Pyrolysis mass spectrometry of intact and decomposed leaves ofNuphar variegatum andZostera marina,and some archeological eelgrass samples

The chemical composition of leaves and particulate decomposition residues of the water-lilyNuphar variegatum and the eelgrassZostera marina was studied by Curie-point pyrolysis mass spectrometry. The native water-lily and eelgrass were characterised by pyrolysis products of carbohydrates, proteins and several phenolic components. Prolonged decomposition of the waterlily under aerobic and anaerobic conditions resulted in residues with decreased carbohydrate content and an increased content of proteins, N-acetyl aminosugars and lignins. The proteins and N-acetyl aminosugars must be of microbial origin. This process is less pronounced in eelgrass. The composition of native eelgrass, laboratory decomposition residues, ancient dyke samples and old dry eelgrass used as insulation was evaluated using discriminant analysis of the pyrolysis mass spectra. Prolonged aerobic exposure leads to modifications of the polysaccharide structure. Anaerobic exposure leads to an organic matter rich in aromatic and furan residues whereas the incorporation of sulphur is clearly demonstrated. The eelgrass from the ancient dyke was found to be anaerobically digested. Exposure of this eelgrass dyke to atmospheric conditions due to excavation leads to a composition comparable to aerobically digested eelgrass obtained under laboratory conditions. The documented difference in degradability ofZostera marina andNuphar variegatum is thought to be caused by qualitative and quantitative differences in the phenolic components of both plant species.dedicated to Prof. Dr. J. Kistermaker, on the occasion of his 65 th birthday.     

Differential chemical allocation and plant adaptation: A Py-MS Study of 24 species differing in relative growth rate

The chemical composition of leaves of 24 wild species differing in potential relative growth rate (RGR) was analysed by pyrolysis-mass spectrometry. The variation in RGR significantly correlated with differences in chemical composition: slow-growing species were richer in glucan-based polysaccharides and in C16:0 fatty acid, whereas fast growing ones contained more protein (other than those incorporated in cell walls) and chlorophyll, sterols and diglycerides. Other, apparently significant correlations, e.g. for pentose-based hemicellulose and for guaiacyl lignin appeared solely based on a group separation between mono- and dicotyledonous species.Considering the eleven monocotyledonous and thirteen dicotyledonous species separately, correlations were found in addition to the previously mentioned general ones. Within the group of the monocotyledons the low-RGR species were significantly enriched in pentose-based hemicellulose, ferulic acid and (hydroxy)proline-rich cell wall protein and nearly significant in guaiacyl and syringyl lignin, fast-growing species contained more potassium. Within the group of the dicotyledons slow-growing species were enriched in triterpenes and aliphatic wax esters.In general, the monocotyledons contained more cell wall material such as pentose-based hemicellulose, ferulic acid, glucans (including cellulose) and guaiacyl-lignin, and also more aliphatic wax esters, than the dicotyledons. The dicotyledons, on the other hand, contained somewhat more protein than the grasses.Per unit weight of cell wall, the amount of (hydroxy)proline- rich protein in low-RGR species was comparatively low. A higher investment of cell wall proteins to explain the low rate of photosynthesis per unit of leaf nitrogen of slow-growing species as suggested by Lambers and Poorter (1992), therefore, seems unlikely.Abbreviations HPRP (hydroxy)proline-rich protein(s) - LAR leaf area ratio - LWR leaf weight ratio - MVA multivariate analysis - NAR net assimilation rate - PC principal component - PNUE photosynthetic nitrogen use efficiency - PyGCMS pyrolysis-gas chromatography-mass spectrometry - PyMS pyrolysis mass spectrometry - RGR relative growth rate - SLA specific leaf area - SLM specific leaf mass     

What sources of organic carbon drive food webs in billabongs? A study based on stable isotope analysis

