William E. Stein

Giant cladoxylopsid trees resolve the enigma of the Earth's earliest forest stumps at Gilboa

The evolution of trees of modern size growing together in forests fundamentally changed terrestrial ecosystems. The oldest trees are often thought to be of latest Devonian age (about 380–360 Myr old) as indicated by the widespread occurrence of Archaeopteris (Progymnospermopsida). Late Middle Devonian fossil tree stumps, rooted and still in life position, discovered in the 1870s from Gilboa, New York, and later named Eospermatopteris, are widely cited as evidence of the Earth’s ‘oldest forest’. However, their affinities and significance have proved to be elusive because the aerial portion of the plant has been unknown until now. Here we report spectacular specimens from Schoharie County, New York, showing an intact crown belonging to the cladoxylopsid Wattieza (Pseudosporochnales) and its attachment to Eospermatopteris trunk and base. This evidence allows the reconstruction of a tall (at least 8 m), tree-fern-like plant with a trunk bearing large branches in longitudinal ranks. The branches were probably abscised as frond-like modules. Lower portions of the trunk show longitudinal carbonaceous strands typical of Eospermatopteris, and a flat bottom with many small anchoring roots. These specimens provide new insight into Earth’s earliest trees and forest ecosystems. The tree-fern-like morphology described here is the oldest example so far of an evolutionarily recurrent arborescent body plan within vascular plants. Given their modular construction, these plants probably produced abundant litter, indicating the potential for significant terrestrial carbon accumulation and a detritus-based arthropod fauna by the Middle Devonian period.

Surprisingly complex community discovered in the mid-Devonian fossil forest at Gilboa

The origin of trees by the mid-Devonian epoch (398–385 million years ago) signals a major change in terrestrial ecosystems with potential long-term consequences including increased weathering, drop in atmospheric CO2, modified climate, changes in sedimentation patterns and mass extinction. However, little is known about the ecology of early forests or how changes in early terrestrial ecosystems influenced global processes. One of the most famous palaeontological records for this time is the ‘oldest fossil forest’ at Riverside Quarry, Gilboa, New York, USA, discovered in the 1920s. Hundreds of large Eospermatopteris sandstone casts, now thought to represent the bases of standing cladoxylopsid trees, were recovered from a horizon that was originally interpreted as a muddy swamp. After quarry operations ceased, relatively minor outcrops of similar fossils at nearby localities have provided limited opportunities to evaluate this pervasive view using modern methods. In 2010, removal of the quarry backfill enabled reappraisal of the palaeoecology of this important site. Here we describe a 1,200 m2 map showing numerous Eospermatopteris root systems in life position within a mixed-age stand of trees. Unexpectedly, large woody rhizomes with adventitious roots and aerial branch systems identified as aneurophytalean progymnosperms run between, and probably climb into, Eospermatopteris trees. We describe the overall habit for these surprisingly large aneurophytaleans, the earliest fossil group having wood produced by a bifacial vascular cambium. The site also provides evidence for arborescence within lycopsids, extending the North American range for trees in this ecologically critical group. The rooting horizon is a dark grey sandy mudstone showing limited root penetration. Although clearly belonging to a wetland coastal plain environment, the forest was probably limited in duration and subject to periodic disturbance. These observations provide fundamental clarification of the palaeoecology of this mixed-group early forest, with important implications for interpreting coeval assemblage data worldwide.

Semiquinone radical intermediate in catecholic estrogen-mediated cytotoxicity and mutagenesis: Chemoprevention strategies with antioxidants

Modulation of the cytotoxicity and mutagenicity of 4-hydroxyestradiol (4-OHE2), an oxidative metabolite of estrogen, by antioxidants was assessed in human MCF7 cells and TK-6 lymphoblast cells. The cytotoxicity of the catecholic estrogens was potentiated by depletion of intracellular glutathione and was independent of oxygen concentration. Agents such as the nitroxide Tempol can facilitate the oxidation of the semiquinone to the Q and enhanced 4-OHE2 cytotoxicity. Conversely, reducing agents such as ascorbate, cysteine, and 1,4-dihydroxytetramethylpiperidine (THP) protected against cytotoxicity and decreased mutation induction, presumably by reducing the semiquinone to the hydroquinone. Our results support the proposition that oxidation of the semiquinone to the corresponding Q is crucial in eliciting the deleterious effects of catecholic estrogens. Furthermore, because the deleterious effects of 4-OHE2 were abrogated by dietary and synthetic antioxidants, our results would support the chemopreventive use of diets rich in reducing substances (vitamins and added synthetic antioxidants) as a means of decreasing the risks associated with estrogen exposure and developing of breast cancer.

