1,219 research outputs found
Comparative seed dormancy and germination of eight annual species of ephemeral wetland vegetation in a Mediterranean climate
No full textEphemeral wetland vegetation (EWV) in the Mediterranean Basin appears in temporary wetlands where favourable hydrological conditions exist only for a short time and year-to-year variability is high. Here, we report results of the seed germination, dormancy and desiccation tolerance of eight annual species living in this vulnerable habitat. Experiments were performed in laboratory conditions under constant and alternating temperatures and using a 12-h daily photoperiod or continuous darkness. Whilst germination and dormancy differed between the species, seeds demonstrated an absolute light requirement and prefer cool temperatures to germinate (mean a parts per thousand currency sign15 A degrees C). Logistic regression analysis showed significant effects of alternating temperature in all the species except in Tillaea vaillantii whose germination was stimulated by constant temperature. Mean temperature was a significant term in the logistic models for the dormant species Cicendia filiformis, Linum radiola and T. vaillantii for which after-ripening was an effective dormancy-breaking treatment. From these results we infer three strategies of regeneration by seeds: (1) species germinating during the whole vegetative season (2) species germinating in a narrow temperature niche and (3) species requiring flooding (T. vaillantii). Seeds possessed orthodox storage behaviour (tolerating drying to 15 % relative humidity) and may be amenable to seed banking as a means of ex-situ conservation. We conclude that EWV species are adapted to the irregular presence of water with characteristics that are typical of neither truly aquatic nor wetland plants. These EWV species showed a more plastic germination response based on alternating and constant temperature sensitivity and a low proportion of dormant seeds
Seeds of alpine plants are short lived: implications for long-term conservation
No full textBackground and Aims: Alpine plants are considered one of the groups of species most sensitive to the direct and indirect threats to ecosystems caused by land use and climate change. Collecting and banking seeds of plant species is recognized as an effective tool for providing propagating material to re-establish wild plant populations and for habitat repair. However, seeds from cold wet environments have been shown to be relatively short lived in storage, and therefore successful long-term seed conservation for alpine plants may be difficult. Here, the life spans of 69 seed lots representing 63 related species from alpine and lowland locations from northern Italy are compared. •Methods Seeds were placed into experimental storage at 45°C and 60 relative humidity (RH) and regularly sampled for germination. The time taken in storage for viability to fall to 50 (p50) was determined using probit analysis and used as a measure of relative seed longevity between seed lots. •Key Results Across species, p50 at 45°C and 60 RH varied from 4·7 to 95·5 d. Seed lots from alpine populations/species had significantly lower p50 values compared with those from lowland populations/species; the lowland seed lots showed a slower rate of loss of germinability, higher initial seed viability, or both. Seeds were progressively longer lived with increased temperature and decreased rainfall at the collecting site. •Conclusions Seeds of alpine plants are short lived in storage compared with those from lowland populations/related taxa. The lower resistance to ageing in seeds of alpine plants may arise from low selection pressure for seed resistance to ageing and/or damage incurred during seed development due to the cool wet conditions of the alpine climate. Long-term seed conservation of several alpine species using conventional seed banking methods will be problematic
Author Robin Silbergleid reads from her memoir "Texas girl," and her soon to be published book of poetry, "The baby book" at the Michigan Writers Series
No full textAuthor Robin Silbergleid reads from her memoir "Texas girl," and her soon to be published book of poetry, "The Baby Book." Introductory remarks are provided by MSU Professor Telaina Eriksen and MSU Librarian Michael Rodriguez. Part of the MSU Libraries' Michigan Writers Series. Held at the MSU Main Library and sponsored by the MSU Department of English and the Center for Gender in Global Context
Enigmas
No full textArising from the 2020 Darwin College Lectures, this book presents eight essays from prominent public intellectuals on the theme of Enigmas. Each author examines this theme through the lens of their own particular area of expertise, together constituting an illuminating and diverse interdisciplinary volume. Enigmas features contributions by professor of physics Sean M. Carroll, author Jo Marchant, writer and broadcaster Adam Rutherford, professor of earth sciences Tamsin A. Mather, professor of the history of the book Erik Kwakkel, reader in cultural history Tiffany Watt Smith, mathematician and public speaker James Grime, assistant professor of positive AI J. Derek Lomas, and explorer Albert Y.- M. Lin. This volume will appeal to anyone fascinated by puzzles and mysteries, solved and unsolved
