Nuclear magnetic resonance imaging in studies of gravitropism in soil mixtures

Gravitropic responses of oat coleoptiles were measured in different growth media; humid air, natural soil and artificial soil (glass beads). The oat coleoptiles in soil and glass beads were monitored by NMR imaging, while those in humid air were imaged in darkness with an infrared-sensitive charge-coupled device (CCD) camera. The present study shows for the first time that gravitropic experiments can be performed in artificial soil using NMR imaging as a convenient and suitable recording method. Not only was it possible to follow the gravitropic curvatures in natural soil, but the artificial soil allowed plant images of sufficient spatial and temporal resolution to be recorded. The advantages of using artificial soil in magnetic resonance imaging studies are that the iron content of glass beads is very low compared with natural soil, and that the artificial soil matrix can easily be standardized with regard to particle size distribution and nutrient content. Two types of glass beads were used, the diameter of the small and the large beads being 300–400 and 420–840 μm, respectively. The growth rate of the coleoptiles in soil and in big beads was roughly the same and only slightly lower than in humid air, whereas small beads reduced the growth rate by approx. 16%. The bending rate of the coleoptiles during the gravitropic response was reduced by c. 65% in soil and 75% in bead mixtures relative to bending in air. It should be noted, however, that the maximum curvature of the coleoptile tip was of the same order in all cases, about 35°. This value may represent the largest possible curvature of the organ. The potential of NMR imaging to study how plant organs penetrate the soil under the influence of gravitropism, mechanical impedance and thigmotropism is also discussed.     

Foraging behaviour of bird pollinators on Embothrium coccineum (Proteaceae) trees in forest fragments and pastures in southern Chile

Abstract We investigated the effects of forest patch size on the behaviour of birds feeding on the flower nectar of the proteaceous tree Embothrium coccineum J. R. et G. Forster, which is typically restricted to forest edges in agricultural landscapes in southern Chile. We quantified reproductive parameters of trees (no. inflorescences per branch, total and open flowers per inflorescence) in forest fragments varying from 1 ha (small), to 20 ha (medium) and to >150 ha (large), and in remnant trees in pastures. Visits to flowers by nectar‐feeding birds were recorded during 30‐min observation periods, spread throughout the day during two flowering seasons, November 1992 and 1993 (n = 242 periods overall). Aggressive encounters among flower visitors were recorded in 1992. We expected less visits to trees in pastures and small forest patches because abundances of Embothrium's main pollinators, the flycatcher Elaenia albiceps and the hummingbird Sephanoides sephaniodes, decreased in smaller patches. We found, however, that pollinator visiting rates were negatively correlated with forest patch area and were highest for pasture trees. This trend was largely due a decline in the number of visits by E. albiceps, the main flower visitor, in larger patches. Hummingbird visits did not change with forest patch size. Lower visitation rates to flowering trees in larger forest fragments seemed to be a consequence of territorial defence by E. albiceps and were unrelated to differences in floral display.     

Sayrevilleinae Legalov,a newly recognised subfamily of fossil weevils (Coleoptera,Curculionoidea, Attelabidae) and the use of synchrotron microtomography to examine inclusions in amber

Two genera of extinct weevils, Sayrevilleus Gratshev & Zherikhin from Cretaceous New Jersey amber and Baltocar Kuschel from Eocene Baltic amber, are recognized as close relatives based on similarities revealed by the use of synchrotron tomography and the availability of new amber inclusions. The subfamily Sayrevilleinae Legalov stat. nov. is characterized by possessing mandibles with an external cutting edge and an inner blunt edge. The subfamily is placed in the family Attelabidae (s.l.), although some characters also suggest a possible relationship with the ‘higher weevils’ comprising Caridae, Brentidae, and Curculionidae. Sayrevilleus is transferred from the tribe Auletini of Rhynchitinae to Sayrevilleinae, and Sayrevilleus grimaldii Gratshev & Zherikhin is redescribed. Baltocar Kuschel is transferred from Caridae to Sayrevilleinae and revised, its type species, Baltocar succinicus (Voss), is redescribed and three new species, Baltocar groehni Riedel sp. nov. , Baltocar hoffeinsorum Riedel sp. nov. , and Baltocar subnudus Riedel sp. nov. are described based on eight well‐preserved inclusions. The genera Orapauletes Legalov and Zherichiniletes Legalov previously assigned to Sayrevilleini are regarded as Curculionoidea incertae sedis. The Sayrevilleinae were distributed over areas of North America and Europe at least since the Late Cretaceous (c. 90 Mya) and were probably relatively diverse until the Eocene (c. 44 Mya). It is speculated that they became extinct through competition with Curculionidae, which used a similar oviposition strategy. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 165 , 773–794.     

