Subcellular Distribution of Inorganic Phosphate, and Levels of Nucleoside Triphosphate, in Mature Maize Roots at Low External Phosphate Concentrations: Measurements with 31P-NMR

Maize plants were grown in nutrient solution without phosphate,or in which inorganic phosphate (Pi) was maintained at nearlyconstant concentrations of 1 µM, 10µM or 0·5mM. In vivo ³¹P-NMR measurements showed that there was no discernibledifference in the cytoplasmic Pi content (µmol cm^–3root volume) of the mature roots of plants exposed to 1 µM,10µM or 0·5 mM external phosphate for up to 12d. However, the vacuolar Pi content of the mature roots variedabout 10-fold between these three groups. The cytoplasmic Pi content of roots receiving no external phosphatedecreased significantly after about 7 d total growth, and atabout this time the vacuolar pool of Pi became too small foraccurate measurement. The presence of 1 µM Pi in the nutrientsolution completely prevented this decline in cytoplasmic Pi,and there was some evidence that it also raised the Pi contentof the root vacuoles above the almost undetectable level foundin the totally P-starved roots. During the first 7–9 d of growth, the nucleoside triphosphatecontent of the mature roots was unaffected by the concentrationof phosphate in the nutrient solution. The results highlight the close control of cytoplasmic concentrationsof certain important phosphorus metabolites in roots growingin soil of normal agricultural fertility. Key words: Vacuole, cytoplasm, intracellular compartmentation, NTP, P-nutrition     

A multivariate approach to the selection of biological reserves

Multivariate analysis provides an effective context for the examination of some significant aspects of biodiversity and conservation. The framework is a multidimensional space that integrates sample sites, taxa and environments. This approach enables terms such as representativeness, complementarity and irreplaceability to be integrated within an intuitive and practical framework for reserve design. Cluster analysis is proposed to determine what is there by defining a set of complementary clusters. These clusters are sampled in a representative manner; from the core outward. The degree of irreplaceability of a site is defined as the multivariate distance of each potential reserve site to its nearest neighbour.     

库蠓属的两个新种(双翅目:蠓科)

1982年在四川省采集吸血蠓时,发现库蠓属(culicoides)两个新种。现记述如下。新种模式标本分别保藏于四川省成都铁路局中心卫生防疫站和中国科学院动物研究所。     

Taxonomy and Description of Vibrio fluvialis sp. nov. (Synonym Group F Vibrios, Group EF6)

A numerical taxonomic study has been carried out to establish the relationship of group F to other biochemically similar organisms within the family Vibrionaceae. A total of 154 strains were examined including 59 of group F. Out of 114 characters determined for each strain 100 were used to compute average Euclidean distances between strains. Four methods of clustering were used, all of which gave very similar results.
Strains resembling Vibrio anguillarum fell into clusters corresponding to V. anguillarum, Beneckea nereida and a previously unrecognized group, phenon 5. Strains of the Aeromonas hydrophila/punctata group formed a heterogenous phenon within which certain subdivisions, perhaps artificial, could be discerned.
Group F strains all fell in one closely-knit cluster distinct from all the species of Vibrio, Aeromonas, Plesiomonas and Photobacteriwn studied. Group F strains could be divided into two biovars, I and II. Both biovars are present in aquatic, particularly estuarine, environments throughout the world but biovar I strains have also been isolated from humans with diarrhoea. It is concluded that group F is a synonym of group EF6 and that the strains within these groups should be classified in a new species named Vibrio fluvialis. The type strain is NCTC 11327.