Effects of flue-curing and ageing on the volatile basic constituents of Virginia tobacco

Flue-curing and ageing of Virginia tobacco reduce the amounts of nicotine and several of its transformation products. In contrast, the concentrations of certain structurally simple pyridines and a few compounds, which are presumably products of sugar—amino acid interactions, are found to increase. Generation of several pyridines and a few other bases during the leaf processing is also observed.     

ELIXIR‐EXCELERATE: establishing Europe's data infrastructure for the life science research of the future

A new inter‐governmental research infrastructure, ELIXIR, aims to unify bioinformatics resources and life science data across Europe, thereby facilitating their mining and (re‐)use. Subject Categories: Computational Biology, Methods & Resources, S&S: Ethics

Creating knowledge by connecting and analysing large amounts of life science data is transforming our society, allowing us to start addressing major scientific and societal challenges, such as adaptation to climate change or pathogen outbreaks in an interconnected world. Modern biology is dependent on the generation, sharing and integrated analysis of digital data at scale. A deeper understanding of biological systems is now becoming possible thanks to breakthroughs in technologies that study life systematically at different scales, from molecules and single‐cell pathogens to complex animal or plant models and ecosystems as well as across temporal ranges spanning split‐second reactions to multi‐year clinical or agronomic trials, and beyond. The key to analyse and leverage this complex, fragmented and geographically dispersed life science data landscape is to ensure it is easy to find and reuse by researchers. This article comments on ELIXIR, an international organisation that brings together bioinformatics researchers and life science resources across Europe and integrates them into a single federated infrastructure.     

Simulation of organic shape: The roles of phenomenology and mechanism

Models adducing mechanisms of morphogenesis from observations of geometric similarity between mathematical and natural forms must be rigorously challenged by extensive direct observations of the process being modeled. © 1994 Wiley-Liss, Inc.     

Chemotaxonomy of some problematic palaeozoic plants

Chemical data are given on the remains of nine fossil genera ranging from Precambrian to Carboniferous in age (Chuaria, Sporangites, Taeniocrada, Orestovia, Parka, Protosalvinia, Spongiophyton, Solenites, Botryococcus). It is suggested that such chemical data are useful additional criteria in making taxonomic assignments in palaeontology. Analyses indicate a high level of organic chemical diversity, although the original composition has evidently been altered by temperature and pressure over a long period of time. The labile chemical constituents are retained within a more chemically inert carbon matrix, which shows a progressive alteration of the ratios of C, N, O and H with respect relative age, similar to that seen in the coalification process.The chemical composition of Sporangites specimens is more suggestive of an animal rather than a plant affinity; it is here suggested that this genus represents in part the remains of some animal egg test. Hydrolytic products of Solenites and Taeniocrada indicate the presence of aliphatic hydroxy acids suggesting the presence of cutin and suberin. The chemical compositions of Orestovia, Parka, Protosalvinia, Spongiophyton and Botryococcus are interpreted as being consistent with an algal rather than a vascular plant affinity. Evidence for extreme diagenesis of the acritarch-like Chuaria greatly limits chemotaxonomic consideration. The possible role of thermal and biotic-thermal degradation patterns seen in palaeochemistry is discussed.     

Changes in the factor of safety within the superstructure of a dicot tree

The objective of this study was to determine whether the factor of safety for mechanical stability varied among stems differing in size and age within the superstructure of a large dicot tree. Two factors of safety were selected for study: the quotient of the critical buckling height and the actual length of stems, Hcrit/L, and the quotient of the modulus of rupture (the force per unit area required to break a stem) and the working stress (the force per unit area resulting from the biomass measured distal to a stem), M_R/σ_w. These two dimensionless safety factors were determined for a total of 420 shoot segments comprising much of the aboveground biomass of a Robinia pseudoacacia (Fabaceae) tree measuring 18.7 m in height and 1347 kg in mass, and 0.46 m in diameter (40 yr old) at 1.2 m from the ground. An S-shaped trend was observed when each of the two factors of safety was plotted as a function of stem age. Each factor decreased from a local maximum for the most distal (peripheral) stems in the canopy to a local minimum value for stems ∼10 yr old; each factor increased again to another local maximum for stems 11–18 yr old, and then decreased steadily toward the base of the trunk. This trend was the result of the allometric relationships among stem diameter, length, biomass, and material properties (stiffness and strength) with respect to stem age. Although they were disproportionately more slender than their older counterparts, peripheral stems were sufficiently stiff and strong to sustain the stresses resulting from their weight and that of foliage without deflecting under these loads, yet they were sufficiently flexible to easily bend and thereby presumably provide a mechanism to reduce the drag forces acting on the entire tree. In contrast, the internally imposed mechanical forces acting on progressively older stems increased at a greater rate than the observed rate of increase in stem stiffness, strength, or diameter. The probability of mechanical failure, which must be considered from a demographic perspective (i.e., an age-dependent phenomenon), thus increased from older branches to the base of the trunk. Reports of similar allometric trends based on interspecific comparisons among diverse dicot species comply with the allometry observed for the R. pseudoacacia tree and suggest that the S-shaped trend for the factor of safety holds for stems differing in age drawn from individual trees and for the trunks of conspecifics differing in age drawn from a dense population.     

