Long-term trends in dominant-height growth of black pine using dynamic models

Black pine (Pinus nigra Arn.) is a pan-Mediterranean species of high ecological importance and one of the most important timber species in the area. We compare several site dependent height–age models for the species in three regions along its natural distribution area in Spain. The best model was a generalized algebraic difference approach (GADA) polymorphic model with variable asymptotes (Cieszewski, C.J., Bailey, R.L., 2000. Generalized algebraic difference approach: theory based derivation of dynamic site equations with polymorphism and variable asymptotes. For. Sci. 46, 116–126). There was no significant increase in error when a reduced model common to the three regions was tested instead of a full model with region-specific parameters. To study possible biases of the proposed model along the trees’ lifespan we carried out a LOWESS analysis of residuals in time. We detected deviations in the model residuals, and a patent growth reduction in the 1960s and 1970s, which might be related to climate and/or changing stand characteristics. Departures from estimated mean past growth should be monitored in the future to adapt models to a changing environment.     

Yield and quality evaluations on a pair of processing tomato lines nearly isogenic for the Tm2a gene for resistance to the tobacco mosaic virus

A pair of processing tomato (Lycopersicon esculentum Mill.) lines, nearly isogenic for the Tm-2^a gene for resistance to tobacco mosaic virus, were grown in replicated trials under commercial production conditions in five locations worldwide. The lines were evaluated for 17 processing traits including fruit yield, size, soluble solids concentration, color, firmness, and viscosity. Eight of those traits differed significantly among the nearly-isogenic lines (NILs). Most notably, the NIL heterozygous for Tm-2^a yielded, on average, 16% more than the NIL homozygous for the susceptible allele and 33% more than the NIL homozygous for Tm-2^a. Viscosity was lower in the heterozygous NIL and the homozygous and heterozygous resistant NILs had softer fruit with larger stem scars compared to the homozygous susceptible NIL. These results indicate the presence of the Tm-2^a locus affects many traits of importance for processing tomatoes and may be used, in the heterozygous state, to significantly increase yield. Whether the observed effects are due to the Tm-2^a gene itself or genes associated via linkage drag could not be determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Potential Biomedical Applications of Collagen Filaments derived from the Marine Demosponges Ircinia oros (Schmidt, 1864) and Sarcotragus foetidus (Schmidt, 1862)

Collagen filaments derived from the two marine demosponges Ircinia oros and Sarcotragus foetidus were for the first time isolated, biochemically characterised and tested for their potential use in regenerative medicine. SDS-PAGE of isolated filaments revealed a main collagen subunit band of 130 kDa in both of the samples under study. DSC analysis on 2D membranes produced with collagenous sponge filaments showed higher thermal stability than commercial mammalian-derived collagen membranes. Dynamic mechanical and thermal analysis attested that the membranes obtained from filaments of S. foetidus were more resistant and stable at the rising temperature, compared to the ones derived from filaments of I. oros. Moreover, the former has higher stability in saline and in collagenase solutions and evident antioxidant activity. Conversely, their water binding capacity results were lower than that of membranes obtained from I. oros. Adhesion and proliferation tests using L929 fibroblasts and HaCaT keratinocytes resulted in a remarkable biocompatibility of both developed membrane models, and gene expression analysis showed an evident up-regulation of ECM-related genes. Finally, membranes from I. oros significantly increased type I collagen gene expression and its release in the culture medium. The findings here reported strongly suggest the biotechnological potential of these collagenous structures of poriferan origin as scaffolds for wound healing.     

Effects of on‐demand feeding on sea urchin larvae (Paracentrotus lividus; Lamarck, 1816), development,survival and microalgae utilization

This study compared the growth of sea urchin Paracentrotus lividus larvae cultured using two different rearing methods: a variable method based on a variable amount of feed (microalgae) and seawater exchange (30% or 50%) established according to the phytoplankton concentration in the larval cultures and a fixed method characterized by a fixed amount of feed and seawater exchange. Three microalgae diets, Isochrysis sp. (Tahitian strain, T‐Iso), Chaetoceros gracilis and a 50:50 mixed diet, were tested with both rearing methods. Larval development and survival were assessed at the 6‐arm pluteus stage (P6), competence (Cp) and metamorphosis (Mt). Data showed that the variable method reduced the requirements for phytoplankton and seawater exchange. Indeed, through the optimization of feed rations, it was possible to reduce the production of debris and settled phytoplankton, minimizing the need for water exchanges. Higher larval survival resulted at Cp and Mt stages for those reared with the variable method as opposed to the fixed one. Survival and development were also influenced by the tested dietary treatments: at Mt stage, the mixed diet resulted in a higher larval survival (63.3 ± 8.9%) than T‐Iso (19.7 ± 12.1%) and C. gracilis (23.4 ± 15.1%) (P < 0.05). These results suggest that the use of the variable method improves the larval survival and development and also it reduces resource consumption (phytoplankton, seawater use and work effort), which in turn could potentially improve the hatchery production of P. lividus.     

