Opportunistic Germination Behaviour of Gypsophila (Caryophyllaceae) in Two Priority Habitats from Semi-arid Mediterranean Steppes
Gypsophila tomentosa and G. struthium are closely related species, characteristic of two European priority habitats, salt and gypsum inland steppes, respectively. Germination strategies of the two taxa were investigated in plants from two nearby populations, growing under the same climatic conditions but on different types of soil, and belonging to different plant communities. Their germination patterns were studied at five constant temperatures in darkness: 5oC, 10oC, 15oC, 20oC and 25oC, and the base temperature and the thermal time requirement were calculated. As the distribution area of both species is subjected to a Mediterranean continental climate with significant differences between…
Responses to salt stress in the halophyte Plantago crassifolia (Plantaginaceae)
Abstract General responses to salt stress have been investigated in the halophyte Plantago crassifolia. Seed germination was strongly inhibited by NaCl, although seed viability and germination capacity were not affected by salt pre-treatments. A concentration-dependent inhibition of plant growth was observed in the presence of NaCl, which was accompanied by the accumulation of Na+ ions in the leaves, as determined by cation exchange HPLC. A 20-fold increase of proline content in leaves was observed when plants were treated with 500 m m NaCl, suggesting a protective role against high salinity stress for this amino acid, whose possible mechanism of action is discussed.
Native-Invasive Plants vs. Halophytes in Mediterranean Salt Marshes: Stress Tolerance Mechanisms in Two Related Species
Dittrichia viscosa is a Mediterranean ruderal species that over the last decades has expanded into new habitats, including coastal salt marshes, ecosystems that are per se fragile and threatened by human activities. To assess the potential risk that this native-invasive species represents for the genuine salt marsh vegetation, we compared its distribution with that of Inula crithmoides, a taxonomically related halophyte, in three salt marshes located in “La Albufera” Natural Park, near the city of Valencia (East Spain). The presence of D. viscosa was restricted to areas of low and moderate salinity, while I. crithmoides was also present in the most saline zones of the salt marshes. Analyses…
Characterizing the effects of salt stress in Calendula officinalis L
In this study the effects of salt stress on growth and several stress markers were investigated in the ornamental and medicinal plant Calendula officinalis. One month old plants were submitted to increasing concentrations of salt up to 150mM NaCl for a period of 30 days. Salinity affected growth in terms of stem length and fresh weight of the plants, but water content remained unchanged indicating a certain tolerance to low and mild concentrations of salt. Although Na+ and Cl− increased in parallel to applied salt treatments, the levels of K+ and Ca2+ showed no significant change, while Mg2+ levels recorded a two folds increase upon the application of the highest salt concentration. Other m…
Genetic variability in the endemic Leucojum valentinum
The genetic variability of Leucojum valentinum Pau (Amaryllidaceae), a vulnerable endemic species restricted to a small area in the region of Valencia (Eastern Spain), has been studied using random amplified polymorphic DNA (RAPD) markers. A total of 197 individuals from eleven populations were studied using 13 RAPD primers. Our results show high variability for the species, low differentiation among populations and uncorrelated levels of genetic variability and population size. Four groups in which three populations (SAG, PUG and COL) are separated from all the others were found, but without connection to geographical location.
Effects of salt stress on the reproductive biology of the halophyte Plantago crassifolia
Floral phenology, pollen quality and seed set of Plantago crassifolia plants, grown in the presence of increasing NaCl concentrations, were studied to test how this Mediterranean halophyte responded to salt stress during the reproductive phase of its life cycle. "Reproductive success" was maximal in plants grown in non-saline conditions, or in the presence of 100 mM NaCl, but it was negatively affected by higher salinities, due to a progressive reduction of pollen fertility, seed set, and seed viability.
Unraveling Salt Tolerance in Halophytes: A Comparative Study on Four Mediterranean Limonium Species with Different Geographic Distribution Patterns
[EN] We have performed an extensive study on the responses to salt stress in four related Limonium halophytes with different geographic distribution patterns, during seed germination and early vegetative growth. The aims of the work were twofold: to establish the basis for the different chorology of these species, and to identify relevant mechanisms of salt tolerance dependent on the control of ion transport and osmolyte accumulation. Seeds were germinated in vitro, in the presence of increasing NaCl concentrations, and subjected to ¿recovery of germination¿ tests; germination percentages and velocity were determined to establish the relative tolerance and competitiveness of the four Limoni…
Financial constraints and R&D and exporting strategies for Spanish manufacturing firms
We investigate the role of internal and external financial constraints in the firms� joint decision to export and invest in R&D. We use objective measures at the firm level such as cash flow and financial costs. We further analyze both if firms� size and the onset of the current economic crisis have had an impact. We estimate our model with Spanish manufacturing firms for the period 1990�2011, and obtain that both internal and external financial constraints are relevant.
Nuclear DNA content variation inHalimiumandXolantha(Cistaceae)
Abstract Chromosome numbers and nuclear DNA contents were determined in several taxa of two genera of Cistaceae, Halimium and Xolantha. The diploid chromosome number 2n = 18 is stable within the genus Halimium. In Xolantha, the diploid chromosome number 2n = 14 was confirmed in X. tuberaria, and hexaploid (2n = 36) and octoploid (2n = 48) cytotypes were found in X. guttata. DNA amounts, first reported here for these genera, were determined by flow cytometry of propidium iodide-stained nuclei. Within Halimium there is a more than twofold difference in genome size between H. calycinum (7.61 pg DNA) and H. atriplicifolium (3.66 pg DNA). Within the genus Xolantha, absolute genome sizes of 7.3 a…