Different drought-adaptive capacity of a native Patagonian tree species (Nothofagus pumilio) resulting from local adaptation

European Journal of Forest Research - The resistance of different genotypes to abiotic stress may be due to genetic effects and/or to phenotypic plasticity allowing them to acclimate to variable...     

Acute Effect of Ammonia and Nitrite on Respiration of Penaeus setiferus Postlarvae under Different Oxygen Levels

The white shrimp Penaeus setiferus is a potential species for culture in the Gulf of Mexico. It has been demonstrated that postlarval P. setiferus is a species sensitive to ammonia and nitrite. In this study, the effect of ammonia and nitrite on the oxygen consumption of Penaeus setiferus postlarvae subjected to different dissolved oxygen concentrations was investigated. Un-ionized ammonia tended to reduce the oxygen consumption of P. setiferus postlarvae. The addition of 0.4 mg/L un-ionized ammonia-N modified the response of the postlarvae to lower dissolved oxygen levels. Exposure to 0.7 mg/L un-ionized ammonia-N caused severe effects on the respiratory rate and it was lethal at low dissolved oxygen concentrations. Nitrite exposure decreased the respiratory rate of post-larvae in high dissolved oxygen concentrations, whereas postlarvae exposed to nitrite under hypoxic conditions showed higher oxygen consumption than unexposed animals. The decreases of the oxygen consumption induced by the interactive effect of ammonia or nitrite and low dissolved oxygen concentration indicate a harmful condition. The results indicate that P. setiferus postlarvae is a sensitive organism to the combined effect of un-ionized ammonia or nitrite and low dissolved oxygen concentrations.     

Acute Toxicity of Ammonia and Nitrite to White Shrimp Penaeus setiferus Postlarvae

Penaeus setiferus postlarvae were exposed to acute levels of ammonia, nitrite, and to a mixture of both by a short-term static method, The 24h, 48-h and 72-h LC50 values for un-ionized ammonia were 1.49, 1.21 and 1.12 mg/L NH₃-N (un-ionized ammonia as nitrogen), and 11.55, 9.38 and 8.69 mg/L ammonia-N (un-ionized plus ionized ammonia as nitrogen). The 24-h, 48-h and 72-h LC50 values for nitrite were 268.06, 248.84 and 167.33 mg/L nitrite-N (nitrite as nitrogen). Nitrite was much less toxic than ammonia. The joint effect of ammonia and nitrite on the postlarvae was synergistic at 48-h exposure and antagonistic after 72 h. Postlarvae of P. setiferus may be considered as organisms sensitive to ammonia and nitrite.     

Variation of wood density and hydraulic properties of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) clones related to a heat and drought wave in France

Drought response of three Douglas-fir clones (slow, intermediate and fast growing) inhabiting two different climatic regimes in France was examined. We used the hydraulic conductivity and the percent loss of conductivity due to embolism from stems and branches as well as wood microdensity measurements to determine the role of genetics in the control of embolism in this species. Conductivity and tree-ring’s microdensity variables (ring width: RW, mean ring density: MRD, minimum ring density: MID and maximum ring density: MAD) were compared in growth rings in all three clones during a typical year (2002) vs. an extremely dry year (2003). A new method was developed in order to assess axial hydraulic specific conductivity (K_s) within tree rings. The results show that branches are more resistant to embolism than stems, and that there are significant differences in embolism resistance among the clones between the two sites. K_s varied between years, sites and clones but the site exerted the most significant effect. Lartimache (more humid site during 2003) trees showed substantially higher K_s than those inhabiting Chassenoix (strongly affected by the 2003 heat and drought wave site). Wood analysis showed a significant year effect for all ring variables and a significant clone effect for all ring variables except for MAD, while the site effect was significant for MRD and MAD. The existence of a genetic control for the study traits indicates that Douglas-fir populations introduced in France may have a selection potential to face extreme climate events like the 2003 heat and drought wave.     

Interaction between jasmonic and gibberellic acids on in vitro tuberization of potato plantlets

Summary A reverse of the delaying effect of gibberellic acid (GA₃) was observed in in vitro tuberization of potato plantlets when the medium contained 0.8×10⁻⁵ M jasmonic acid (JA). The promoting effect of JA seemed to be correlated with the initial absence of growing roots, probably through direct activity of JA in microtuber-producing buds in the stoloniferous shoots. This is based on the fact that JA did not inhibit root growth a posteriori. Endogenous gibberellins (GAs) synthesized by roots did not interfere with the previous activity of JA in tuberization. The absence of a JA promoting-effect on tuberization of previously-rooted plantlets could be related to the capacity of potato roots to synthesize endogenous GAs which might antagonize the JA effect on buds of stoloniferous shoots.     

