72 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
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]
Climate warming could increase recruitment success in glacier foreland plants
No full textBackground and Aims: Glacier foreland plants are highly threatened by global warming. Regeneration from seeds on deglaciated terrain will be crucial for successful migration and survival of these species, and hence a better understanding of the impacts of climate change on seedling recruitment is urgently needed to predict future plant persistence in these environments. This study presents the first field evidence of the impact of climate change on recruitment success of glacier foreland plants. • Methods: Seeds of eight foreland species were sown on a foreland site at 2500m a.s.l., and at a site 400m lower in altitude to simulate a 2·7 °C increase in mean annual temperature. Soil from the site of origin was used to reproduce the natural germination substrate. Recruitment success, temperature and water potential were monitored for 2 years. The response of seed germination to warming was further investigated in the laboratory. • Key Results: At the glacier foreland site, seedling emergence was low (0 to approx. 40 %) and occurred in summer in all species after seeds had experienced autumn and winter seasons. However, at the warmer site there was a shift from summer to autumn emergence in two species and a significant increase of summer emergence (13-35 % higher) in all species except two. Survival and establishment was possible for 60-75 % of autumn-emerged seedlings and was generally greater under warmer conditions. Early snowmelt in spring caused the main ecological factors enhancing the recruitment success. • Conclusions: The results suggest that warming will influence the recruitment of glacier foreland species primarily via the extension of the snow-free period in spring, which increases seedling establishment and results in a greater resistance to summer drought and winter extremes. The changes in recruitment success observed here imply that range shifts or changes in abundance are possible in a future warmer climate, but overall success may be dependent on interactions with shifts in other components of the plant community
The ‘pure’ relationship, sham marriages and immigration control
No full textThis is the author pre-print version. The final version is available from Hart Publishing via the link in this record.This chapter investigates the circumstances in which a marriage involving a non- EEA migrant spouse is designated a sham marriage so that residence rights are refused. It analyses the problems of understanding and defining a sham marriage and argues that controls over sham marriages often regulate a much wider range of marriages than those entered for the sole purpose of obtaining residence rights
Legal Rationality and Family Property
No full textThis author version was accepted for publication by Hart Publishing and has been submitted in line with the publisher's self archiving.Family law, in so far as it is trying to regulate disputes relating to money and property on relationship breakdown, has its work cut out. For it is trying to deal in a rational way with issues between people who are in an emotionally charged relationship situation and where most might predict that rationality is unlikely to prevail (Beck and Beck-Gernsheim, 1995). Whilst some, such as John Dewar, see the answer as conceding to what he terms ‘the normal chaos of family law’ which nonetheless works on a practical level due to the pragmatic solutions of professionals operating within a discretionary legal framework (Dewar, 1998), others have argued that this is not the optimal way forward for family law in general (Henaghan, 2008) and the regulation of new family forms in particular (Barlow et al, 2005). This chapter will therefore consider whether family law can avoid the trap of a ‘rationality mistake’ – whereby legislators overestimate the law’s ability to steer behaviour in a particular direction (Barlow and Duncan, 2000; Barlow et al, 2005) – yet still develop a coherent theory of family law to apply in this field (Eekelaar, 2006; Henaghan, 2008). It has been argued convincingly by critical theorists that family law ‘needs to be socially located’ (see eg Freeman, 1985: 153–54). Given shifting attitudes and more complex married and unmarried families resulting from changed parenting, partnering, and repartnering patterns and behaviours, this presents a real challenge. In rising to this, it will be argued by drawing on empirical research that it is now time to take stock of both the emotional and economic foundations and commitment on which modern couple relationships are built in order to consider how family law should weigh the competing values of promoting personal financial autonomy yet providing legal protection for the economically weaker partner on
