Foraminifer communities and environmental change in marginal marine sequences (Pliocene,Tuscany, Italy)

Fossil abundance data on foraminifer communities were collected in marginal marine sediments of the Pliocene Valdelsa succession, in Tuscany, Italy. This succession is organized in a hierarchy of elementary and composite depositional sequences. Multivariate techniques allowed to analyse the dataset and reconstruct gradients in species distributions. Species‐level data available on modern environmental distributions were used to reconstruct Pliocene environmental gradients and to infer absolute palaeodepths and palaeosalinities. Estimates were then compared with the sequence‐stratigraphic interpretation to check for consistency. The high‐resolution stratigraphic framework allowed us to test the stability of foraminifer communities against ecological variations related to high‐frequency glacio‐eustatic cycles. The results confirm that fossil distributions of foraminifer species can be used as a fine tool to detect environmental change and that multivariate techniques allow their interpretation in terms of absolute variations of controlling parameters. Salinity is the main contributor to the sum of depth‐related factors that regulate foraminifer distributions in coastal facies. In the same setting, nutrient levels and the presence of a sea grass cover are responsible for secondary changes in shallow‐water distributions. Below the wave base, however, depth‐related parameters other than salinity explain the largest variations. This study indicates that foraminifer communities are random associations of species that respond individualistically to environmental change.     

Crocus imperati and Crocus suaveolens (Iridaceae), two controversial endemic crocuses from Central and Southern Italy – morphometrics,lectotypification and chorology

Crocus imperati Ten. and Crocus suaveolens Bertol. are the most controversial endemic crocuses in Italy; they have been interpreted by various authors as different species or infraspecific entities and their chorologies are afflicted by numerous misidentifications. This work, by means of an extensive in vivo study across the whole ranges of the two taxa, and using biometrical investigations, aims at clarifying their status. The names C. imperati and C. suaveolens are typified, several taxonomical complications are discussed and an accurate chorology is outlined. The results show that a single qualitative character is constant (the presence or absence of a bracteole) and two other characters allow discrimination in most cases; their combined use, therefore, ensures certain identification of any single individual. No hybrid individual or intermediate populations were detected and the distributional ranges of the two species were confirmed to be contiguous but not overlapping. As a consequence, treatment of the two taxa at specific level appears to be the most appropriate. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 194–214.     

TRAINING, VALIDATION AND MAINTENANCE OF A PANEL TO EVALUATE THE TEXTURE OF DRY BEANS (PHASEOLUS VULGARIS L.)

The inclusion of dry beans in diets has clear health benefits. However, consumers in developed countries mainly choose beans for their sensory qualities, especially for their texture. This article describes the constitution, training and validation of a panel of judges to evaluate the texture of dry beans. The judges were trained in the perception of different textures, analyzed a wide range of beans and selected seed-coat roughness, seed-coat perceptibility and creaminess/mealiness of the cotyledon as the main attributes to be scored. After training, the panel was capable of discriminating between different varieties of beans and even between beans of the same variety grown at different locations. The analysis of the behavior of the panel in a standard tasting session 2 years after its formation showed that periodic inclusion of samples from the extremes of the scales for the attributes during tasting sessions was sufficient to keep the panel trained.

PRACTICAL APPLICATIONS

This article could serve as a guide for the training of sensory panels to evaluate the texture of dry beans. It describes the selection of the attributes on which the analysis is based, references for the extreme values of the attributes and how to train the panel. It also provides a practical example of the analysis of the behavior of the panel some time after training.     

Simple three‐pool model accurately describes patterns of long‐term litter decomposition in diverse climates

As atmospheric CO₂ increases, ecosystem carbon sequestration will largely depend on how global changes in climate will alter the balance between net primary production and decomposition. The response of primary production to climatic change has been examined using well‐validated mechanistic models, but the same is not true for decomposition, a primary source of atmospheric CO₂. We used the Long‐term Intersite Decomposition Experiment Team (LIDET) dataset and model‐selection techniques to choose and parameterize a model that describes global patterns of litter decomposition. Mass loss was best represented by a three‐pool negative exponential model, with a rapidly decomposing labile pool, an intermediate pool representing cellulose, and a recalcitrant pool. The initial litter lignin/nitrogen ratio defined the size of labile and intermediate pools. Lignin content determined the size of the recalcitrant pool. The decomposition rate of all pools was modified by climate, but the intermediate pool's decomposition rate was also controlled by relative amounts of litter cellulose and lignin (indicative of lignin‐encrusted cellulose). The effect of climate on decomposition was best represented by a composite variable that multiplied a water‐stress function by the Lloyd and Taylor variable Q₁₀ temperature function. Although our model explained nearly 70% of the variation in LIDET data, we observed systematic deviations from model predictions. Below‐ and aboveground material decomposed at notably different rates, depending on the decomposition stage. Decomposition in certain ecosystem‐specific environmental conditions was not well represented by our model; this included roots in very wet and cold soils, and aboveground litter in N‐rich and arid sites. Despite these limitations, our model may still be extremely useful for global modeling efforts, because it accurately (R²=0.6804) described general patterns of long‐term global decomposition for a wide array of litter types, using relatively minimal climatic and litter quality data.     

