70 research outputs found
Ability of Cistus L. shrubs to promote soil rehabilitation in extensive oak woodlands of Mediterranean areas
To assess the ecological function of Cistus salviifolius (CS) and C. ladanifer (CL) shrubs in evergreen oak woodlands, a study was conducted over a 4-year period in southern Portugal. Annual potential return of bio-elements to the soil through litterfall and throughfall, and necromass on soil surface under shrub canopies were assessed along with the dynamics of leaf litter decomposition. Soil bulk density and soil-water retention at different soil matric potential were measured at 0â5 and 5â10 cm depth, and soil chemical properties were determined at 0â5, 5â10, 10â20 and 20â30 cm depth beneath canopies and at barren spaces. Litterfall was higher for CL (4.4â4.6 Mg DM haâ1 yearâ1) than for CS (3.3â3.8 Mg DM haâ1 yearâ1). Annual amount of N returned to the soil through litterfall of CS (22.9 kg N haâ1 yearâ1) was higher than by that of CL (17.2 kg N haâ1 yearâ1), whereas the return of P in CL (4.1 kg P haâ1 yearâ1) was higher than in CS (2.1 kg P haâ1 yearâ1). Leaf decomposition was faster for CS (k= â0.87) than for CL (k=â0.44). N release was also faster for CS than for CL, while that of P was much faster for CL than for CS. Throughfall proportions were 61% of bulk rainfall for CS and 79% for CL. Annual return of Clâ, K+, Ca2+ and Mg2+ by throughfall was more pronounced for CL than for CS. Shrubs improved soil quality, especially in the 0â5 cm top soil layer, by enhancement of organic matter and nutrient content beneath shrub canopies. Therefore, shrubs may promote the invasion of more demanding species, since local areas of high fertility are likely to be favoured sites for vegetation regeneration
Comparison of Biomass and Nutrient Dynamics Between an Invasive and a Native Species in a Mediterranean Saltmarsh
Two saltmarsh species, the native Arthrocnemum
macrostachyum (AM) and the invasive Spartina densiflora
(SD), were compared in terms of monthly variation of
above and belowground biomass, and nutrient (N, P, K, Ca,
Mg, Mn) concentrations, over 1 year, in Castro Marim
saltmarsh, Portugal. Net aboveground primary productivity
was also estimated by two different methods. Above and
belowground biomass were higher in SD than in AM and
there were distinct monthly variations in the two species.
Maximum relative growth rate was observed in the
October/January period for SD (4.92±0.36 mg g-1 day-1)
and in April/July for AM (3.37±1.26 mg g-1 day-1).
Whatever the method used, net aboveground primary
productivity was higher in SD (2,603 and 2,923 g m-2 yr-1,
respectively by the Smalley and the Wiegert and Evans
method) than in AM (692 and 1,012 g m-2 yr-1, respectively).
The turnover rate for aboveground live biomass of AM
was half the value of SD (0.8 yr-1 and 1.7 yr-1,
respectively). The N/P ratio in photosynthetic active
components and belowground biomass of AM (11 and 13)
was higher than in those of SD (7 and 10). Concentrations
of K, Ca and Mg in photosynthetic tissues of SD were
lower than in AM. Differences observed between study
species suggest that S. densiflora has better ability to use
resources and to compete with native species
Plant/Leaf traits and adaptive strategies of Cistus species to Mediterranean drought and insolation in southern Portugal
The effects of climate change can result in dramatic consequences in specific ecosystems such as montados that are seriously threatened by the absence of cork and holm oak (Quercus suber and Q. rotundifolia) natural regeneration. Shrubs of the genus Cistus, which are among the most important elements of encroached montados, seem to promote soil rehabilitation and enhance oak regeneration (SimÔes et al. 2009). In this context, we compared the life strategies and evaluated the potential ability of Cistus species to adapt to the increasing drought expected for the Mediterranean region, and thus their role on the sustainability of cork oak montados
Seed germination of six Iberian endemic species â a contribution to enhance plant conservation
Biodiversity has been degraded all around the world due to anthropogenic factors. To counteract this
worldwide tendency, ecological restoration programs are expanding. In these programs, the use of
native herbaceous species, particularly those endemic or threatened, can be promoted by seeding
them but germination requirements for most of these species are unknown. Our research meant to fill
this gap of information for six Iberian endemic species suitable to use in restoration actions - Digitalis
