciduous forests of the Eocene, by analyzing leaf photosynthesis and tree productivity based on gas exchange modeling for two fossil Eocene sites, Svalbard and Ellesmere Island. For this, a single‐leaf photosynthesis model that includes heat transfer and leaf senescence was derived. Environmental conditions were based on available palaeoclimate data and a CO2 level of 800 μmol/mol. Additionally, different light regimes (diffusivity and transmissivity) were considered. With this model, annual photosynthesis was calculated on the basis of annual temperature and day lengths (derived by celestial mechanics). To obtain productivity of a whole deciduous broad‐leaved tree, the single leaf data were then upscaled by a canopy model. The results indicate that productivity was enhanced at both high latitude sites by elevated CO2, temperature of the growing season and high maximum daylength (24 hr) during late spring and early summer. With productivity values about 30%–60% higher as for a mid‐latitude continental European forest, the results indicate a potential for high productivity at the Eocene polar sites which is in the range of extant tropical forests. In contrast to speculations, no evidence for a selective advantage of large leaf size—as shown by various fossil leaves from high latitude sites—could be found.Plain Language Summary: Greenhouse conditions of the past allowed forests to thrive in the Arctic. The productivity of early Eocene broad‐leaved trees, growing about 55–45 million years ago within the Arctic circle, was studied by applying physiological models to the climate conditions of the past. The Arctic environment during that time was non‐analogous, meaning that today there is no spot on Earth showing the same conditions which included a temperate climate, ample precipitation, 24 hr of daylight during early summer and a CO2 concentration twice as high as today's CO2 concentration. It was found that under these conditions, tree productivity is up to about 30%–60% higher as that of an extant temperate mid‐latitude forest. Knowledge on the ecology of high‐latitude environments of past greenhouse periods can provide valuable information for possible climate change scenarios of the future.Key Points: Lush forests thrived in the Arctic during the Eocene under non‐analogous climatic conditions Tree productivity of Eocene forests was studied for two exemplary fossil Arctic sites based on a photosynthesis model Compared to extant deciduous forests, productivity of Arctic Eocene forests was in the range of modern tropical forests ftp://palantir.boku.ac.at/Public/MODIS_EUROhttps://land.copernicus.eu/pan-european/corine-land-cover/clc201

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

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

From tree to architecture: how functional morphology of arborescence connects plant biology, evolution and physics

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 ecological niches for other organisms, such as epiphytes, creating a vast amount of habitats. During land plant evolution, a variety of different tree constructions evolved and their constructional principles are a subject of ongoing research. Understanding the “natural construction” of trees benefits strongly from methods and approaches from physics and engineering. Plant water transport is a good example for the ongoing demand for interdisciplinary efforts to unravel form-function relationships on vastly differing scales. Identification of the unique mechanism of water long-distance transport requires a solid basis of interfacial physics and thermodynamics. Studying tree functions by using theoretical approaches is, however, not a one-sided affair: The complex interrelationships between traits, functionality, trade-offs and phylogeny inspire engineers, physicists and architects until today.Staatliches Museum für Naturkunde Stuttgart (SMNS) (4944

Stomatal Crypts Have Small Effects on Transpiration: A Numerical Model Analysis1

Stomata arranged in crypts with trichomes are commonly considered to be adaptations to aridity due to the additional diffusion resistance associated with this arrangement; however, information on the effect of crypts on gas exchange, relative to stomata, is sparse. In this study, three-dimensional Finite Element models of encrypted stomata were generated using commercial Computational Fluid Dynamics software. The models were based on crypt and stomatal architectural characteristics of the species Banksia ilicifolia, examined microscopically, and variations thereof. In leaves with open or partially closed stomata, crypts reduced transpiration by less than 15% compared with nonencrypted, superficially positioned stomata. A larger effect of crypts was found only in models with unrealistically high stomatal conductances. Trichomes inside the crypt had virtually no influence on transpiration. Crypt conductance varied with stomatal conductance, boundary layer conductance, and ambient relative humidity, as these factors modified the three-dimensional diffusion patterns inside crypts. It was concluded that it is unlikely that the primary function of crypts and crypt trichomes is to reduce transpiration