Ancestral xerophobia: a hypothesis on the whole plant ecophysiology of early angiosperms

Today, angiosperms are fundamental players in the diversity and biogeochemical functioning of the planet. Yet despite the omnipresence of angiosperms in today's ecosystems, the basic evolutionary understanding of how the earliest angiosperms functioned remains unknown. Here we synthesize ecophysiological, paleobotanical, paleoecological, and phylogenetic lines of evidence about early angiosperms and their environments. In doing so, we arrive at a hypothesis that early angiosperms evolved in evermoist tropical terrestrial habitats, where three of their emblematic innovations – including net-veined leaves, xylem vessels, and flowers – found ecophysiological advantages. However, the adaptation of early angiosperm ecophysiology to wet habitats did not initially promote massive diversification and ecological dominance. Instead, wet habitats were permissive for the ecological roothold of the clade, a critical phase of early diversification that entailed experimentation with a range of functional innovations in the leaves, wood, and flowers. Later, our results suggest that some of these innovations were co-opted gradually for new roles in the evolution of greater productivity and drought tolerance, which are characteristics seen across the vast majority of derived and ecologically dominant angiosperms today

Coherent and spontaneous Raman spectroscopy in shocked and unshocked liquids

Coherent and non-coherent Raman spectroscopy is being used to study the structure and energy transfer in molecular liquids at high pressures. Stimulated Raman scattering, coherent anti-Stokes Raman scattering, and Raman induced Kerr effect scattering measurements have been performed in liquid benzene and liquid nitromethane shocked to pressures up to 11 GPa. Frequency shifts were observed for the 992 cm/sup -1/ ring stretching mode of benzene and the 920 cm/sup -1/ CN stretching mode of nitromethane. Results of these dynamic experiments are compared to spontaneous Raman scattering measurements made in a high temperature diamond anvil cell. Also, a picosecond infrared pump/spontaneous anti-Strokes Raman probe experiment is being used to measure CH stretch vibrational relaxation times in liquid halogenated methanes statically compressed to a few tenths GPa. 87 refs., 17 figs

Human placental villi contain stromal macrovesicles associated with networks of stellate cells

Placental function is essential for fetal development and establishing the foundations for lifelong health. The placental villous stroma is a connective tissue layer that supports the fetal capillaries and villous trophoblast. All the nutrients that cross the placenta must also cross the stroma, and yet little is known about this region. This study uses high-resolution three-dimensional imaging to explore the structural complexity of this region within the placental villi. Serial block-face scanning electron microscopy and confocal microscopy were used to image the placental villous stroma in three-dimensions. Transmission electron microscopy (TEM) was used to generate high resolution two-dimensional images. Stereological approaches were used to quantify volumes of stromal constituents. Three-dimensional imaging identified stromal extracellular vesicles, which constituted 3.9% of the villous stromal volume. These stromal extracellular vesicles were ovoid in shape, had a median length of 2750 nm (range 350-7730 nm) and TEM imaging confirmed that they were bounded by a lipid bilayer. Fifty-nine per cent of extracellular vesicles were in contact with a fibroblast-like stellate cell and these vesicles were significantly larger than those where no contact was observed. These stellate cells formed local networks with adherent junctions observed at contact points. This study demonstrates that the villous stroma contains extracellular macrovesicles which are considerably larger than any previously described in tissue or plasma. The size and abundance of these macrovesicles in the villous stroma highlight the diversity of extracellular vesicle biology and their roles within connective tissues.</p