thapsi, Ferula communis subsp. catalaunica, Linaria amethystea subsp. amethystea, Pterocephalidium
diandrum, Sanguisorba hybrida, and Silene scabriflora subsp. scabriflora. Their seed germination behaviour
was analysed to establish germination protocols for conservation actions. Three germination conditions
were used to simulate different sown seasons. Seeds of all species were tested without pretreatment
and subjected to a cold stratification. Seeds of S. hybrida and P. diandrum were additionally
tested with a scarification treatment. All species reached their better germination performance under
autumn conditions (15/10 C; 8/16 hours). In conclusion, for all the six Iberian endemic species tested,
germination speed and percentage were suitable for their use in native plants reinforcement
Cork oak (Quercus suber L.) seedlings acclimate to elevated
Leaf gas-exchange, leaf and shoot anatomy,
wood density and hydraulic conductivity were investigated in
seedlings of Quercus suber L. grown for 15 months either at
elevated (700 lmol mol-1) or normal (350 lmol mol-1)
ambient atmospheric CO2 concentrations. Plants were
grown in greenhouses in a controlled environment: relative
humidity 50% (±5), temperature similar to external temperature
and natural light conditions. Plants were supplied
with nutrients and two water regimes (WW, well watered;
WS, water stress). After 6 months exposure to CO2
enrichment an increase in photosynthetic rate, a decrease in
stomatal conductance and a decrease in carbon isotope
discrimination (D13C) were observed, along with enhanced
growth and an increase in the number of branches and
branch diameter. Over the same period, the shoot weight
ratio increased, the root weight ratio decreased and the leaf
weight ratio was unaffected. The specific leaf area increased
due to an increase in total leaf thickness, mainly due to the
palisade parenchyma and starch. However, after 9 and
15 months of elevated CO2 exposure, the above-mentioned
physiological and morphological parameters appeared to be
unaffected. Elevated CO2 did not promote changes in vessel
lumen diameter, vessel frequency or wood density in stems
grown in greenhouse conditions. As a consequence, xylem
hydraulic efficiency remained unchanged. Likewise, xylem
vulnerability to embolism was not modified by elevated
CO2. In summary, elevated CO2 had no positive effect on
the ecophysiological parameters or growth of water stressed
plants
Calcium signaling in a low calcium environment: how the intracellular malaria parasite solves the problem
Malaria parasites, Plasmodia, spend most of their asexual life cycle within red blood cells, where they proliferate and mature. The erythrocyte cytoplasm has very low [Ca2+] (<100 nM), which is very different from the extracellular environment encountered by most eukaryotic cells. The absence of extracellular Ca2+ is usually incompatible with normal cell functions and survival. In the present work, we have tested the possibility that Plasmodia overcome the limitation posed by the erythrocyte intracellular environment through the maintenance of a high [Ca2+] within the parasitophorous vacuole (PV), the compartment formed during invasion and within which the parasites grow and divide. Thus, Plasmodia were allowed to invade erythrocytes in the presence of Ca2+ indicator dyes. This allowed selective loading of the Ca2+ probes within the PV. The [Ca2+] within this compartment was found to be âŒ40 ÎŒM, i.e., high enough to be compatible with a normal loading of the Plasmodia intracellular Ca2+ stores, a prerequisite for the use of a Ca2+-based signaling mechanism. We also show that reduction of extracellular [Ca2+] results in a slow depletion of the [Ca2+] within the PV. A transient drop of [Ca2+] in the PV for a period as short as 2 h affects the maturation process of the parasites within the erythrocytes, with a major reduction 48 h later in the percentage of schizonts, the form that re-invades the red blood cells
The influence of meteorological parameters on Alternaria and Cladosporium fungal spore concentrations in Beja (Southern Portugal): preliminary results
Introduction Fungal spores constitute an
important fraction of bioaerosols in the atmosphere.
Objectives To analyse the content of Alternaria and
Cladosporium spores in the atmosphere of Beja and
the effect of meteorological conditions on their
concentrations. Methodology The daily and hourly
data of Alternaria and Cladosporium fungal spores
concentration in the atmosphere of Beja were monitored
from April 12, 2012 to July 30, 2014, based on
the Portuguese Aerobiology Network methodology.