Morphological and Agronomic Traits of a Wild Population and an Improved Cultivar of Common Bean (Phaseolus vulgaris L.)

Through the process of domestication, bean varieties have beenselected from their wild ancestors for various anthropocentrically-importantcharacteristics. In order to compare some agronomic and morphologicaltraits of a wild population and a modern variety (cv. Bayo Mecentral),the following variables were evaluated: growth habit; numberof nodes on the main stem; number of branches and pods per plant;flower and pod colours; stem length; days to initiation of flowering;days to physiological maturity and duration of flowering. Variationin each trait was recorded, particularly in the wild population.The growth habits of the wild population were very diverse andthere were positive and significant correlations between 13pairs of variables, including the number of nodes on the mainstem, pods per plant, days to flowering and duration of flowering,whereas domesticated beans gave only a few significant correlations.The analysis of principal components indicated that the linearcombination of agronomic and morphological variables, involvingthe first three principal components, accounted for 70% of thetotal variability of the data, and the populations were clearlyseparated as two biological entities by the first principalcomponent. This study confirms that the process of domesticationhas acted to reduce variation in a range of characters. Growth; growth habit; Phaseolus vulgaris ; domestication     

Litter-associated bacteria and fungi – a comparison of biomass and communities across lakes and plant species

1. We investigated the importance of lake water chemistry and substrate properties in regulating microbial decomposer communities on macrophyte litter. Ten lakes of differing water chemistry, including such variables as nutrient concentration, pH and dissolved organic carbon, were sampled in October 2003. Water chemistry was analysed, and litter from the macrophytes Phragmites australis, Schoenoplectus lacustris and Nuphar lutea was collected from both above and below the water surface. 2. The three plant species differed widely in carbon and nitrogen content. The aerial parts of P. australis had highest C : N ratio (mean value 125), while the lowest values were found in leaves of N. lutea (19.8). 3. Fungal carbon ranged from 0.15 to 6.4 mg g^?1 dry weight (DW), and was higher on aerial than on submerged plant parts. Fungal biomass was highest on S. lacustris and lowest on N. lutea. Denaturing gradient gel electrophoresis revealed no differences in the number of fungal taxa between plant species or plant parts, with the limitation that no molecular analysis was possible for N. lutea. 4. In contrast, bacteria were most abundant on N. lutea, but showed no significant difference between leaf and stem parts. The number of bacterial taxa was highest on the submerged parts of P. australis. 5. The correlations between microbial variables and the properties of lakes and litter were analysed using multivariate statistics. In a principal component analysis, litter properties explained 78% of the variation in microbial variables. In contrast, redundancy analysis revealed that the explanatory power of lake water chemistry was only 20%, indicating that the properties of the growth substratum were more important than those of the lake water for the attached microbial communities.     

Analysis of cytosolic and plastidic serine acetyltransferase mutants and subcellular metabolite distributions suggests interplay of the cellular compartments for cysteine biosynthesis in Arabidopsis

In plants, the enzymes for cysteine synthesis serine acetyltransferase (SAT) and O-acetylserine-(thiol)-lyase (OASTL) are present in the cytosol, plastids and mitochondria. However, it is still not clearly resolved to what extent the different compartments are involved in cysteine biosynthesis and how compartmentation influences the regulation of this biosynthetic pathway. To address these questions, we analysed Arabidopsis thaliana T-DNA insertion mutants for cytosolic and plastidic SAT isoforms. In addition, the subcellular distribution of enzyme activities and metabolite concentrations implicated in cysteine and glutathione biosynthesis were revealed by non-aqueous fractionation (NAF). We demonstrate that cytosolic SERAT1.1 and plastidic SERAT2.1 do not contribute to cysteine biosynthesis to a major extent, but may function to overcome transport limitations of O-acetylserine (OAS) from mitochondria. Substantiated by predominantly cytosolic cysteine pools, considerable amounts of sulphide and presence of OAS in the cytosol, our results suggest that the cytosol is the principal site for cysteine biosynthesis. Subcellular metabolite analysis further indicated efficient transport of cysteine, γ -glutamylcysteine and glutathione between the compartments. With respect to regulation of cysteine biosynthesis, estimation of subcellular OAS and sulphide concentrations established that OAS is limiting for cysteine biosynthesis and that SAT is mainly present bound in the cysteine–synthase complex.     