The effect of sunlight on leaf litter quality reduces growth of the shredder Klapopteryx kuscheli

• 1 The direct effect of sunlight on the conditioning, breakdown and incorporation of leaf litter in stream food webs has not yet been considered. The aim here was to evaluate the effects of light intensity on the colonization of leaf litter by microorganisms and its resulting quality as food for the stonefly shredder Klapopteryx kuscheli.
• 2 Leaf litter was conditioned for 2 months in an open reach of a second‐order stream in litter bags either exposed to or shaded from direct sunlight. Subsequently, we performed laboratory experiments to test larval consumption, growth, growth efficiency and feeding preference fed on both leaf litter treatments.
• 3 Leaf litter in the unshaded treatment had three times more chlorophyll‐a (Chl‐a) than that in the shaded treatment, 50% lower fungal biomass and similar bacterial abundance. Although larvae did not prefer either food and fed at the same rate on both leaf litter treatments, they grew twice as fast on the shade‐conditioned leaves and attained a two‐fold higher growth efficiency.
• 4 Sunlight can have significant effects on detritus‐based food webs. Riparian modification induced by human activities in forested catchments increases the potential for sunlight to influence detritus dynamics.

     

Cadmium-induced subcellular accumulation of O2·− and H2O2 in pea leaves

Cadmium is a toxic metal that produces disturbances in plant antioxidant defences giving rise to oxidative stress. The effect of this metal on H₂O₂ and O₂^·? production was studied in leaves from pea plants growth for 2 weeks with 50 µm Cd, by histochemistry with diaminobenzidine (DAB) and nitroblue tetrazolium (NBT), respectively. The subcellular localization of these reactive oxygen species (ROS) was studied by cytochemistry with CeCl₃ and Mn/DAB staining for H₂O₂ and O₂^·?, respectively, followed by electron microscopy observation. In leaves from pea plants grown with 50 µm CdCl₂ a rise of six times in the H₂O₂ content took place in comparison with control plants, and the accumulation of H₂O₂ was observed mainly in the plasma membrane of transfer, mesophyll and epidermal cells, as well as in the tonoplast of bundle sheath cells. In mesophyll cells a small accumulation of H₂O₂ was observed in mitochondria and peroxisomes. Experiments with inhibitors suggested that the main source of H₂O₂ could be a NADPH oxidase. The subcellular localization of O₂^·? production was demonstrated in the tonoplast of bundle sheath cells, and plasma membrane from mesophyll cells. The Cd‐induced production of the ROS, H₂O₂ and O₂^·?, could be attributed to the phytotoxic effect of Cd, but lower levels of ROS could function as signal molecules in the induction of defence genes against Cd toxicity. Treatment of leaves from Cd‐grown plants with different effectors and inhibitors showed that ROS production was regulated by different processes involving protein phosphatases, Ca²⁺ channels, and cGMP.     

Cytogenetic Follow-Up in a Case With a Primary Cutaneous Melanoma and Five Metastatic Lesions

Cytogenetic analyses conducted on several cases of melanoma have contributed to the identification of the chromosomal regions where the sequences responsible for malignant transformation and the evolution of this tumor are probably located. With regard to these problems, it is very important to have the possibility to analyze, through the use of cytogenetics, both the primary melanoma and the metastatic lesions from the same patient. We present a case in which the primary melanoma and five different metastases were studied by using cytogenetics. The primary tumor showed an inversion of chromosome 1 where the p36 region, often proposed in literature as the location of a melanoma susceptibility gene, was involved. Three cutaneous and one lymphonodal metastases presented the same nine clonal chromosomal aberrations. In particular, one is a further rearrangement of the marker present in the primary tumor; another is a deletion of the 9p21pter region in which the p16 gene is located. Our results can provide a contribution to the hypothesis of the location of a candidate gene for melanoma in the 1p36 region and can also underscore the role of the 9p21 region in the progression of melanoma.