The influence of meteorological conditions on the
studied types of fungal spore concentrations was
assessed through Spearmanâs correlation analysis.
Results During the study period, 20,741 Alternaria
spores and 320,862 Cladosporium spores were
counted. In 2013, there were 5,822 Alternaria spores
and 123,864 Cladosporium spores. The absolute
maximum concentrations of Alternaria and Cladosporium
spores were recorded on November 8, 2013, with
211 and 1301 spores/m3, respectively. Temperature,insolation and wind direction parameters showed a
positive correlation with Alternaria and Cladosporium
spore levels, while relative humidity and precipitation
presented a negative correlation, which is statistically
significant. Wind speed only showed a statistically
significant positive correlation in terms of Alternaria
spore levels. Conclusion Alternaria and Cladosporium
spores are present in the atmospheric air of Beja
throughout the year, with the highest concentration
period occurring during spring and autumn. There was
a clear effect of meteorological parameters on airborne
concentrations of these fungal spores
drug interactions and implications on the ubiquitin/proteasome system
Antimalarial drug resistance remains a major obstacle in malaria control. Evidence from Southeast Asia shows that resistance to artemisinin combination therapy (ACT) is inevitable. Ethnopharmacological studies have confirmed the efficacy of curcumin against Plasmodium spp. Drug interaction assays between curcumin/piperine/chloroquine and curcumin/piperine/artemisinin combinations and the potential of drug treatment to interfere with the ubiquitin proteasome system (UPS) were analyzed. In vivo efficacy of curcumin was studied in BALB/c mice infected with Plasmodium chabaudi clones resistant to chloroquine and artemisinin, and drug interactions were analyzed by isobolograms. Subtherapeutic doses of curcumin, chloroquine, and artemisinin were administered to mice, and mRNA was collected following treatment for RT-PCR analysis of genes encoding deubiquitylating enzymes (DUBs). Curcumin was found be nontoxic in BALB/c mice. The combination of curcumin/chloroquine/piperine reduced parasitemia to 37% seven days after treatment versus the control group's 65%, and an additive interaction was revealed. Curcumin/piperine/artemisinin combination did not show a favorable drug interaction in this murine model of malaria. Treatment of mice with subtherapeutic doses of the drugs resulted in a transient increase in genes encoding DUBs indicating UPS interference. If curcumin is to join the arsenal of available antimalarial drugs, future studies exploring suitable drug partners would be of interest.publishersversionpublishe
Bidirectional Modulation of Alcohol-Associated Memory Reconsolidation through Manipulation of Adrenergic Signaling.
Alcohol addiction is a problem of great societal concern, for which there is scope to improve current treatments. One potential new treatment for alcohol addiction is based on disrupting the reconsolidation of the maladaptive Pavlovian memories that can precipitate relapse to drug-seeking behavior. In alcohol self-administering rats, we investigated the effects of bidirectionally modulating adrenergic signaling on the strength of a Pavlovian cue-alcohol memory, using a behavioral procedure that isolates the specific contribution of one maladaptive Pavlovian memory to relapse, the acquisition of a new alcohol-seeking response for an alcohol-associated conditioned reinforcer. The ÎČ-adrenergic receptor antagonist propranolol, administered in conjunction with memory reactivation, persistently disrupted the memory that underlies the capacity of a previously alcohol-associated cue to act as a conditioned reinforcer. By contrast, enhancement of adrenergic signaling by administration of the adrenergic prodrug dipivefrin at reactivation increased the strength of the cue-alcohol memory and potentiated alcohol seeking. These data demonstrate the importance of adrenergic signaling in alcohol-associated memory reconsolidation, and suggest a pharmacological target for treatments aiming to prevent relapse through the disruption of maladaptive memories.This work was supported by a UK Medical Research Council Programme Grant (G1002231) to BJE and ALM and was conducted in the Behavioural and Clinical Neuroscience Institute (BCNI), an initiative jointly funded by the MRC and the Wellcome Trust. MJWS was supported by an MRC Doctoral Training Grant and the James Baird Fund at the Medical School of the University of Cambridge. ALM was partly supported by a BCNI lectureship and the Ferreras-Willetts Fellowship from Downing College, Cambridge.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/npp.2015.24
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