Sodium and potassium relations of Spergularia marina following N and P deprivation: results of short-term growth studies

In this, we consider the coordination of plant growth and ion acquisition, reporting the short-term adjustments of growth and K⁺ and Na⁺ relations which follow when plants are subject to a sudden deprivation of N and P. The plant used for the experiments, Spergularia marina (L.) Grieseb., is a small coastal halophyte, and the growth medium was 0.2 × modified seawater. By considering nutrients whose availability has not been changed, we report on an aspect of organismal integration which has received little attention either experimentally or in mathematical models. The studies are limited to the first 60 h after N and P deprivation in order to consider changes that, if they are not primary responses, are not temporally remote, passive adjustments. For growth analyses, plants were used approximately 30 days after germination and 16 days after transfer to solution culture. Random harvests were made at hourly invervals, and after 12 h, one-half of the plants were transferred to cultures without N or P. Tissue analyses were used to calculate relative growth rates, relative accumulation rates and net uptake rates. For comparison, isotope uptake studies using ⁴²K⁺ and ²²Na⁺ were conducted at 12, 36 and 60 h after deprivation. The effects on growth and biomass allocation were very rapid, detectable within 13 h. K⁺ transport also responded quickly, and from the beginning of the study, there was essentially no net translocation of K⁺ to the shoot. Isotope studies confirmed the responsiveness, with translocation reduced 33 and 90% after 12 and 36 h, respectively. Though Na⁺ adjustments were slower, they were coordinated with growth such that tissue concentrations in the N and P-deprived plants were comparable to those in the controls. We conclude that N and C are insufficient elements on which to build mathematical models useful to environmental physiologists. At a minimum, the incorporation of K⁺ relations in growth models would both allow the development of the osmotic potential needed to drive cell expansion, and provide a means to probe –experimentally as well as mathematically – the coordinating mechanisms of plant growth and resource management.     

SYSTEMATIC ANALYSIS OF SPHAEROPLEA (CHLOROPHYCEAE)1

A systematic investigation of the genus Sphaeroplea was conducted using cladistic analyses of both structural and isozyme characters for the same set of taxa. The structural data were not able to fully resolve some of the taxa while the isozyme data did produce a tree in which all nodes were supported by data. The structural characters were relatively consistent with one another, whereas the isozyme characters were much less internally consistent. Results from independent, cladistic analyses of both data sets support the concept that among those Sphaeroplea species investigated, S. fragilis Buchheim et Hoffman had an early divergence. The two data sets differed primarily in that the structural data support monophyly of the genus Sphaeroplea and the isozyme data do not. The greater relative consistency of the structural data suggests better support for trees inferred from its analysis. Furthermore, searches for character congruence between the two data sets revealed isozyme data which support monophyly of the genus Sphaeroplea, but had been overwhelmed by conflicting isozyme characters.     

Endo's stress analysis of the primate skull and the functional significance of the supraorbital region

A review of Endo's experimental and theoretical procedures and data indicates that the magnitude of the principal strains in the glabella region of both humans and gorillas are low as compared to other parts of the face. Therefore, his data do not provide support for the hypothesis that the glabella region is a highly stressed region during biting. In addition, increased levels of strain in the supraorbital region are directly related to increased levels of masticatory muscle and reaction forces, and not necessarily to anterior tooth loading as opposed to posterior tooth loading. His data also indicate that the supraorbital region in extant humans cannot be accurately modeled as a beam. These conclusions either differ from those of Endo or are not clearly presented or emphasized throughout any of Endo's papers. Therefore, we suggest that a number of investigators have made unsupported or erroneous conclusions based on Endo's work. This is particularly true for those studies that have emphasized the existence of powerful bending stress in the glabella region during incisor biting in both humans and non-human primates.     

History of sedentary farming in Ångermanland, northern Sweden, during the Iron Age and Medieval period based on pollen analytical investigations

Compared with most parts of Europe, northern Sweden is essentially a sparsely populated wilderness. There is, however, an ever increasing body of archaeological and palaeoecological information that shows that the region has a long cultural history. In this paper, results of pollen analytical investigations from four lakes with varved lake sediments, in the province of Ångermanland, are presented. These investigations have yielded evidence of continuous and sedentary agriculture from the 6th century in the region close to the Bothnian coast and near the mouth of the large river Ångermanälven. This early agriculture appears to have been based on animal husbandry and cereal, mainly barley, cultivation. During a second farming expansion phase at ca. A.D. 1200, rye cultivation became more important. The increased farming activity during this period was most pronounced at the coast and in the river valley, but more peripheral regions away from the river valley were also exploited. During the period A.D. 1600–1800, arable farming assumed greater importance. In the first decades of the 20th century, the area under cultivation declined, cereal cultivation mostly ceased and the fields were used for pasture.     

