Tree-ring growth of silver fir (Abies alba Mill.) in two stands under different silvicultural systems in central Italy

A preliminary analysis was made of growth trends in two silver fir forests in the Apennines in central Italy. The forests are closely located but were managed differently in the past. The aim was to verify the climatic variation over time, the influence of extreme events on radial growth and the role of silvicultural systems in defining growth response. The two forests have distinct structures due to differing past silvicultural management. The Camaldoli Forest, containing one-storeyed, evenaged, pure silver fir stands, was essentially managed in the past for wood production and featured high plantation density, low to moderate thinning, and clear cutting every 80–100 years. The La Verna Forest includes multi-layered, unevenaged stands that are mixed in with beech and other broadleaves. Increment cores were collected from aged dominant and healthy trees in the two forests. Climatic data were taken from the Camaldoli station and covers the period 1885–1994. All the analysed dendroecological parameters displayed similar patterns and indicated suitable site conditions for the silver fir. Silvicultural systems played an important role in defining growth pattern and rate. In the evenaged system there were higher growth rates and a greater number of pointer years, whereas there were lower growth rates and long, homogeneous development stages in the semi-natural conditions of La Verna. A rising growth trend recorded in the last three decades in both series could be explained by the consistent extension of the growing season due to a significant increase of mean spring and autumn temperatures. No correlation was found with precipitation while significant correlations were found between tree ring growth and February, April and August temperatures. Preliminary results indicated that the silvicultural system does not bias, but just enhances the ability of the species to record the effects of disturbing factors.     

Local seed dispersal in European silver fir (Abies alba Mill.): lessons learned from a seed trap experiment

Seed dispersal is an important factor influencing the genetic structure of forest tree populations. Knowledge about the seed shadow is important to assess the ability of tree species to colonize new and disturbed habitats or to respond to environmental change by migrating to more suitable habitats. In a seed trap experiment, we investigated local seed dispersal distances of silver fir seeds (Abies alba Mill.) by explicitly identifying mother trees. For this purpose, we matched microsatellite genotypes of maternal tissues of seeds with the genotypes of adult trees in the studied stand. Furthermore, we analysed the effect of morphological traits on dispersal distance, and we assessed the number of contributing mother trees and compared the seed density of the closed forest-stand with the adjacent blowdown. Based on 674 seeds collected in a grid of 37 seed traps, a significant decline in seed density was observed from within the forest to the forest blowdown area >40 m from the forest edge. A median dispersal distance of 31 m was determined for filled seeds based on direct assignment of seeds to their mother trees. This was higher than that determined in the previous studies using different methods. Dispersal distance was negatively correlated to seed-weight, but this was partially compensated for by the length of seed wings. A very large number of unassigned maternal genotypes (435) suggested that dispersal distance might have been underestimated. Lessons for future studies were: to perform a full genotypic inventory of adult trees in a defined perimeter, to increase the number of microsatellite markers and to study several sites over a period of several years.     

Geographic variability of monoterpenes from cortex of Abies concolor

Cortical oleoresin from 351 Abies concolor trees collected in 43 localities was analyzed for composition of its monoterpenoid fraction. The populations could be segregated into three geographic groups: (1) Northern and Central California (equivalent to var. Iowiana), producing camphene and 3-carene in trace to small amounts; (2) Southern California (the Cuyamaca race), producing camphene in trace to small and 3-carene in larger amounts; and (3) states to the east of California (equivalent to var. concolor) producing camphene and 3-carene in larger amounts. California populations from the southernmost Sierra Nevada and Northern Transversal Ranges were found to be chemically intermediate between var. Iowiana and var. concolor. Statistical analysis indicated the presence of additional second-order segregations in each of the four population groups, The results are explained on the basis of existing paleobotanical records.     

Monoterpene hydrocarbon contents of the resin from seeds of silver fir (Abies alba Mill.)