Land use change and soil carbon pools: evidence from a long-term silvopastoral experiment

Multi-functional silvopastoral systems provide a wide range of services to human society including the regulation of nutrients and water in soils and the sequestration of atmospheric carbon dioxide (CO₂). Although silvopastoral systems significantly contribute to enhance aboveground carbon (C) sequestration (e.g. C accumulation in woody plant biomass), their long-term effects on soil C pools are less clear. In this study we performed soil physical fractionation analyses to quantify the C pool of different aggregate fractions across three land use types including (1) silvopastoral system with ash trees (Fraxinus excelsior L.), (2) planted woodland with ash trees, and (3) permanent grassland, which were established in 1989 at Loughgall, Northern Ireland, UK. Our results show that 26 years after the conversion of permanent grassland to either silvopastoral or woodland systems, soil C (and N) stocks (0–20 cm depth) did not significantly change between the three land use types. We found, however, that permanent grassland soils were associated with significantly higher C pools (g C kg^?1 soil; P < 0.03) of the large macro-aggregate fraction (> 2 mm) whereas soil C pools of the micro-aggregate (53–250 μm) and silt and clay (< 53 μm) fractions were significantly higher in the silvopastoral and woodland systems (P < 0.05). A key finding of this study is that while tree planting on permanent grassland may not contribute to greater soil C stocks it may, in the long-term, increase the C pool of more stable (recalcitrant) soil micro-aggregate and silt and clay fractions, which could be more resilient to environmental change.     

Correlation between lipid peroxidation and phenolics content in leaves and roots of sugar beet infected with Rhizoctonia solani

The correlation between intensity of lipid peroxidation and changes in antioxidant capacity of sugar beet plants (cv. ‘Drena’) infected with Rhizoctonia solani Kühn isolate (AG 2-2 IIIB group) was studied. Successful inoculation was confirmed by the presence of infection cushions in a cross section of leaf petioles. On the 7^th day of the experiment, phenylalanine ammonia-lyase (PAL; EC. 4.3.1.5) activity was in negative correlation with intensified lipid peroxidation process in leaves of sugar beet plants (r= –0 .99). Also, in leaves and roots of inoculated sugar beet plants, total flavonoids content (35% and 20%, respectively) and 1,1-diphenyl-2-picrylhydrazyl (DPPH)-scavenging activity (80% and 55%, respectively) were significantly reduced. Necrotic processes resulting from R. solani infection of sugar beet plants was followed by induction of plant phenolics metabolism; however, antioxidant capacity of these plants was reduced.     

Hybridization of two diploid Vaccinium section Cyanococcus species with diploid Vaccinium arboreum in section Batodendron

Several characteristics from sparkleberry (V. arboreum) would be useful if transferred to highbush blueberry cultivars, but to date all direct crosses have failed. The purpose of this research was to see whether crosses of diploid V. darrowii and diploid V. fuscatum (both section Cyanococcus) with diploid V. arboreum (section Batodendron) could be made and to assess the possibility of transferring traits from V. arboreum into cultivated blueberries of section Cyanococcus. Many crosses were successful and easy to make. Crosses were more productive when V. arboreum was the pollen parent, but some hybrids were also obtained with V. arboreum as seed parent. Pollen stainability of F₁ (V. darrowii × V. arboreum) hybrids was low, ranging from 0.9 to 23.7%. Numerous meiotic abnormalities were found in the F₁ hybrids. These led to a high percentage of incomplete and unstained tetrads and probably to the production of unreduced gametes.     

Evidence for niche differentiation of nitrifying communities in grassland soils after 44 years of different field fertilization scenarios

