51 research outputs found

    Ecological and biological features of Triglochin maritima L. in the biotopes of the littoral zone with different degree of flooding on the coast of the White Sea

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    The study of Triglochin maritima L. was carried out on the Pomor (western) coast of the White Sea, in the Republic of Karelia (64°22'81"N, 35°93'14"E). Morphological analysis of aboveground and underground parts of the clones was performed on virginal plants. Anatomical analysis of leaf sheaths of the current year shoots, rhizomes and adventitious roots was carried out. The viability of pollen was assessed by determining the relative share of normally developed and malformed pollen grains. The content of heavy metals was determined in the soil, sea water and plant samples. The study was carried out on a model transect in the littoral zone on three test plots representing the lower littoral; the middle and the upper littoral zones. Adaptation to wave and storm impact was manifested in a well-developed system of underground organs. In the lower littoral, underground part surpasses the aboveground vegetative organs in terms of the mass and the formation of mechanical tissues. This allows the plants to anchor stronger in the substrate. Pollen analysis confirmed the adaptability of T. maritima plants to the conditions of the lower littoral by a high percentage of normal and, consequently, fertile pollen, which ensures sexual reproduction of the species. T. maritima can be considered as a Fe hyperaccumulator as the plant accumulates very high levels of Fe (22–34 g kg-1), especially in the lower and middle littoral zones, both in underground and aboveground organs. The ability of T. maritima plants to actively deposit metals was revealed on the basis of the coefficient of biological absorption of metals and makes it possible to suggest potential possibility of using the species in phytoremediation technologies on coastal territories

    The status of Habitats Directive Annex I saltmarsh habitats, transition zones and spartina species in England

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    On unmodified soft sediment coastlines, of which there are long lengths especially on the English east and south coasts, there should be a wide transitional zone between tidal areas and full terrestrial land. The conditions in this zone result in a rich and distinctive range of habitats. There are two saltmarsh habitats listed in Annex I of the Habitats Directive within this zone (H1420 Mediterranean and thermo-Atlantic halophilous scrubs and H1320 Spartina swards,Spartinion maritimae) reflecting its importance for nature conservation. At the time work for this project was started in 2012, the conservation status of these habitats was reported as ‘unfavourable, bad and deteriorating’. Due to construction of artificial sea defences, these zones are now much reduced in extent and distribution and are under threat from a range of factors. This project aims to provide an inventory and description of Annex I saltmarsh habitats and transitional vegetation in England. This will help to update future reporting on conservation status. The outcomes will also help improve understanding of the underpinning processes which can be used in design to improve the potential for recreating these elements of saltmarshes as part of intertidal restoration schemes. The project also provides an up to date assessment of Spartina alterniflora stands in the Solent SAC through review and field survey for 2012

    Restoration genetics of north-west European saltmarshes: A multi-scale analysis of population genetic structure in Puccinellia maritima and Triglochin maritima

