Sara Muñoz-Vallés

Zinc tolerance and accumulation in the salt-marsh shrub Halimione portulacoides.

The halophytic shrub Halimione portulacoides is known to be capable of growth in soils containing extremely high concentrations of Zn. This study evaluated in detail the tolerance and accumulation potential of H. portulacoides under moderate and high external Zn levels. A greenhouse experiment was conducted in order to investigate the effects of a range of Zn concentrations (0-130 mmol L(-1)) on growth and photosynthetic performance by measuring relative growth rate, total leaf area, specific leaf area, gas exchange, chlorophyll fluorescence parameters and photosynthetic pigment concentrations. We also determined the total zinc, nitrogen, phosphorus, calcium, magnesium, sodium, potassium, iron and copper concentrations in the plant tissues. H. portulacoides demonstrated hypertolerance to Zn stress, since it survived with leaf concentrations of up to 2300 mg Zn kg(-1)dry mass, when treated with 130 mmol Zn L(-1). Zinc concentrations greater than 70 mmol L(-1) in the nutrient solution negatively affected plant growth, in all probability due to the recorded decline in net photosynthesis rate. Our results indicate that the Zn-induced decline in the photosynthetic function of H. portulacoides may be attributed to the adverse effect of the high concentration of the metal on photosynthetic electron transport. Growth parameters were virtually unaffected by leaf tissue concentrations as high as 1500 mg Zn kg(-1)dry mass, demonstrating the strong capability of H. portulacoides to protect itself against toxic Zn concentrations. The results of our study indicate that this salt-marsh shrub may represent a valuable tool in the restoration of Zn-polluted areas.

Tolerance and accumulation of copper in the salt-marsh shrub Halimione portulacoides.

The present study evaluated the tolerance and accumulation potential in the salt-marsh shrub Halimione portulacoides under moderate and high external Cu levels. A greenhouse experiment was conducted in order to investigate the effects of a range of external Cu concentrations (0 to 60 mmol l(-1)) on growth and photosynthetic performance by measuring gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments. We also determined total copper, nitrogen, phosphorus and sulfur concentrations in the plant tissues. H. portulacoides survived with external Cu concentrations of up to 35 mmol Cu l(-1), although the excess of metal resulted in a biomass reduction of 48%. The effects of Cu on growth were linked to a drastic reduction in net photosynthesis. However, H. portulacoides tolerated Cu levels of up to 15 mmol Cu l(-1) without suffering adverse physiological effects. Our results indicate that this species could play an important role in the restoration of Cu-contaminated soils.

Effects of soil physicochemical properties on plant performance of Glaucium flavum Crantz

Background and aimsGlaucium flavum is an endangered coastal herb capable of growth in a wide variety of ecosystems. We explore plant-soil relationships in this species by evaluating plant performance and soil physicochemical properties in the different types of ecosystems where it grows.MethodsTen natural populations from southern Spain were chosen for the study. In each experimental site, a number of variables related to the growth, reproduction and nutritional status of G. flavum were studied and an analysis of the soil physicochemical properties (texture, pH, electrical conductivity and total N, P, S and Ca concentration) was conducted. Data were statistically analyzed in order to characterize the habitat of G. flavum and to explore possible relationships between the studied variables.ResultsAt all experimental sites, the soil presented an alkaline pH and high concentrations of Ca. Despite the low levels of soil N, P and S, our data did not indicate nutrient deficiencies in leaf tissues. The percentage of reproductive plants and number of seeds per fruit correlated positively with leaf Ca concentrations.ConclusionsIncreasing Ca concentrations in plant tissues and elevated soil pH have a positive effect on plant performance of G. flavum.