A New Iridopteridalean from the Devonian of Venezuela

The first permineralized Devonian plant fossil is reported here from the Middle or lowermost Upper Devonian of western Venezuela. Two orders of branching plus dichotomous ultimate appendages are known from compressions. A branch of the first order contains a mesarch actinostele with six primary xylem ribs, each with a protoxylem strand near the rib tip (peripheral edge). Compressions of first‐order branches demonstrate three equally spaced lateral organs (higher‐order branches and dichotomous ultimate appendages) attached in whorls, with every other whorl displaying laterals placed in identical orientations and intermediate whorls with laterals offset exactly halfway between. The permineralized specimen partly confirms the presence of whorls and indicates that vascular traces are derived from every other primary xylem rib in each whorl, with intervening ribs producing traces in whorls above and below. Second‐order branches have only ultimate appendages that are attached in a nonwhorled, three‐dimensional, or alternate arrangement. Sterile ultimate appendages dichotomize up to six times and terminate in recurved tips. Fertile ultimate appendages have paired sporangia distally; these sporangia are often upright but are otherwise similar to sterile examples. The stelar anatomy demonstrates an iridopteridalean affinity for these plants, resembling Arachnoxylon kopfii Read in arrangement and number of xylem ribs although it is smaller in size. Among iridopteridaleans, the branching pattern and mode of trace departure is unique, and we therefore name the plant Compsocradus laevigatus gen. et sp. nov.

The Anatomy of Rotoxylon dawsonii comb. nov. (Cladoxylon dawsonii) from the Upper Devonian of New York State

Cladoxylon dawsonii (Dawson) Read was reexamined by sectioning and analysis of a portion of Dawson’s original specimen. The primary xylem consists of 18 radially oriented and elongate primary xylem ribs. Toward the center of the system, some xylem ribs are laterally continuous with adjacent ribs, forming elongate xylem segments, whereas others appear discrete. Order of xylem maturation is mesarch, with one to three protoxylem strands located near the tip of each primary xylem rib. Primary phloem immediately surrounds each primary xylem rib and consists of sieve cells. To the outside of the primary phloem, a conspicuous ground tissue is comprised of roughly isodiametric parenchyma with dark contents in their lumina as well as parenchyma cells that are longitudinally elongate with clear lumina. Beyond the vascular column, a fragmentary cortex contains numerous vascular traces embedded in parenchyma. These latter cells are surrounded by conspicuous masses of longitudinally elongate cortical thick‐walled parenchyma. Vascular traces depart from the tips of the primary xylem ribs in a whorled phyllotaxis. Most traces emerge along the midplane of the primary xylem ribs. However, some depart at an oblique angle. This reinvestigation of an Upper Devonian specimen, known since 1882, provides significant new information on stelar architecture, trace departure, tissue histology, and phyllotaxis. Our study indicates systematic placement of the plant within the Iridopteridales and the recognition of a new iridopterid genus, Rotoxylon. New anatomical evidence indicates Rotoxylon is unusual, exhibiting diagnostic traits of both Cladoxylopsida and Iridopteridales, thus challenging current phylogenetic interpretation of both groups.

Evolution of land plant architecture: beyond the telome theory

Abstract For well over 50 years, the telome theory of Walter Zimmermann has been extremely influential in interpreting the evolutionary history of land plant architecture. Using the “telome/ mesome” distinction, and the concept of universal “elementary processes” underlying the change in form in all plants, the theory was an ambitious synthesis based on the proposition that evolutionary change might be understood by a simple set of developmental or evolutionary rules. However, a major problem resides in deciding exactly how assertions of change are to span both developmental and evolutionary domains simultaneously, and, we argue, the theory critically fails testability as a scientific theory. Thus, despite continued popularity for the descriptive terms derived from the theory in evolutionary studies of early land plants, time has come to replace it with a more explicit, testable approach. Presented here is an attempt to clarify perhaps the most important issue raised by the telome theory—whether simple changes in basic developmental processes suffice to describe much of early land plant evolution. Considering the morphology of Silurian–Devonian fossil members, it is hypothesized that early land plants possessed a common set of developmental processes centered on primary growth of shoot apical meristems. Among these were (1) the capacity to monitor and act upon internal physiological status here modeled as “apex strength,” (2) a mechanism for allocation of apex strength in a context-dependent way at each point of branching, (3) a rule for context-dependent apex angle for branches, (4) a largely invariant phyllotaxis unrelated to physiological status, and (5) a simple switch for terminating primary growth, based in part on genetics. Implemented as a set of developmental rules within a simple L-system model, these aspects of primary development in plants determine a sizable range of resultant morphologies, some of which are highly reminiscent of the early fossils. Thus, some support is found, perhaps, for Zimmermanns intuition. However, traditional concepts of growth patterns in plants, including the contrast between epidogenesis and apoxogenesis, require updating. In our reformulation, developmental processes, stated as rules of developmental dynamics, together constitute what we term the plants developmental state. Using a hypothetico-deductive format, one may hypothesize intrinsic (or genetic) developmental processes that play out as realized developmental activity in specific spatial/temporal contexts, as modified by multiple context factors. The resultant plant morphology is highly dependent on multiple and simultaneous pathway ontogenetic trajectories. Within a likely set of developmental rules reasonably inferred from plant development, some of Zimmermanns elementary processes are perhaps recognizable whereas others are not. Progressively “overtopped” morphologies are easily produced by modifying intrinsic branch allocation. However, even so, the other developmental rules have a profound effect on final architectures. Planate architectures and circination vernation, often treated as special cases by plant morphologists, are perhaps better understood in terms of recurrent or iterative developmental relationships. Much analytic work remains before a completely specified system of rules will emerge. A well-articulated relationship between ontogeny and phylogeny remains fundamentally important in assessing evolutionary change. Fossil and living plants make it abundantly clear that current evolutionary concepts involving modification of a single ontogenetic trajectory from ancestor to descendant need to be greatly expanded into consideration of the entire logical geometry of causation in development. A mechanism for testing is also required that need not wait for complete elucidation at the molecular level. The relative simplicity of plant development, combined with an outstanding fossil record of early members, offers unique opportunities along these lines.

