Aluminium-induced changes in the surface and micropore properties of wheat roots: a study using the water vapor adsorption-desorption technique

The geometric and energetic characteristics of root surfaces of two wheat (Triticum L.) varieties, Al tolerant (Inia 66/16) and Al sensitive (Henika), were estimated from experimental water vapor adsorption–desorption data. Roots stressed for around 1 week at pH 4 without and with a toxic aluminium level (0.741 mol m^–3) were studied at the tillering and shooting stages. Roots grown continuously at pH 7 were taken as control. The surface properties of the pH 4 stressed roots were apparently the same as those of the control roots whatever the root age. For the roots of both varieties, the surface area and total micropore volume increased markedly after aluminium treatment. The average micropore radius increased significantly for the sensitive wheat, whereas it increased only slightly for the resistant one. Under Al treatment the number of large pores increased while small pores were fewer for both plants, indicating a possible alteration of the build-up of root tissue. The root surface pores were fractal. The fractal dimension of the sensitive wheat roots decreased under Al treatment, whereas for the resistant wheat this remained apparently unchanged. The adsorption energy distribution functions had different shapes for the sensitive and the resistant wheat varieties: the sensitive variety had greater number of high energy adsorption centers, which implies that the root tolerance on Al stress may be connected with lower polarity of the surface.     

Food collection and response to pheromones in an ant species exposed to electromagnetic radiation

We used the ant species Myrmica sabuleti as a model to study the impact of electromagnetic waves on social insects' response to their pheromones and their food collection. We quantified M. sabuleti workers' response to their trail, area marking and alarm pheromone under normal conditions. Then, we quantified the same responses while under the influence of electromagnetic waves. Under such an influence, ants followed trails for only short distances, no longer arrived at marked areas and no longer orientated themselves to a source of alarm pheromone. Also when exposed to electromagnetic waves, ants became unable to return to their nest and recruit congeners; therefore, the number of ants collecting food increases only slightly and slowly. After 180 h of exposure, their colonies deteriorated. Electromagnetic radiation obviously affects social insects' behavior and physiology.     

Minimum area requirements of breeding birds in fragmented woodland of Central Argentina

The breeding avifauna of 25 woodland fragments (0.85–280 ha) was studied between 1996 and 2004 in Córdoba, Argentina. A distinctive feature of the avifauna of the fragments studied is the low area requirement of most of the species. Of the 54 woodland species recorded, 32 (59.3%) require c . 1 ha and 43 (79.6%) needed no more than 3 ha. Also noticeable is the relatively high number of individuals of most of the species. Both characteristics suggest a good tolerance to fragmentation. However, nine species (16.7%), the area-sensitive species, need fragments of 80 ha or larger. Moreover, eight resident species have apparently become extinct in the fragments that were studied, including the five large species that originally inhabited the area. Proportional odds and log linear models were fitted to relate the minimum area requirements of these species to various ecological characteristics (body size, diet, habitat use, migratory status, and nest type). Closed nesters, resident, woodland exterior, and medium-size species were the groups requiring larger areas. No apparent pattern was observed between area requirements and diet. A recent law prohibits woodland removal, which is a positive step towards the conservation of the fragments. The results suggest that as long as the present amount of woodland is maintained, the situation of the avifauna of the fragments is relatively secure, at least in the short term.     

Capturing ecological complexity: OCI,a novel combination of ecological indices as applied to benthic marine habitats

The novel Overall Complexity Index (OCI) is proposed to measure ecological complexity, incorporating four complexity indices: (1) exergy and (2) throughput as extensive metrics, (3) specific exergy and (4) information as intensive metrics. Exergy and specific exergy estimate structural complexity while throughput and information functional complexity. OCI was applied to benthic habitats in a coastal marine tract encompassing a Marine Protected Area (MPA) in north-western Italy. The four individual indices did not always show homogeneous results in assigning complexity to different habitats. On the contrary, the additive measure provided by OCI showed that seagrass meadows and coralligenous reefs are in all the most complex habitats. Applying OCI provided results consistent with traditional approaches based on expert judgement, which usually attach more interest to seagrass meadows and hard bottoms with respect to soft bottoms, but expressed a synthetic, objective and quantitative approach. OCI can be mapped for management purposes, resolving the discordances evidenced by the individual indices. Ecological complexity in the study area is concentrated in some hot spots, as mapped by OCI, while the greatest part of the seafloor is occupied by low complexity habitats. Only some of these complexity hotspots are included within the Marine Protected Area, while this study suggests that high complexity areas, adjacent to the existing MPA, should be considered for protection possibly reshaping MPA's limits.     

Spectrum structures and biological functions of 8-mers in the human genome

The spectra of k-mer frequencies can reveal the structures and evolution of genome sequences. We confirmed that the trimodal spectrum of 8-mers in human genome sequences is distinguished only by CG2, CG1 and CG0 8-mer sets, containing 2,1 or 0 CpG, respectively. This phenomenon is called independent selection law. The three types of CG 8-mers were considered as different functional elements. We conjectured that (1) nucleosome binding motifs are mainly characterized by CG1 8-mers and (2) the core structural units of CpG island sequences are predominantly characterized by CG2 8-mers. To validate our conjectures, nucleosome occupied sequences and CGI sequences were extracted, then the sequence parameters were constructed through the information of the three CG 8-mer sets respectively. ROC analysis showed that CG1 8-mers are more preference in nucleosome occupied segments (AUC > 0.7) and CG2 8-mers are more preference in CGI sequences (AUC > 0.99). This validates our conjecture in principle.     

Plant functional trait variation in relation to riparian geomorphology: The importance of disturbance

This study examined the patterns of plant functional trait variation in relation to geomorphology, disturbance and a suite of other environmental factors in the riparian margin of the Upper Hunter River, New South Wales, Australia. Vegetation was surveyed on three geomorphic surfaces (point bar, bench and bank) along a 5.5‐km stretch of the Upper Hunter River. Functional traits relating to plant growth and reproduction were collected for the identified species. anova and principal components analysis were used to compare the trait assemblages of species associated with each geomorphic unit. Pearson's correlation coefficients were used to investigate trait variation with respect to environmental variables. There were clear differences in the plant functional trait assemblages associated with the three geomorphic units. Generally the point bar was associated with species that were herbaceous, with small seed mass, a short stature and a high specific leaf area (SLA). Conversely, the bench was associated with grasses that had unassisted seed dispersal and intermediate seed mass and SLA, while species on the bank had tall stature, large seed mass, a high SLA and a perennial life cycle. Variation along the primary gradient of plant functional trait composition was most strongly related to disturbance frequency and to a lesser extent soil nutrients and the proportion of clay and silt, while variation along the secondary gradient was associated with variation in substrate texture as well as soil nutrients.