Ring density record of phenotypic plasticity and adaptation to drought in Douglas-fir

Microdensity profiles of Douglas-fir's clones and weather data were used to study phenotypic plasticity (dendroplasticity). Within-ring microdensity was interpreted as the variation of tree response to drought constraints during selected growing seasons. An original norm of reaction was obtained by pairing evident points of abrupt changes in tree-ring microdensity profiles and in weather indices. The coefficients of the non-linear models adjusted to the reaction norms were analysed as dendroplasticity variables. Dendroplasticity variables were significantly different between geographical locations, years and clones. Heritability of the dendroplasticity variables ranged from low to high and was similar to heritability values of microdensity variables such as mean ring density (MRD). Coefficients of genetic variation of dendroplasticity variables were intermediate between those of wood density and growth variables. Dendroplasticity variables were phenotypically and genetically related to ring microdensity variables, more strongly to latewood variables. Dendroplasticity provides retrospective, synthetic and easy-to-interpret information about tree response to the variation of the balance between water availability and water demand during the growing season. The proposed model of dendroplasticity is described by a number of parameters that are linked to a biological meaning. Our results suggest that there is a potential for adaptation to drought in Douglas-fir, with two mechanisms involved: at individual level, short-term plastic response during the growing season and, at population level, long-term, between-generation, evolution process.     

Leaf and litter nitrogen and phosphorus in three forests with low P supply

We compared the N and P contents of the main labile components of nutrient cycles in three different forest ecosystems [a tropical evergreen forest (TEF); a tropical dry forest (TDF); and a Mediterranean temperate forest (MTF)] with low P supply. A mass-balance approach was used to estimate mean residence times for organic matter, N and P in the forest floor, and to examine the flexibility of N and P intra-system cycling in the three forest ecosystems. For this purpose, we combined published values of N and P in foliage, litterfall, forest floor litter and mineral soils in these three forest ecosystems. The results of our analysis were consistent with the widely held belief that the N content of leaves (both green and senescent) and litter increases with increasing temperatures. In contrast, the data did not support the hypothesis that leaf P content decreases with increasing temperatures and precipitation: leaf and litterfall P contents were higher in both tropical forests than they were in the temperate forest. The TEF had the highest P content of the three forests studied. The mass-balance analysis indicated that although P mineralization in the TDF can run ahead of litter decomposition stoichiometry when P is in short supply, flexibility is much reduced or absent in the TEF and the MTF. Our analysis provides additional evidence of the importance of climatic factors in forest ecosystem processes and highlights the role of flexibility in ecosystem nutrient cycling, especially for P in ecosystems with a limited P supply.     

Assessment of pesticide residues in honey samples from portugal and Spain

Fifty samples of honey collected from local markets of Portugal and Spain during year 2002 were analyzed for 42 organochlorine, carbamate, and organophosphorus pesticide residues. An analytical procedure based on solid-phase extraction with octadecyl sorbent followed by gas chromatography-mass spectrometry (GC-MS), for organochlorines, and by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), for organophosphorus and carbamates, has been developed. Recoveries of spiked samples ranged from 73 to 98%, except for dimethoate (40%), with relative standard deviations from 3 to16% in terms of repeatability, and from 6 to 19% in terms of reproducibility. Limits of quantification were from 0.003 to 0.1 mg kg(-)(1). Most of the pesticides found in honey were organochlorines. Among them, gamma-HCH was the most frequently detected in 50% of the samples, followed by HCB in 32% of the samples and the other isomers of HCH (alpha-HCH and beta-HCH) in 28 and 26% of the samples, respectively. Residues of DDT and their metabolites were detected in 20% of the samples. Of the studied carbamates, both methiocarb and carbofuran were detected in 10% of the samples, pirimicarb in 4% and carbaryl in 2%. The only organophosphorus pesticides found were heptenophos in 16%, methidathion in 4%, and parathion methyl in 2% of honey samples. Results indicate that Portuguese honeys were more contaminated than Spanish ones. However, honey consumers of both countries should not be concerned about the amounts of pesticide residues found in honeys available on the market.     

Development of a competitive ELISA for the evaluation of sunflower pollen in honey samples

We report the development of a rapid, specific, and sensitive enzyme-linked immunoassay (ELISA) for the evaluation of sunflower pollen in honey as a method alternative to melissopalynology, which is considered the standard technique for the evaluation of floral origin of honey. Two 33-36 kDa proteins, identified as characteristic of sunflower pollen, were isolated and used as coating antigens in the competitive ELISA. We verified its analytical performance by evaluating reproducibility, specificity, and exactitude in relation to melissopalynology. The competitive ELISA developed during this work is able to quantify sunflower pollen in honey, with a detection limit of 10%, showing linear response between 10 and 90%. The method afforded low cross reactivity with honey from other floral origin, thus evidencing an adequate selectivity. We also observed a significant correlation (r = 0.975; p < 0.001) when the proposed ELISA was referenced to melissopalynology. Hence, we conclude that the competitive ELISA constitutes a valuable and feasible alternative for authentication of sunflower honey. This work opens the possibility to develop similar assays for other pollen types.