relationship breakdown. Arguably this has already been done in the cohabitation context by the Law Commission in its consideration of proposals for the reform of cohabitation law (Law Commission, 2007). But has the right balance been struck here? Is the current legal hierarchy still fit for purpose or are we drawing the regulatory lines in the wrong places? These are the questions this chapter aims to pursue. In so doing, it will draw on empirical research to examine whether family law in this area can find a way to cope with its chaotic raw material, avoid the legal rationality mistake yet become sufficiently coherent to provide satisfactory outcomes for those it serves
Parental effects modulate seed longevity: Exploring parental and offspring phenotypes to elucidate pre-zygotic environmental influences
No full textSeed longevity, which is essential for germplasm conservation and survival of many land plant species, can vary considerably within species and cultivars. Here, we explore the relationship between parental and offspring phenotypes to elucidate how pre-zygotic environment affects seed longevity
Unusual case of difficult double-lumen endotracheal tube removal
No full textA reusable Robertshaw red rubber double-lumen endotracheal tube (DLT) was placed to facilitate lung isolation for thoracoscopy in a 49-year-old atopic patient. In spite of its smooth insertion, it was then not possible to remove the DLT. Direct laryngoscopy showed severe laryngeal edema. After 48 hours of medical treatment with steroids, the trachea was extubated. The laryngeal edema could have been the result of physical and chemical irritation by the reusable rubber DLT itself, or from the substances formed during repeated cleaning and sterilization of the DLT. Atopic patients who are prone to developing latex allergy are also more liable to develop severe reactions to chemical, mechanical, and physical irritation from reusable red rubber DLTs or from the chemical solution used for its cleaning and sterilization. © 2009 Elsevier Inc. All rights reserved.Adhikary Sanjib Das, 2006, Anesth Analg, V103, P1594, DOI 10.1213-01.ane.0000247028.20845.be; AKERS JA, 1990, ANAESTH INTENS CARE, V18, P577; Burkle CM, 2006, ANESTH ANALG, V102, P322, DOI 10.1213-01.ANE.0000181319.70639.3B; Dark A, 1999, BRIT J ANAESTH, V82, P644; DORSCH JA, 1979, UNDERSTANDING ANESTH, P282; DRYDEN GE, 1977, ANESTH ANALG, V56, P451; Guess W L, 1970, Int Anesthesiol Clin, V8, P815, DOI 10.1097-00004311-197000840-00007; Ho LI, 1996, INTENS CARE MED, V22, P933; Langeron O, 2006, CRIT CARE, V10, DOI 10.1186-cc5112; LEVY JH, 2001, CLIN ANESTH, P1297; NIEHAUS HH, 1995, HNO, V43, P446; Probert DJ, 2003, ANAESTH INTENS CARE, V31, P584; STETSON JB, 1970, ANESTHESIOLOGY, V33, P635, DOI 10.1097-00000542-197012000-0001311
Pre-zygotic parental environment modulates seed longevity
No full textThe potential for the pre-zygotic plant growth environment to play a role in determining seed longevity was investigated for a species that inhabits arid to semi-arid Australia. Seed longevity is particularly important for wild populations in fluctuating environments because the longer a seed-lot is able to survive in the soil seed bank the more likely it is to buffer the population from unpredictable environments. Thus Wahlenbergia tumidifructa plants received wet or dry soil moisture within a warm or cool glasshouse until flowering. Seeds subsequently produced by flowers that opened on the day that plants were moved to a common environment were collected at maturity and longevity assessed by controlled ageing at 60% relative humidity and 45 degrees C. Mean seed longevity was similar for seeds produced by plants that grew in warm-wet, warm-dry and cool-dry conditions (P(50) of about 20 days), but extended for plants in cool-wet conditions (P(50) = 41.7 days). Cool temperatures resulted in seeds with a wider distribution of lifespans (sigma = 20 days) than warm conditions (sigma = 12 days); the large sigma caused the extended P(50) for cool-wet plants, but not cool-dry as a result of a concomitant reduction in initial seed germination (K(i)). After moving to the common environment, all plants generated new vegetative material, which went on to produce seeds with similar longevity (P(50) approx. 20 days) irrespective of original environment. Visible phenotypic responses of the parent to environmental conditions correlated with longevity and quality parameters of the progeny seeds, suggesting that a parental effect modified seed longevity. Our study provides novel empirical data showing that environmental conditions expected under climate change scenarios may potentially cause seed longevity to decline for a species that inhabits arid to semi-arid Australia. These negative impacts on population buffering may weaken the storage effect mechanism of species coexistence in fluctuating environments
Effects of Light, Scarification, and Gibberellic Acid on Seed Germination of Eight Pedicularis Species from Yunnan, China
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