A new efficient expression system for Bacillus and its application to production of recombinant phytase

A new expression system was developed for Bacillus subtilis.This system uses a shuttle vector (B. subtilis– Eschericia coli) carrying a phosphate starvation-inducible promoter (pst) and on a fed-batch cultivation strategy. The pst-promoter proved to be very strong and retain its tight regulation also when present on a multi-copy plasmid. The expression system developed showed promising results when applied to the production of recombinant Bacillusphytase – phytase activity at the end of cultivation reached 28.7 U ml^–1.     

The chemotaxonomy of Parka decipiens from the lower old red sandstone,Scotland (U.K.)

Chemical analyses of the hydrocarbon, amino acid, and carbohydrate constituents of the fossil remains of Parka suggest the genus is referable to the Chlorophyta. Gas chromatograms of the reproductive and vegetative areas of thalli show a smooth distribution of normal, saturated acids with maxima at C₁₆ and C₁₂, respectively. Esters of organic-soluble compounds isolated from reproductive areas are characteristically longer in their carbon chain-lengths and show higher maxima. Mass spectra of acid mixtures (before esterification) reveal various series of phenyl- and naphthylaromatic acids, phenols, and dicarboxylic acids. Acid hydrolysis indicated the presence of various polysaccharides rich in mannose and glucose, while enzymatic catalysis with α- and β-amylases and cellulase/chitinase mixtures indicate the presence of α-(1 → 4) and β-(1 → 4) glucopyranose linkages suggesting the presence of starch and cellulose, respectively. Gas chromatographic analysis coupled to mass spectroscopy reveal the presence of sterane derivatives (stigmatane and ergostane) associated with representative genera of the Chlorophyta.     

Effects of Rht-dosage on the breaking strength of wheat seedling leaves

We report the effect of the reduced-height alleles Rht1 and Rht2 on the breaking strength and breaking stress of the first foliage leaves of wheat seedlings. Transverse size variables such as blade transverse area and blade width were positively related to the breaking strength and breaking stress of leaves, as was the total wall area of the principal fiber strands. A negative correlation was found for the Rht-dosage with respect to the breaking strength. Because Rht plants had greater transverse dimensions and equal amounts of principal fiber strands compared to wild type, we posit that Rht may affect the mechanical quality of leaf tissues per se. Rht may serve as an example of a simple genetic system that profoundly affects plant morphology, development, and biomechanics.     

DETERMINATE GROWTH OF ALLIUM SATIVUM PEDUNCLES: EVIDENCE OF DETERMINATE GROWTH AS A DESIGN FACTOR FOR BIOMECHANICAL SAFETY

Determinate growth in an organ can reduce the mechanical liability of dynamic wind loadings. This hypothesis was examined for the peduncles of Allium sativum grown under protected and unprotected field conditions and in the glasshouse. The extent to which the lengths of peduncles approach their critical buckling lengths lcr was correlated with the extent to which peduncles were perturbed mechanically. Glasshouse-grown plants that were protected from dynamic loadings (wind or handling) produced peduncles with low ratios of critical to actual peduncle lengths (lcr/1 = 1.11 ± 0.07); field-grown, unprotected plants had lcr/1 = 1.85 ± 0.29; while plants grown in the field but protected from the wind had lcr/1 = 1.29 ± 0.15. Statistical analyses indicated that peduncle length was the only morphometric parameter examined to significantly differ among plants grown under the three conditions. The frequency distributions of critical (buckling) stress for each of the three populations of peduncles differed; that of the unprotected population conformed to a three-parameter Weibull distribution. Allium sativum exhibits thigmomorphogenesis, i.e., mechanical forces influence the extent and nature of organogenesis. Unlike other thigmomophogenetic species, however, the determinate growth of peduncles did not influence peduncle girth or the elastic (Young's) modulus of tissues. Thus, the extent to which vertical growth proceeded determined the design factor for dynamic loading in these reproductive organs. The design (“margin of safety”) factors of A. sativum peduncles grown under the three different conditions and calculated from lcr/1 were remarkably similar to those specified for engineered columns of wood subjected to stress durations differing in magnitude.