Summary Using gas-chromatographic methods, the variability of the contents of monoterpene hydrocarbons (-pinene, -pinene, ₃carene and limonene) in the resin of silver fir seeds (Abies alba Mill.) was studied. Resin cavities were characterized according to their position on the seed surface. It was estabilished that the terpene content of the resin of cavities localized on the abaxialadaxial surfaces of the seed differs significantly, creating a gradient of resin composition around the circumference of the seed. The differences between various resin cavities of single seeds were greater than the differences between different seeds of a single cone and between seeds of various cones on a single tree. An accurate definition of the resin cavity location on the seeds appears to be a fundamental condition for the collection of a sample representing the resin composition of individual trees. Resin biosynthesis in the course of organogenesis and the control of terpene contents in the resin of various locations on the seed and the cone are discussed.     

Growth stimulation in bean (Phaseolus vulgaris L.) by Trichoderma

Trichoderma species are commonly used as biological control agents against phytopathogenic fungi and some strains are able to produce metabolites that enhance plant growth. In the current study we evaluated the production of potential growth-promoting metabolites, rhizosphere competence and endophytism for 101 isolates of Trichoderma from Colombia, and assessed the relationship of these factors to the enhancement of early stages of growth on bean seedlings. Twenty percent of these Trichoderma strains were able to produce soluble forms of phosphate from phosphoric rock. Only 8% of the assessed strains showed consistent ability to produce siderophores to convert ferric iron to soluble forms by chelation. Sixty percent of isolates produced indole-3-acetic acid (IAA) or auxin analogues. The production of any of these metabolites was a characteristic of specific strains, as the ability to produce these metabolites varied greatly within species. Moreover, the production of these substances did not correlate with enhanced growth on bean seedlings, measured as the combined increase in length of roots and aerial parts in the V3 stage of growth. Seven Trichoderma isolates significantly improved the growth of bean seedlings. However, metabolite production varied widely in these seven strains, and some isolates did not produce any of the assessed growth-promoting metabolites. Results indicated that growth was enhanced in the presence of rhizosphere competent and endophytic strains of Trichoderma, and these characteristics were strain-specific and not characteristic for species.     

In vivo and in vitro effects of copper and cadmium on the plasma membrane H+-ATPase from cucumber (Cucumis sativus L.) and maize (Zea mays L.) roots

The plasmalemma vesicles isolated from cucumber and maize roots were used to study the effect of Cu²⁺ and Cd²⁺ on the hydrolytic and proton pumping activities of ATPase. In vivo application of metal ions to the plant growth solutions resulted in stimulation of the proton transport in maize. In cucumber roots the action of metals was not the same: cadmium stimulated the H⁺ transport through plasmalemma whereas Cu²⁺ almost completely inhibited it. Copper ions decreased the hydrolytic activity of H⁺-ATPase in cucumber, without any effect on this activity in membranes isolated from maize roots. The effect of cadmium on the hydrolytic activities was opposite: ATP-hydrolysis activity in plasmalemma was not altered in cucumber, whereas in maize its stimulation was observed. The amount of accumulated metals was not the main reason of different influence of metals on H⁺-ATPase activity in tested plants. In in vitro experiments Cu²⁺ inhibited H⁺ transport in the cucumber, to a higher degree than Cd²⁺ and both metals did not change this H⁺-ATPase activity of plasmalemma isolated from corn roots. Cu²⁺ added into the incubation medium reduced the hydrolytic activity of ATPase in the plasma membrane isolated from cucumber as well as from corn roots. Cd²⁺ diminished the hydrolytic activity of ATPase in cucumber, and no effect of Cd²⁺ in the plasmalemma isolated from corn roots was found. Our results indicated different in vitro and in vivo action of both metals on H⁺-ATPase and different response of this enzyme to Cu²⁺ and Cd²⁺ in maize and cucumber.     

