Transport and Degradation of Auxin in Relation to Geotropism in Roots of Phaseolus vulgaris

The movement of auxin in Phaseolus vulgaris roots has been examined after injection of IAA^?3H into the basal root/hypocotyl region of intact, dark-grown seedlings. Only a portion of the applied IAA^?3H was transported unchanged to the root tip. The major part of the chromatographed, labelled compounds translocated to the roots was indole-3-acetylaspartic acid (IAAsp) and an unidentified compound running near the front in isopropanol, ammonia, water. The velocity of the auxin transport (7.2 mm per hour) was calculated from scintillation countings of methanol extracts from serial sections of the root. An accumulation of radioactive compounds in the extreme root tip, was observed 5 h after the injection of IAA. The influence of exogenous IAA on the geotropical behaviour of the bean seedling roots was examined. Pretreated roots were stimulated for 5 min in the horizontal position and then rotated parallel to the horizontal axis of the klinostat for 60 or 90 min. The resulting geotropic curvature of IAA-injected and control roots showed significantly different patterns of development. When the stimulation was started 5 h after application of the auxin, the geotropic curvature became larger in roots of the injected plants than in the controls. If, however, the translocation period was extended to 20 h the geotropic curvature was significantly smaller in the roots of the injected plants. The auxin injection did not significally affect the rate of root elongation. The change in geotropical behaviour of the roots is interpreted as a result of the influence of the conversion products of the applied IAA on the geotropical responsiveness.     

Germination and Dormancy of Reed Canary-Grass Seeds (Phalaris arundinacea)

Effects of various chemical and physical factors on the germination of several seed lots of reed canary-grass (Phalaris arundinacea L.) have been studied. Germination at the optimum constant temperatures of 24 to 27°C was significantly stimulated by the following treatments: moist chilling in light, red light given during the first 3 days of imbibition, three 2-h periods at 12°C given during the second day of imbibition, ethylene, increased oxygen tension and soaking in aerated water for 4 days. Dry storage at 20–30°C had no effect on the germination ability of the seeds. No significant quantities of germination inhibitors were found either in water or methanol extracts of seed dispersal units. By comparing three cultivars with various degrees of seed dormancy, respiration measurements showed that there was a significant positive correlation between oxygen uptake prior to visible germination and germination capacity. Similarly, germination-stimulating treatment significantly enhanced oxygen uptake prior to visible germination.     

Phycochrome d, a New Photochromic Pigment from the Blue-Green Alga, Tolypothrix distorta

A new reversibly photochromic pigment, phycochrome d, has been found in extracts of the blue-green alga Tolypothrix distorta. This phycochrome exhibits an absorbance increase in the red region (maximum at about 650 nm) when irradiated with 650 nm light, and a corresponding absorbance decrease when irradiated with 610 nm light. The absorbance difference spectrum and action spectra for in vitro conversions were determined.     

Disturbance mediates the effects of nutrients on developing assemblages of epibiota

Local dynamics such as resource enhancement (e.g. nutrient supply) and stochastic events of destruction (disturbances that provide new space) are hypothesized to counteractively affect species diversity and composition. We tested the independent and interactive effects of nutrients and disturbance on the development of assemblages of epibiota attached to vertical surfaces in an oligotrophic system. Nutrient concentrations were manipulated at three levels (ambient, medium and high) while disturbance was manipulated by removing biomass at seven frequencies (0×, 2×, 3×, 4×, 5×, 7×, 12×). Nutrient and disturbance regimes had opposing effects on diversity such that species richness increased with resource enhancement (nutrients) and declined with disturbance. These results support the model that increased heterogeneity of distribution of limiting resources allows the coexistence of species with low and high resource requirements.     

Recolonization history and large-scale dispersal in the open sea: the case study of the North Atlantic cod, Gadus morhua L.