Environmentally induced transgenerational changes in seed longevity: Maternal and genetic influence
No full textBackground and Aims: Seed longevity, a fundamental plant trait for ex situ conservation and persistence in the soil of many species, varies across populations and generations that experience different climates. This study investigates the extent to which differences in seed longevity are due to genetic differences and/or modified by adaptive responses to environmental changes. Methods: Seeds of two wild populations of Silene vulgaris from alpine (wA) and lowland (wL) locations and seeds originating from their cultivation in a lowland common garden for two generations (cA1, cL1, cA2 and cL2) were exposed to controlled ageing at 45 °C, 60 % relative humidity and regularly sampled for germination and relative mRNA quantification (SvHSP17.4 and SvNRPD12). Key Results: The parental plant growth environment affected the longevity of seeds with high plasticity. Seeds of wL were significantly longer lived than those of wA. However, when alpine plants were grown in the common garden, longevity doubled for the first generation of seeds produced (cA1). Conversely, longevity was similar in all lowland seed lots and did not increase in the second generation of seeds produced from alpine plants grown in the common garden (cA2). Analysis of parental effects on mRNA seed provisioning indicated that the accumulation of gene transcripts involved in tolerance to heat stress was highest in wL, cL1 and cL2, followed by cA1, cA2 and wA. Conclusions: Seed longevity has a genetic basis, but may show strong adaptive responses, which are associated with differential accumulation of mRNA via parental effects. Adaptive adjustments of seed longevity due to transgenerational plasticity may play a fundamental role in the survival and persistence of the species in the face of future environmental challenges. The results suggest that regeneration location may have important implications for the conservation of alpine plants held in seed banks. © 2014 The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: [email protected]
Interview of Robin Silbergleid, Michigan State University professor of English and head of the creative writing program, on her broad publishing credits, balancing between an academic career and a writing career, and blurring lines between different genres
No full textAuthor Robin Silbergleid, Michigan State University professor of English and head of the creative writing program, talks about her broad publishing credits and how she balances an academic career with a writing career. She comments on her memoir "Texas girl," suggests that clear genres are going away as lines between them become more blurred, and explains the differences between memoir, autobiography, and the novel. Silbergleid is interviewed by MSU Librarian Michael Rodriguez for the Michigan State University Libraries' Michigan Writers Series. Held in the MSU Main Library
The Robin problem for the Helmholtz equation in a starlike planar domain
No full textThe interior and exterior Robin problems for the Helmholtz equation in starlike planar domains are addressed by using a suitable Fourier-like technique. Attention is in particular focused on normal-polar domains whose boundaries are defined by the so-called “superformula” introduced by J. Gielis. A dedicated numerical procedure based on the computer algebra system Mathematica© is developed in order to validate the proposed approach. In this way, highly accurate approximations of the solution, featuring properties similar to the classical ones, are obtained. The computed results are found to be in good agreement with the theoretical findings on Fourier series expansion presented by L. Carleson.TelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
Cervico-thoracic kyphosis in a girl with Pierre Robin sequence
No full textCongenital cervico-thoracic kyphosis has been encountered in a girl with Pierre Robin sequence. The constellation of the spine malformation complex such as incomplete development of the vertebral bodies associated with defective ossification of the cervico-thoracic pedicles causing effectively the development of complete spinal cord injury at the kyphotic level of C7/T1 were present. Congenital kyphosis secondary to vertebral body hypoplasia has not been reported in connection with Pierre Robin sequence
Round-robin tests of porous disc models
No full textNine research teams organized a round-robin measurement campaign of the wake of two porous discs in a homogeneous and "low-turbulent' flow. Mean streamwise velocity and turbulence intensity profiles at four diameters downstream of the discs were measured and compared through such metrics as the maximum of velocity deficit, the maximum of turbulence intensity, the wake width and the thrust coefficient. The dependence of these metrics on the inflow conditions (freestream turbulence intensity and Reynolds number based on the disc diameter) is discussed.Team Jan-Willem van WingerdenDesign Conceptualization and CommunicationWind Energ
Pulmonary thromboembolism. 1. Current concepts in pathogenesis and diagnosis.
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