We used the stable isotopes of carbon and nitrogen to examine the food webs of three small flood-plain lakes (billabongs) in south-eastern Australia. With few exceptions, stable carbon isotope analysis could not be used to discriminate among the conspicuous potential sources of fringing, emergent or floating vegetation or benthic detritus. These primary sources showed little spatial or temporal variation in ¹³C values, with means ranging from-28.5 to-26.8 in spring and-29.1 to-25.4 in late summer. Submerged vegetation had similar ¹³C values to the above sources in spring but showed greater spatial variation and were less ¹³C-depleted, considerably so in some species, in late summer. Epiphytes and algae were ¹³C-depleted in spring compared with the other primary sources but became more ¹³C-enriched in late summer. Mean ¹³C values for primary and secondary consumers were not only far more variable (-37.4 to-22.7) but in general were more negative than the potential food sources, particularly in spring. Using the combined information from stable carbon and nitrogen isotope analysis, we could narrow down the list of potential primary sources driving food webs in these billabongs. The freshwater crayfish (Cherax) was one of the few taxa that appeared to obtain its biomass carbon from detrital material. Gastropods and leptocerid caddis larvae on emergent or submerged vegetation obtained a mixture of carbon from epiphytes and macrophytes; in both taxa, epiphytes contributed more to biomass carbon than did the macrophytes. However, other common grazers and collector/gatherers sampled from macrophytes, e.g. baetid mayflies, chironomid larvae and atyid shrimps, were often too ¹³C-depleted even to have derived their biomass carbon solely from epiphytes. Many other primary consumers, including zooplankton, and mussels (Velesunio), and most of the secondary consumers, including water mites (Hydracarina), phantom midge larvae (Chaoborus) and fish, were also ¹³C-depleted. The enormous biomass of littoral and fringing vegetation could contribute to metazoan food webs in these billabongs only if an additional highly ¹³C-depleted source was consumed simultaneously. Methane released from billabong sediments could provide such a ¹³C-depleted carbon source that is re-introduced into metazoan food webs via the consumption of methanotrophic bacteria. Alternatively, food webs in these water bodies are largely driven by an unknown and inconspicuous ¹³C-depleted primary producer, such as planktonic Chlorophyta.     

The phytochrome gene family in grasses (Poaceae): a phylogeny and evidence that grasses have a subset of the loci found in dicot angiosperms

The phytochrome nuclear gene family encodes photoreceptor proteins that mediate developmental responses to red and far red light throughout the life of the plant. From studies of the dicot flowering plant Arabidopsis, the family has been modeled as comprising five loci, PHYA- PHYE. However, it has been shown recently that the Arabidopsis model may not completely represent some flowering plant groups because additional PHY loci related to PHYA and PHYB of Arabidopsis apparently have evolved independently several times in dicots, and monocot flowering plants may lack orthologs of PHYD and PHYE of Arabidopsis. Nonetheless, the phytochrome nucleotide data were informative in a study of organismal evolution because the loci occur as single copy sequences and appear to be evolving independently. We have continued our investigation of the phytochrome gene family in flowering plants by sampling extensively in the grass family. The phytochrome nuclear DNA data were cladistically analyzed to address the following questions: (1) Are the data consistent with a pattern of differential distribution of phytochrome genes among monocots and higher dicots, with homologs of PHYA, B, C, D, and E present in higher dicots, but of just PHYA, B, and C in monocots, and (2) what phylogenetic pattern within Poaceae do they reveal? Results of these analyses, and of Southern blot experiments, are consistent with the observation that the phytochrome gene family in grasses comprises the same subset of loci detected in other monocots. Furthermore, for studies of organismal phylogeny in the grass family, the data are shown to provide significant support for relationships that are just weakly resolved by other data sets.      