Physiological performance of silver-fir (Abies alba Mill.) populations under contrasting climates near the south-western distribution limit of the species

Silver-fir (Abies alba Mill.) populations located at the south side of the main Pyrenean axis and Pre-Pyrenees constitute the south-western distribution limit of the species and, therefore, may be responding more noticeably to climate change than those in the centre of the range. The increasing aridity detected in the Pyrenees during the 20th century should affect more negatively the physiological performance of the southernmost silver-fir stand growing under more xeric conditions in comparison with stands growing within the main distribution area under mesic conditions. To evaluate the climatic influence on the performance of silver fir near its distribution limit, we studied several physiological and growth variables in shoots and needles from two silver fir populations located in nearby but climatically contrasting sites: Paco Ezpela (site E) and Gamueta (site G). Site E showed a stronger Mediterranean influence than site G, i.e. the former site was characterized by higher temperatures and leaf-to-air water vapour pressure difference and lower precipitation in summer than the latter site. Silver firs from site E showed lower values of primary and secondary growth, needle length, stomatal conductance, net photosynthesis and photosystem II (PSII) efficiency than individuals from site G. The reduction in net photosynthesis could be ascribed to a low CO₂ availability and to a lower PSII efficiency. We conclude that the physiological differences found between both sites were caused by the more xeric conditions of site E as compared with the more mesic environment in site G. The predicted increase of severe droughts in the southern Pyrenees might cause a decrease in photosynthesis and growth in those silver-fir stands located near the ecological limit of the species.     

Belowground Interactions in a Vine (Vitis vinifera L.)-tall Fescue (Festuca arundinacea Shreb.) Intercropping System: Water Relations and Growth

In the Mediterranean area, the introduction of cover crops in vineyards is hampered by the risk of severe competition for water. Belowground interactions are still not very clear in this perennial-herbaceous association. This work was aimed at characterizing the development of the root systems of associated crops and the soil water dynamics. It also investigated whether water competition could be the cause of vine vigour and yield reductions. Experiments were conducted in a 4-year-old association (vine – tall fescue) and in a weed controlled vineyard. Water transfers in the soil were estimated on the basis of the soil water potential and soil hydrodynamic properties. The vine root system was concentrated in the soil under the row, whereas the intercrop highly colonized a soil compartment under the inter-row to a depth of approximately 1 m. Despite this spatial complementarity in root distribution, intercropping reduced the amount of soil water available for the vine crop. The low soil water content reduced soil water conductivity thereby limiting water transfers, despite a significant gradient in the soil water potential. This conductivity did not differ significantly between treatments but the intercrop enhanced the infiltration of winter rainwater, probably by limiting surface runoff. There was temporal complementarity in this association since the period of intense water uptake by the intercrop occurred earlier than noted for the vine under bare soil conditions. Nevertheless, the competition for water was limited by better refilling of the soil water profile during winter in the intercropped treatment. The intercrop clearly interacted with the vine and decreased its vegetative vigor. Since predawn leaf water potential and stomatal conductance did not differ among treatments, mechanism(s) other than competition for water (e.g. nutrient competition, allelopathy) may be responsible.     

Caffeic acid inhibits in vitro rooting in mung bean [Vigna radiata (L.) Wilczek] hypocotyls by inducing oxidative stress

Caffeic acid (CA), which is ubiquitously present in plants, is a potent phytotoxin affecting plant growth and physiology. The aim of our study was to investigate whether CA-induced inhibition of adventitious root formation (ARF) in mung bean {Vigna radiata (L.) Wilczek [Phaseolus aureus Roxb.]} involves the induction of conventional stress responses. The effect of CA (0–1000 μM) on ARF in mung bean was determined by measuring the generation of reactive oxygen species (ROS) in terms of malondialdehyde and hydrogen peroxide (H₂O₂) content, root oxidizability and changes in levels of antioxidant enzymes. Our results show that CA significantly enhanced MDA content, indicating severe lipid peroxidation, and increased H₂O₂ accumulation and root oxidizability in the lower rooted hypocotylar region (LRHR) of mung bean, thereby inducing oxidative stress and cellular damage. In response to CA, there was a significant upregulation in the activities of scavenging enzymes, such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, catalase and glutathione reductase, in LRHRs of mung bean. Based on these results, we conclude that CA inhibits ARF in mung bean hypocotyls by inducing ROS-generated oxidative stress and upregulating the activities of antioxidant enzymes.     