The Primary Body of Rellimia thomsonii: Integrated Perspective Based on Organically Connected Specimens

The Blenheim‐Gilboa locality in New York contains Rellimia thomsonii specimens preserved as both compressions and permineralizations that offer an unusually complete perspective on the reproductive structures, primary body, and secondary anatomy of this Middle Devonian plant. Here we describe the vegetative appendages, axis and branch size relationships, and trace departure as well as primary anatomy, including phloem sieve cells of interconnected axis orders of vegetative and fertile specimens. At least five orders are present, and each axis order is approximately half the diameter of the parent axis. Three‐ribbed protosteles are evident in all axes. Protoxylem in transverse section is a continuous three‐ribbed sheet one or two tracheids wide, enveloped by several cell layers of metaxylem in turn surrounded by primary phloem. Sieve cells have vertically arranged sieve areas. Trace departure to axes is similar in vegetative and fertile axes. Traces are apparent proximally as radial elongations of the tip of the parent primary xylem rib. In distal sections, the rib tip is tangentially elongated; ultimately, the trace becomes three‐ribbed. Traces to vegetative appendages and fertile organs divide dichotomously. The new features described here allow us to expand and complement previous work and to discuss our whole‐plant concept of Rellimia.

Unique growth strategy in the Earth's first trees revealed in silicified fossil trunks from China

Significance The evolution of trees and forests in the Mid–Late Devonian Period, 393–359 million years ago, profoundly transformed the terrestrial environment and atmosphere. The oldest fossil trees belong to the Cladoxylopsida. Their water-conducting system is a ring of hundreds of individual strands of xylem (water-conducting cells) that are interconnected in many places. Using anatomically preserved trunks, we show how these trees could grow to a large size by the production of large amounts of soft tissues and new wood around the individual xylem strands and by a controlled structural collapse at the expanding base. We have discovered a complex tree growth strategy unique in Earth history, but with some similarity to that of living palms. Cladoxylopsida included the earliest large trees that formed critical components of globally transformative pioneering forest ecosystems in the Mid- and early Late Devonian (ca. 393–372 Ma). Well-known cladoxylopsid fossils include the up to ∼1-m-diameter sandstone casts known as Eospermatopteris from Middle Devonian strata of New York State. Cladoxylopsid trunk structure comprised a more-or-less distinct cylinder of numerous separate cauline xylem strands connected internally with a network of medullary xylem strands and, near the base, externally with downward-growing roots, all embedded within parenchyma. However, the means by which this complex vascular system was able to grow to a large diameter is unknown. We demonstrate—based on exceptional, up to ∼70-cm-diameter silicified fossil trunks with extensive preservation of cellular anatomy from the early Late Devonian (Frasnian, ca. 374 Ma) of Xinjiang, China—that trunk expansion is associated with a cylindrical zone of diffuse secondary growth within ground and cortical parenchyma and with production of a large amount of wood containing both rays and growth increments concentrically around individual xylem strands by normal cambia. The xylem system accommodates expansion by tearing of individual strand interconnections during secondary development. This mode of growth seems indeterminate, capable of producing trees of large size and, despite some unique features, invites comparison with secondary development in some living monocots. Understanding the structure and growth of cladoxylopsids informs analysis of canopy competition within early forests with the potential to drive global processes.

EPR imaging of vascular changes in oxygen in response to carbogen breathing.

EPR (Electron Paramagnetic Resonance) spectroscopy is being used for in vivo imaging with the recent availability of non-toxic paramagnetic spin probes. The EPR spectral line widths of these agents are directly dependent on oxygen levels. The narrow line width and the long in vivo half-lives make these agents suitable to obtain high resolution spatial images. In this study, the effects of changes in the venous and arterial oxygen in response to changes in oxygen content in the breathing atmosphere is evaluated.

Panorama Image Construction Using Multiple-Photos Stitching from Biological Data

This paper presents an image construction tool for biological image visualization and education using image matching and stitching approaches. The image matching technique is based on the algorithm SURF (Speeded-up Robust Feature) [3, 4], a successor to the popular feature detection algorithm SIFT (Scale Invariant Feature Transform) [1, 2]. Unlike a traditional image stitching approach, our tool assumes that biological images are taken on a linear model with similar degrees of overlap and orientation angle towards ground from air. With these aspects in mind, generated panoramas will display less distortion and more raw valuable details. Such a tool will facilitate the scientific research and education through applications of visual information processing in fields of Biology, Astronomy, Geology, etc.