Variations in the fluorescence intensity of intact DAPI-stained bacteria and their implications for rapid bacterial quantification

J. ROSS, P.I. BOON, R. SHARMA AND R. BECKETT. 1996. As current techniques for the quantification of bacteria are laborious and often imprecise, instrumental approaches such as sedimentation field-flow fractionation (SdFFF) are attractive. In this technique, fluorogenic dyes specific for nucleic acids are used to identify bacterial cells. Bacterial biomass can be quantified directly with SdFFF if the specific fluorescence of bacterial cells is constant. The effect of different growth conditions on the specific fluorescence of one strain each of Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis and Staphylococcus epidermidis stained with 4',6-diamidino-2-phenylindole was examined. Specific fluorescence varied over a 500-fold range, from 0.22 to 103 arbitrary fluorescence units per cell. Specific fluorescence was highest when cells were in log phase, and lowest when cells were in stationary phase. Specific fluorescence decreased when cells harvested in log phase were starved for 7 d in a carbon-free minimal medium, and increased rapidly (within 2 h) after cells were relieved from carbon limitation. Such variations in specific fluorescence must be considered when using gross fluorescence as a direct indicator of bacterial numbers in the SdFFF technique for quantifying bacterial biomass. Moreover, they have serious implications for the application of fluorescence techniques in other instrumental approaches for bacterial enumeration in environmental samples.     

Safe biotechnology. 8. Transport of infectious and biological materials

The transport of infectious and biological material is regulated by a number of international organizations. This mini-review has been compiled to increase awareness within the scientific community of problems caused by differences in terminology (such as infectious materials/substances, biological products, diagnostic specimens, genetically modified microorganisms) and certain technical aspects of the main international guidelines, and to assist policy makers in the creation of harmonized guidelines. A list of relevant Internet resources has been compiled. Received: 3 March 1997 / Accepted: 8 March 1997     

Different ratios of sucrose/raffinose-induced membrane depolarizations in the mesophyll of species with symplasmic (Catharanthus roseus, Ocimum basilicum) or apoplasmic (Impatiens walleriana, Vicia faba) minor-vein configurations

In mesophyll cells of species with a symplasmic (Ocimum basilicum, Catharanthus roseus, Magnolia denudata) or an apoplasmic (Vicia faba, Impatiens walleriana, Bellis perennis) minor-vein configuration, membrane depolarizations in response to 20 or 200 mol·m^–3 raffinose and sucrose were measured. Ageing period and resting potential marginally affected the degree of depolarization. The symplasmic species showed similar depolarization responses to 20 and 200 mol·m^–3 sucrose or raffinose. In the apoplasmic species, depolarization increased statistically significantly from 20 to 200 mol·m^–3 sucrose, whereas the depolarization response to raffinose was equal at both concentrations. In the apoplasmic species, moreover, the depolarization response to raffinose was significantly weaker than to sucrose at all concentrations. A major difference between symplasmic and apoplasmic species seems to lie in the scantiness of raffinose carriers in the mesophyll plasma membrane of species with the apoplasmic mode of phloem loading.Abbreviations 20R(200R) 20(200) mol·m^–3 raffinose - 20S(200S) 20(200) mol·m^–3 sucrose     

Rapid evolution in a conserved gene family. Evolution of the actin gene family in the sea urchin genus Heliocidaris and related genera

Camarodont sea urchins possess a rapidly evolving actin gene family whose members are expressed in distinct cell lineages in a developmentally regulated fashion. Evolutionary changes in the actin gene family of echinoids include alterations in number of family members, site of expression, and gene linkage, and a dichotomy between rapidly and slowly evolving isoform-specific 3' untranslated regions. We present sequence comparisons and an analysis of the actin gene family in two congeneric sea urchins that develop in radically different modes, Heliocidaris erythrogramma and H. tuberculata. The sequences of several actin genes from the related species Lytechinus variegatus are also presented. We compare the features of the Heliocidaris and Lytechinus actin genes to those of the the actin gene families of other closely related sea urchins and discuss the nature of the evolutionary changes among sea urchin actins and their relationship to developmental mode.