Most studies of the genetic structure of Atlantic cod have focused on small geographical scales. In the present study, the genetic structure of cod sampled on spawning grounds in the North Atlantic was examined using eight microsatellite loci and the Pan I locus. A total of 954 cod was collected from nine different regions: the Baltic Sea, the North Sea, the Celtic Sea, the Irish Sea and Icelandic waters during spring 2002 and spring 2003, from Norwegian waters and the Faroe Islands (North and West spawning grounds) in spring 2003, and from Canadian waters in 1998. Temporal stability among spawning grounds was observed in Icelandic waters and the Celtic Sea, and no significant difference was observed between the samples from the Baltic Sea and between the samples from Faroese waters. F -statistics showed significant differences between most populations and a pattern of isolation-by-distance was described with microsatellite loci. The Pan I locus revealed the presence of two genetically distinguishable basins, the North-west Atlantic composed of the Icelandic and Canadian samples and the North-east Atlantic composed of all other samples. Permutation of allele sizes at each microsatellite locus among allelic states supported a mutational component to the genetic differentiation, indicating a historical origin of the observed variation. Estimation of the time of divergence was approximately 3000 generations, which places the origin of current genetic pattern of cod in the North Atlantic in the late Weichselian (Wisconsinian period), at last glacial maximum.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 315–329.     

Assessing the taxonomic status of tropical frogs through bioacoustics: geographical variation in the advertisement calls in the Eleutherodactylus discoidalis species group (Anura)

The taxonomic status of a very poorly known group of Andean frogs (the Eleutherodactylus discoidalis group) is assessed through acoustic and statistical analyses of differences in temporal parameters of advertisement calls, such as the number of pulses and the call duration, and also in a spectral parameter, dominant frequency. As these species are usually misidentified or ignored because of their taxonomic complexity in both ecological and biodiversity studies, we provide a bioacoustical diagnosis for each species in order to facilitate identification in the field. Differences in acoustic parameters support the specific status of Eleutherodactylus cruralis , E. discoidalis , Eleutherodactylus ibischi , and Eleutherodactylus madidi . The name E. cruralis is probably applied to three different species: the nominal form from Amazonian forests of the Andean slopes and adjacent lowlands, and two cryptic species restricted to inter-Andean dry valleys and cloud forests from central Bolivia. Moreover, the distribution of energy through the call and the aggregation of pulses seem to be useful meristic characters for detecting interspecific differences. Populations from each macrohabitat can be recognized by distinctive advertisement calls, usually corresponding to a recognized species. For the whole group, pulse rate is significantly correlated to latitude, which could indicate a speciation process along the Andes in relation to habitat changes and isolation. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 353–365.     

Alternative splicing and protein function

Background  

Alternative splicing is a major mechanism of generating protein diversity in higher eukaryotes. Although at least half, and probably more, of mammalian genes are alternatively spliced, it was not clear, whether the frequency of alternative splicing is the same in different functional categories. The problem is obscured by uneven coverage of genes by ESTs and a large number of artifacts in the EST data.     

Capture and commercialization of blue land crabs ("guaiamum") Cardisoma guanhumi (Lattreille, 1825) along the coast of Bahia State, Brazil: an ethnoecological approach

Background

Blue Land Crab (Cardisoma guanhumi) is one of the most important crustacean species captured and commercialized in Brazil. Although this species is not considered to be threatened with extinction, populations of C. guanhumi are known to be rapidly diminishing due to heavy harvesting pressures and degradation of their natural habitats, highlighting the necessity of developing and implanting management and protection strategies for their populations. There have been no ethnozoological publications that have focused specifically on C. guanhumi, in spite of importance of this type of information for developing efficient management plans of resource utilization. So, the present work describes the ethnoecological aspects of the capture and commercialization of C. guanhumi by a fishing community in northeastern Brazil.

Methods

Field work was carried out in the municipality of Mucuri, Bahia in Brazil, between the months of January and March/2011 through the use of open semi-structured interviews with all of the crustacean harvesters in city who acknowledged their work in capturing this species, totaling 12 interviewees. The informants were identified through the use of the "snowball" sampling technique. In addition to the interviews themselves, the "guided tour" technique and direct observations was employed.

Results

According all the interviewees, the C. guanhumi is popularly called "guaiamum" and is collected in "apicum" zones. They recognize sexual dimorphism in the species based on three morphological characteristics and the harvesters also pointed two stages in the reproductive cycle during the year and another phase mentioned by the interviewees was ecdysis. All of the interviewed affirmed that the size and the quantities C. guanhumi stocks in Mucuri have been diminishing. All of the interviewees agreed that the species and other mangrove resources constituted their principal source of income. The harvesters dedicated three to five days a week to collect Blue Land Crabs and the principal technique utilized for capturing is a trap called a "ratoeira" (rat-trap).

Conclusions

The results of the present work demonstrated that the community retains a vast and important volume of knowledge about C. guanhumi that could subsidize both scientific studies and the elaboration of viable management and conservation strategies for this species.