Growth and longevity of Mytilus edulis (L.) from northeast Europe

The growth of mussels, Mytilus edulis (L.), was studied in most of the northeastern part of their distribution. The growth, longevity and maximal size of molluscs from 24 wild populations and one cultured population located in the White Sea and the southeast part of the Barents Sea were compared. The 25 studied populations were combined in six clusters. The maximal longevity and the size of the mussels varied between 7 and 18 years and 25.5 and 77.7 mm, respectively. The geographical location of the population within the studied region did not affect either maximal longevity or maximal size, or the growth rate of mussels. However, these parameters were influenced by local habitat conditions, primarily connected with the position within intertidal and subtidal zones. Animals inhabiting the intertidal zone were characterized by relatively low growth performance, a short life span and a small size. The longest life span was typical for deep subtidal mussels, whereas the highest growth rate was recorded in the cultured population and in the upper subtidal habitats. Growth patterns of Mytilus edulis in the subarctic White and the Arctic southeast Barents seas are similar to those reported from other parts of the area of distribution. Therefore, growth was mostly determined by local environmental factors, including those related to vertical zonation, rather than by latitude/longitude and related temperature effects.     

A procedure for mini-preparations of genomic DNA from needles of silver fir (Abies alba mill.)

We have adapted a procedure for the isolation of genomic DNA from needles of silver fir (Abies alba) to meet the requirements for large-scale analysis of the population genetics of forest trees. Our modifications permit the entire procedure to be carried out in Eppendorf tubes, which greatly minimizes time, plant material, and the amounts of chemicals. DNA is recovered with a mean efficiency of 80 μg/g needles, is suitable for restriction by the common endonucleases, and serves as a substrate for PCR.     

Plant regeneration from callus cultures derived from mature zygotic embryos in white pine (Pinus strobus L.)

Plant regeneration via adventitious shoot organogenesis from callus cultures initiated from mature embryos in white pine (Pinus strobus L.) was achieved in this study. Callus cultures were induced from mature embryos cultured on PS medium supplemented with 2,4-dichlorophenoxyacetic acid, -naphthaleneacetic acid, or indole-3-acetic acid. Adventitious shoot regeneration from callus cultures was induced on medium containing 2 M indole-3-butyric acid (IBA) and 3–12 M N₆-benzylaminopurine, thidiazuron (TDZ), or 6-(,-dimethylallylamino) purine. Sucrose was the most suitable sugar for adventitious shoot organogenesis in white pine. Shoot organogenesis was improved by treatment at 4°C for 6 weeks. The frequency of adventitious shoot formation increased when 0.1 mM putrescine was added to basal medium supplemented with 6 M TDZ and 2 M IBA. Putrescine improved adventitious shoot organogenesis by decreasing lipid peroxidation. These findings provide useful information on adventitious shoot organogenesis and may be valuable to genetic transformation in white pine.     

Hydrolysates from Atlantic cod (Gadus morhua L.) viscera as components of microbial growth media

Three hydrolysates made from cod viscera by different enzymatic hydrolysis procedures were tested as a combined source for nitrogen, amino acids and vitamins in microbial growth media. Using a panel of five different microbes: Escherichia coli, Bacillus subtilis, Lactobacillus sakei, Saccharomyces cerevisiae and Aspergillus niger, the performance of these viscera hydrolysates was compared to the performance of common commercial peptones in an automated growth analyzer (Bioscreen C). The results show that the fish hydrolysates in general are promising alternatives to currently available commercial nitrogen sources of other origins. In the case of the food-grade and nutritionally fastidious L. sakei, two of the fish hydrolysates were clearly superior to all tested commercial peptones. For several microbes, the choice of the proteolytic enzymes used to produce the fish hydrolysate had considerable impact on performance of the resulting hydrolysate, both in terms of maximum growth rate and biomass production. In terms of hydrolysate performance, the generally best enzyme for production of a fish peptone from cod viscera was found to be Alcalase.     