Spatial patterns in a two-tiered semi-arid shrubland in southeastern Spain

Abstract. Single species and bivariate distribution patterns in a semi-arid shrubland in southeastern Spain, dominated by the tall leguminous shrub Retama sphaerocarpa, were investigated by second-order spatial analysis based on Ripley's K-function. Shrubs were significantly clumped because of a strong association of dwarf shrubs, mostly Artemisia barrelieri, under the canopy of Retama. Retama shrubs were randomly distributed, but when different size-classes were analysed separately, the pattern changed from significantly clumped to random and then to regular with increasing canopy diameter, suggesting increasing intraspecific competition with shrub size. Artemisia was significantly clumped at all scales because of aggregation under the canopy of large Retama shrubs. The association between the species became stronger with increasing canopy diameter of Retama shrubs, suggesting that facilitation prevailed over interspecific competition because of niche separation in different tiers, both above and below ground. Retama shrub size thus determined both the type of pattern for its own size class and tier, and the scale and intensity of the association with its understorey shrubs.     

Enlarged Similarity of Nucleic Acid Sequences

The concept of nucleic acid sequence base alternations is presented.The number of base alterations for the sequences of differentlength is established. The definition of "enlarged similarity"of nucleic acids sequences on the basis of sequence base alterationsis introduced. Mutual information between sequences is usedas a quantitative measure of enlarged similarity for two comparedsequences. The method of mutual information calculation is developedconsidering the correlation of bases in compared sequences.The definitions of correlated similarity and evolution similaritybetween compared sequences are given. Results of the use ofenlarged similarity approach for DNA sequences analysis arediscussed.     

Towards an understanding of the relations between tree nutrition,nutrient cycling and environment

The paper contains a discussion of the interrelations between the sciences used by managers of forest land to improve their management, in particular with respect to the plant nutrient economy of the forest ecosystems. Both site studies and studies of nutrient cycling have been carried out for long periods without proper consideration of tree nutrition. Therefore these studies contributed less to the understanding of the role of nutrients as regulators of processes in ecosystems than might have been expected. This situation has improved, especially within the last decade. In addition the necessity to manage forest land for environmental values as well as for forest yield requires new interdisciplinary approaches in the study of the roles of plant nutrients in the forest. Even more branches of biological and environmental sciences than those just mentioned must be involved.     

Barley anther culture using membrane rafts

When compared to agarose solidified media in small petri dishes, membrane rafts used in conjunction with liquid induction media significantly improved anther culture response in the Australian, malting-quality, spring barley cultivar Clipper. In contrast, the German cultivar Gimpel did not show an increased response on rafts.Abbreviations BA 6-benzylaminopurine - IAA indoleacetic acid - DH doubled haploid     

Bioreactors for surface-immobilized cells

Surface immobilization of plant cells avoids the problem of hydrodynamic or shear stress, which tends to be characteristic of suspended cells cultured in typical, mechanically agitated bioreactor systems. Surface immobilization also promotes the natural tendency for plant cells to aggregate, which may improve the synthesis and accumulation of secondary metabolites. In addition, exchange of medium is made simple in surface-immobilized systems, and extracellular secondary products are easily recovered on a continuous basis. However, problems related to regulation of the thickness of the immobilized cell layer, maintenance of the biomass in a productive condition, and vacuolar retention of secondary products have yet to be resolved satisfactorily. This review focusses on two surface-immobilization technologies, differing primarily in the nature and the configuration of the inert support. Prototypes of these designs have been applied to a variety of plant cell systems at bioreactor volumes up to 20 litres. Results obtained with several alternative technologies are also summarized.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - SIPCB surface-immobilized plant cell bioreactor National Research Council of Canada publication no. 38460     

Transport of bacterial inoculants through intact cores of two different soils as affected by water percolation and the presence of wheat plants

Abstract Water flow-innduced transport of Burkholderia cepacia strain P2 and Pseudomonas fluorescens strain R2f cells through intact cores of loamy sand and silt loam field soils was measured for two percolation regimes, 0.9 and 4.4 mm h⁻¹, applied daily during 1 hour. For each strain, transport was generally similar between the two water regimes. Translocation of B. cepacia , with 4.4 mm h⁻¹, did occur initially in both soils. In the loamy sand soil, no change in the bacterial distribution occurred during the experiment (51 days). In the silt loam, B. cepacia cell numbers in the lower soil layers were significantly reduced, to levels at or below the limit of detection. Transport of P. fluorescens in both soils also occurred initially and was comparable to that of B. cepacia . Later in the experiment, P. fluorescens was not detectable in the lower soil layers of the loamy sand cores, due to a large decrease in surviving cell numbers. In the silt loam, the inoculant cell distribution did not change with time. Pre-incubation of the inoculated cores before starting percolation reduced B. cepacia inoculant transport in the loamy sand soil measured after 5 days, but not that determined after 54 days. Delayed percolation in the silt loam soil affected bacterial transport only after 54 days. The presence of growing wheat plants overall enhanced bacterial translocation as compared to that in unplanted soil cores, but only with percolating water. Percolation water from silt loam cores appeared the day after the onset of percolation and often contained inoculant bacteria. With loamy sand, percolation water appeared only 5 days after the start of percolation, and no inoculant bacteria were found. The results presented aid in predicting the fate of genetically manipulated bacteria in a field experiment.