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    Increasing human pressure combined with sea level rise and increased storminess is threatening coastal ecosystems around the world. Among these ecosystems, saltmarshes are particularly endangered due to their position in temperate areas with low wave action where human density is often high (e.g. estuaries). Around the UK, centuries of land reclamation have led to a substantial decrease of the area of saltmarsh. Over the past decades, restoration schemes have been implemented in numerous coastal locations in an attempt to counteract this loss. Such schemes involve allowing sea water to inundate a previously embanked area and letting the vegetation develop naturally, thereby reverting to saltmarsh through natural colonisation. However, surveys of restored areas that have looked at the recovery of plant species diversity or functional characteristics often show that restored saltmarshes do not reach the state of a natural saltmarsh ecosystem. While there is much data at the species level, recovery of plant intra-specific diversity (genetic diversity) has not been assessed in restored saltmarsh although this component of biodiversity is receiving increasing attention for its effect on ecosystem function. This thesis represents the first attempt to (1) characterize the nation-wide genetic structure of two important north-west European saltmarsh plant species, the common saltmarsh grass (Puccinellia maritima) and the sea arrowgrass (Triglochin maritima) and (2) compare levels of genetic diversity and structure between restored and natural ecosystems. Microsatellite molecular markers were developed for both species. Using innovative methods to analyse the genetic data obtained for these two polyploid species, this thesis highlights that genetic diversity at the national scale is organised regionally for both species, although gene-flow is still restricted between populations within the same region. Gene-flow between populations is determined by different processes depending on the species. While coastal processes mainly influence gene dispersal in P. maritima, overland routes of dispersal are involved for T. maritima. These differences are believed to be due to differences in dispersal ecology between the two species. Although gene-flow exists between distant saltmarshes, the genetic analysis of P. maritima and T. maritima colonists arriving on restored sites highlighted their local origin and reaffirmed that it is preferable to restore saltmarsh where a nearby natural saltmarsh can act as a source of colonists. A multiple paired-site comparison identified similar genetic diversity between restored and natural saltmarshes indicating that restoration of local genetic diversity is rapid for both species. A single site comparison at Skinflats in the Forth estuary compared fine-scale spatial genetic structure between the restored and natural saltmarsh. Interestingly, no structure was detected for T. maritima either in restored or natural saltmarsh. In contrast, a strong genetic structure organised along the elevation gradient was observed in the natural saltmarsh for P. maritima but was absent in the restored saltmarsh. The origin of this structure is not clear but could be due to restricted gene-flow between individuals from different elevations due to strong post-zygotic selection, as suggested in previous work. In any case, this lack of structure in the restored saltmarsh indicates that genetic recovery is incomplete in this respect for P. maritima. This thesis introduces the growing field of restoration genetics to saltmarsh ecology and identifies the principal population genetic trends in two of the species dominating the vegetation of north-west European saltmarshes community. The information given here will be useful for restoration practitioners and provides a strong foundation for future work characterizing the importance of genetic diversity for saltmarsh function

    Salt tolerance of halophytes, research questions reviewed in the perspective of saline agriculture

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    Halophytes of the lower coastal salt marsh show increased salt tolerance, and under high salinity they grow faster than upper marsh species. We could not show reduced growth rate of halophytes compared with glycophytes when grown under non-saline conditions. This indicates limited energy costs associated with high-salt tolerance in plants of genera such as Salicornia, providing a good perspective of saline agriculture cultivating Salicornia as a vegetable crop.We show that halophytes do not occur on non-saline or inland sites because of a reduced growth rate at low soil salinity, but probably due to other ecological traits of glycophytic upper marsh species. These traits provide competitive advantage over lower salt marsh halophytes, such as earlier germination and increased growing season length.Some halophytic Amaranthaceae (Salicornioideae, Chenopodioideae and Suaedoideae) are not just highly salt tolerant, their growth rate is stimulated at a salinity range of 150–300 mM NaCl. Alternatively this may be described as depressed growth at low salinity.Selective pressure for such high-salt tolerance and salt stimulated growth likely occurred with prevailing arid climate and saline soil conditions. Under such conditions highly-salt tolerant succulent Salicornioideae, Chenopodioidea and Suaedoideae may have evolved about 65 Mya. In the context of evolution and diversication of land plants this origin of highly-salt tolerant succulent plants is relatively recent.Such high-salt tolerance might be characterized as constitutive in comparison with inducible (lower) salt tolerance of other dicotyledonae and monocotyledonae (Poaceae) species. Levels of salt tolerance of the latter type span a large range of low, intermediate to high-salt tolerance, but do not include salt stimulated growth. Salt tolerant traits of the latter inducible type appear to have evolved repeatedly and independently.Early highly-salt tolerant succulent Salicornioideae, Chenopodioidea and Suaedoideae were perennial and frost sensitive and occurred in warm temperate and Mediterranean regions. A shift from the perennial Sarcocornia to an annual life form has been phylogenetically dated circa 9.4–4.2 Mya and enabled evolution of annual hygrohalophytes in more northern coastal locations up to boreal and subarctic coastal sites avoiding damage of winter frost. Diversification of such hygrohalophytes was facilitated by polyploidization (e.g. occurrence of tetraploid and diploid Salicornia species), and a high degree of inbreeding allowing sympatric occurrence of Salicornia species in coastal salt marshes.High-level salt tolerance is probably a very complex polygenic trait. It is unlikely that glycophytes would accommodate the appropriate allelic variants at all the loci involved in halophyte salt tolerance. This might explain why attempts to improve crop salt tolerance through conventional breeding and selection have been unsuccessful to date.Genetic engineering provides a viable alternative, but the choice for the appropriate transgenes is hampered by a fundamental lack of knowledge of the mechanisms of salt tolerance in halophytes. The chances to identify the determinant genes through QTL analyses, or comparisons among near isogenic lines (NILS) are limited. Salt-tolerance is usually a species-wide trait in halophytes, and intra-specific divergence in salt tolerance in facultative halophytes seems to be often associated with chromosomal incompatibility.A variety of candidate salt tolerance genes been identified in Arabidopsis thaliana, among which genes encoding Na+ and K+ transporters, and genes involved in the general stress or anti-oxidant response, or in compatible solute metabolism. Many of these genes have been over-expressed in different glycophytic hosts, which usually appeared to alleviate, to some degree, the response to high salinity levels. However, with few exceptions, there are no indications that the same genes would be responsible for the superior salt tolerance in (eu)halophytes. Comparisons of gene expression and gene promoter activity patterns between halophytes and glycophytes are, with few exceptions, virtually lacking, which is a major omission in current day salt tolerance research.Full-genome transcriptomic comparisons between halophytes and related glycophytes through deep sequencing seem to be the most promising strategy to identify candidate genetic determinants of the difference in salt tolerance between halophytes and glycophytes.The most reliable validation of any candidate gene is through silencing the gene in the halophytic genetic background, preferably down to the level at which it is expressed in the glycophyte reference species. This requires genetically accessible halophyte models, which are not available to date, with the exception of Thellungiella halophila. However, more models are required, particularly because T. halophila is not a typical halophyte. Eventually, the pyramiding of validated salt tolerance genes under suitable promoters may be expected to be a viable strategy for crop salt tolerance improvement