Genetic and phenotypic variation among Galaxias maculatus populations reflects contrasting landscape effects between northern and southern Patagonia

1. Understanding the influence of landscape characteristics on genetic and phenotypic intraspecific variability can yield insights into how evolutionary processes work as well as provide essential information for the conservation of biodiversity. 2. Our aim was to compare the genetic structure and phenotypic variation among Galaxias maculatus populations inhabiting two Atlantic Ocean river basins in Patagonia in relation to historical and contemporary landscape characteristics associated with latitude. 3. Population genetic analysis (based on eight microsatellite loci, 505 individuals) indicates that genetic structure is more pronounced in the Río Negro basin (RN) at 39–41°S (10 localities) than in the southernmost Santa Cruz River basin (SCR) at 49–50°S (seven localities). Spatial autocorrelation analysis showed different effects of geographic distance in shaping population differentiation patterns in the two basins. 4. While in northern Patagonia, fragmented populations could have survived the severity of Quaternary climate cycles, at higher latitudes G. maculatus populations were probably extirpated by extensive ice sheets. Extant populations in the upper reaches of the southernmost basin probably originated from refugia close to the Atlantic Ocean. 5. Based on otolith microchemistry, we have documented facultative diadromy for the first time for the species in the SCR basin, while no evidence of migration to the sea was found in individuals from the RN basin. Vertebral number increased with latitude, and within the SCR basin, the higher counts are possibly associated with a migratory life style.     

The postcranial anatomy of Coloradisaurus brevis (Dinosauria: Sauropodomorpha) from the Late Triassic of Argentina and its phylogenetic implications

Abstract: Basal sauropodomorphs from the Upper Triassic Los Colorados Formation of north‐western Argentina have been known for several decades but most of them are only briefly described. New postrcanial remains of Coloradisaurus brevis, the most gracile sauropodomorph from this unit, are described here and evaluated within a phylogenetic context. These materials belong to a single individual and include elements of the vertebral column, pectoral girdle, incomplete forelimb, pelvis and hindlimb. These elements share an autapomorphic feature with the type specimen of Coloradisaurus brevis and provide novel and unique features that diagnose this taxon, such as pubic apron with semicircular cross‐section and with a depression on its anterior surface, distal surface of the tibia deflected and facing posterodistally and well‐developed pyramidal dorsal process of the posteromedial corner of the astragalus. Several postcranial characters of Coloradisaurus are exclusively shared with Lufengosaurus, from the Lower Jurassic of China. The inclusion of this information in two recent phylogenetic data sets depicts Coloradisaurus as closely related to Lufengosaurus and well nested within Plateosauria. Both data sets used indicate strong character support for the inclusion of Coloradisaurus and Lufengosaurus within Massospondylidae.     

Effect of adults on juvenile reproduction of Calomys venustus (Muridae: Sigmodontinae)

Abstract We tested the hypothesis that adult overwintering Calomys venustus inhibit maturation and reproduction in young‐of‐the‐year from the first cohort. The study was carried out in four 0.25‐ha enclosures (two control and two experimental), each situated on natural pasture. This study was conducted between August 1997 and March 1999 and had two parts: removal of overwintering male (ROM) and removal of overwintering female (ROF). For the ROM treatment overwintering males were removed immediately after the first cohort of juveniles were born, in the ROF treatment overwintering females were removed after the first cohort were weaned. Weekly censuses were taken for three successive days over 6 weeks. The sexual maturation and reproductive condition of juveniles were compared between treatments (overwintering male or female removal) using repeated‐measures anova . The repeated measures factor was the age of juveniles. Removal of overwintering males and females did not affect sexual maturation of juveniles, however, overwintering males influenced the onset of reproductive activity of juvenile females at the beginning of the breeding period.