Long-term nitrogen(N)fertilization imposes strong selection on nitrifying communities in agricultural soil,but how a progressively changing niche affects potentially active nitrifiers in the field remains poorly understood.Using a 44-year grassland fertilization experiment,we investigated community shifts of active nitrifiers by DNA-based stable isotope probing(SIP)of field soils that received no fertilization(CK),high levels of organic cattle manure(HC),and chemical N fertilization(CF).Incubation of DNA-SIP microcosms showed significant nitrification activities in CF and HC soils,whereas no activity occurred in CK soils.The 44 years of inorganic N fertilization selected only 13C-ammonia-oxidizing bacteria(AOB),whereas cattle slurry applications created a niche in which both ammonia-oxidizing archaea(AOA)and AOB could be actively13C-labeled.Phylogenetic analysis indicated that Nitrosospira sp.62-like AOB dominated inorganically fertilized CF soils,while Nitrosospira sp.41-like AOB were abundant in organically fertilized HC soils.The 13C-AOA in HC soils were affiliated with the 29i4 lineage.The 13C-nitrite-oxidizing bacteria(NOB)were dominated by both Nitrospira-and Nitrobacter-like communities in CF soils,and the latter was overwhelmingly abundant in HC soils.The 13C-labeled nitrifying communities in SIP microcosms of CF and HC soils were largely similar to those predominant under field conditions.These results provide direct evidence for a strong selection of distinctly active nitrifiers after 44 years of different fertilization regimes in the field.Our findings imply that niche differentiation of nitrifying communities could be assessed as a net result of microbial adaption over 44 years to inorganic and organic N fertilization in the field,where distinct nitrifiers have been shaped by intensified anthropogenic N input.     

Phyto-dehydration of confined sludge: a sustainable approach for the management of polluted ponds

Purpose

Leaf transpiration drives many of the processes involved in phyto-technologies, and it can represent a useful mechanism to remove water from different kind of storage basins presenting inorganic, organic or microbiological contamination (phyto-dehydration), with the aim to reduce the risk of environmental contamination. In this framework, a mesocosm-scale trial was carried out to test the capacity of different helophyte species to reduce the excess of water in an artificial pond filled with oversaturated sludge.

Materials and methods

The sludge derives from the digestion of pig slurries, presents high levels of zinc and copper and for most of the year is covered by a water layer of about 20 cm due to rainfalls. This layout (water layer over the sludge) was reproduced inside the mesocosms, where four helophyte species (Phragmites australis and a mix of Carex acutiformis, Iris pseudacorus and Juncus effusus) were planted on floating frames. Plant growth and functionality were monitored for one year, along with their water consumption capacity; the vegetation impact on sludge chemistry, sludge microbial community and sludge greenhouse gases emission/uptake were also evaluated. The sensitivity of the phyto-dehydration system to the reduction of water level occurring during summer in the pond was investigated reducing the water input to the mesocosms.

Results and discussion

P. australis and C. acutiformis successfully established in the mesocosms, while a significant mortality was recorded for I. psudacorus and J. effusus. Once established, plants were able to grow in the mesocosms, and no metal toxicity effect was observed on photosynthesis rates that were comparable with values reported for natural stands of the species. Plants significantly increased (from 24 to 63%, depending on the species) the amount of water lost by the mesocosms and counteracted the reduction of sludge organic carbon that could lead to a mobilization of the heavy metals bound to organic matter: furthermore, plants decreased the rates of mesocosm greenhouse gas emission and reduced the sludge pathogen (Enterobacteriaceae) occurrence. Water limitations reversibly reduced the water consumption and CO₂ uptake capacity of the mesocosms.

Conclusions

The results of this study demonstrated that the water balance of a sludge/water system can be effectively modified through the phyto-dehydration approach, increasing significantly the amount of water lost. Although the low tolerance of two species to the sludge/water environment after plantation needs to be further investigated, this phyto-technology can represent a promising approach to manage the excess of water in polluted ponds.

     

RAPD variation in a germplasm collection of Myracrodruon urundeuva (Anacardiaceae), an endangered tropical tree: Recommendations for conservation

RAPD markers were used to investigate the distribution of genetic variability in a germplasm collection of the dioecious tropical tree Aroeira (Myracrodruon urundeuva) composed of open pollinated maternal half-sib families collected from trees at least 300 meters apart and grouped in nine collection areas throughout its geographical range in Brazil. Open pollinated families from nearby trees from two natural populations were also included in the study. A Principal Coordinate Analysis (PCO) based on genetic similarities estimated with 83 RAPD markers showed no defined clustering among individuals from the same collection areas. However, a matrix correlation test showed low, but significant correlation between genetic and geographic distances (r = 0.17; p < 0.02). An AMOVA showed that 92% of the genetic variation is found within collection areas. Significant variation was found both between regions and between areas within regions although only 3.54 and 4.44% of the variation was found at these levels respectively. An AMOVA on the individuals from the two natural populations resulted in a pattern of distribution congruent to the one found for the collection areas, with 97% of variability within populations. An analysis of 10 open-pollinated half-sib families revealed that between 75% and 89% of the variability is contained within families, suggesting that seeds from one tree represent a significant proportion of the variability found in the population. These results indicate that, either for the establishment of in situ genetic reserves or for ex situ conservation, efforts should be directed to the conservation of several individual trees or collection of open pollinated seed families in a few distant sites. In addition, if resources are available to enlarge the genetic base of the existing collection, expeditions should prioritize collection sites located in areas at significant distances to those already sampled.