    Investigating the Role Of Elevated Salinity in the Recession of a Large Brackish Marsh in the Fraser River Estuary

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    At least 160 ha of the Sturgeon Bank low marsh in the Fraser River delta died off between 1989 and 2011. Humans have heavily modified the Fraser River estuary since the late 1800’s, including installing a series of jetties throughout the leading edge of the delta to train the course of the river. I established a reciprocal transplant experiment to determine the role of elevated salinity in the marsh recession and generate information needed to eventually revegetate areas of receded marsh as part of an intergovernmental collaboration to investigate the causes of this marsh recession. I propose specific actions to better monitor, maintain, and restore the Fraser River delta foreshore brackish marshes in response to ongoing ecological degradation of the estuary. The predicted effects of climate change and sea-level rise may cause us to rethink options for restoring the Sturgeon Bank marsh. &nbsp

    Sustainable use of mangroves as sources of valuable medicinal compounds: Species identification, propagation and secondary metabolite composition

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    Mangroves are able to withstand a number of stress factors, such as high salt concentrations, tidal flooding, strong wind, solar radiation and heat. Their ability to grow under these circumstances is based on morphological and physiological adaptations, among them the high abundance of plant secondary metabolites. We are interested to investigate and exploit their medicinal and biotechnological potential for new bioactive compounds, without collecting material in the countries of origin and in a sustainable way. Therefore, a simple identification system based on molecular marker analysis, and a sustainable greenhouse propagation protocol for the continuous supply of fresh plant material, were established. DNA barcoding of the internal transcribed spacer (ITS) including ITS1, the 5.8S rRNA region and ITS2 as a molecular marker was applied for several mangrove species. The obtained data and GenBank sequences were used for species identification. Three mangrove species are cultivated in our greenhouse and propagated in different ways: Avicennia species produced many propagules in the greenhouse, however, further propagation by cuttings was not successful. Laguncularia racemosa was propagated by cuttings in a fog house whereas Bruguiera cylindrica was difficult to cultivate and propagation was not successful. Finally, the concentration of secondary phenolic compounds, including flavonoids, and the content of major elements were compared among naturally and greenhouse-grown mangroves indicating comparable amounts and composition
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