Coexistence of Abies alba (Mill.) - Fagus sylvatica (L.) and climate change impact in the Iberian Peninsula: A climatic-niche perspective approach

Abies alba Mill. (European silver fir) and Fagus sylvatica L. (beech) are Eurosiberian species dispersed over the Iberian Peninsula. Climate change predictions indicate a rise in temperature and a decrease in precipitation in this region, threatening the future existence of these species. In the present study we analyzed the future topo-climatic suitability of Abies alba and Fagus sylvatica and the mixed forests of these two species, using the General Linear Models technique and data from the third National Forest Inventory (Ministerio de Agricultura PyA, 2007). We considered two modeling approaches based on niche theory: modeling community (Abieti-Fagetum) and overlapping individual species models. General trends showed an overall decrease in both species’ topo-climatic suitability and indicated that the Pyrenees will play a crucial role as a climatic refuge. The modeling approaches markedly differed, however, in their current and future spatial agreement. Despite good accuracy results, community modeling through co-occurrence does not encompass the environmental space of individual species prejudicing future assessments in new environmental situations, suggesting a need for future studies in community modeling.     

Antileishmanial activity of a guaianolide from Tanacetum parthenium (L.) Schultz Bip

Leishmaniasis is one of the major infectious diseases affecting the poorest regions of the world. The present study evaluated the antileishmanial activity of a guaianolide purified from the hydroalcoholic extract of aerial parts of Tanacetum parthenium (L.) Schultz Bip. The isolated compound showed activity against the promastigote form of Leishmania amazonensis, with 50% inhibition (IC₅₀) of cell growth at a concentration of 2.6 μg/ml. For the intracellular amastigote form, this guaianolide reduced by 10% the survival index of parasites in macrophages when it was used at 20.0 μg/ml. The selective index (SI) ratio (CC₅₀ for J774G8 cells/IC₅₀ for protozoans) was 385, showing that it is more selective against the parasite than mammalian cells. Morphological alterations of protozoans treated with IC₅₀ included changes in size, shape, and structure (more than one nucleus and flagellum) under both light and scanning electron microscopies.     

Spatial and altitudinal bioclimatic zones of the Italian peninsula identified from a beech (Fagus sylvatica L.) tree-ring network

A network of 24 beech (Fagus sylvatica L.) tree-ring chronologies has been developed for the Italian peninsula. Principal component and cluster analyses were used to identify geographical and altitudinal patterns of tree growth. Correlations and response functions were then applied to the main modes of tree-ring variability to uncover climatic signals. In a landscape occupied by humans for millennia, this approach provided a detailed quantitative ecological characterization of forest types. Altitude was significantly correlated with dendrochronological parameters. The Alps and northern Apennines could be distinguished from the central-southern Apennines. In central Italy, we recognized three different vegetation belts occupied by beech forests, from low- to high-elevation sites. Summer drought impacted beech growth with different intensity at different elevations, depending on the onset and duration of the growing season. Moreover, low-elevation beech forests showed a distinct late spring climate signal, which was opposite to that of high-elevation sites. The coherent geographical and ecological patterns of tree-ring variability suggest that dendrochronological networks help define bioclimatic zones and forest types.     

Growth reactions of Pinus sylvestris L. and Quercus pubescens Willd. to drought years at a xeric site in Valais, Switzerland

In Valais, an inner-Alpine dry valley in Switzerland, low-elevation Scots pine (Pinus sylvestris L.) forests are changing. While pine shows high mortality rates, deciduous species, in particular pubescent oak (Quercus pubescens Willd.), are becoming more abundant. We hypothesise that increasing drought and the species-specific drought tolerance are key factors in these processes. In this study, the growth reaction to drought years of pine and oak growing at a xeric site in Valais was analysed using dendrochronological and wood anatomical methods. Congruent with theoretical expectations, the tree-ring widths of both species, the mean lumen area of earlywood vessels in oak and the number of tracheids in a radial row in pine decreased in response to dry conditions. However, both species also showed reactions deviating from those known from mesic sites: In oak, the mean lumen area of latewood vessels increased in drought years. In pine, in the driest year of the period (1976), the mean radial diameter increased in latewood and decreased only slightly in earlywood. These results emphasises that the process of wood formation and cell functionality at xeric sites is not completely understood yet. Both species seem to have difficulties to adapt the size of their water-conducting cells to strongly reduced water availability in drought years. Additionally, the cell number is strongly reduced. Thus it remains unclear if both species can maintain sufficient water transport under increasingly dry conditions.