Reversal of the Polarity of IAA Transport in the Leaf Sheath Base of Echinochloa colonum

The transport of [2-¹⁴C]IAA and its derived products has beeninvestigated in segments of the leaf sheath base of Echinochloacolonum. Segments orientated vertically in the normal uprightposition transport ¹⁴C basipetally at rates approximately 10times higher that acropetally. In horizontal segments the basipetalrates are lower, being only 1–4 times higher than acropetalrates. Segments orientated vertically in the inverted positiontransport ¹⁴C basipetally at approximately 1/10 of the acropetalrate. ¹⁴C in the receiver discs from vertically orientated segmentswas found to be present predominantly as [2-¹⁴C]IAA and itsderived metabolite. The levels of each of these compounds from upright and invertedvertical segments followed the same pattern as that of theirtotal ¹⁴C content.     

A late Quaternary phylogeography for Metrosideros (Myrtaceae) in New Zealand inferred from chloroplast DNA haplotypes

Because of its remoteness and mid-latitude position, New Zealand lacks access to the tropical climates that might have ensured straightforward survival for frost-sensitive species during glacial times. Nevertheless, the New Zealand lowland flora retains a substantial complement of plants sourced in the tropics. While there have been extinction pulses for elements of the frost-sensitive flora under glacial/stadial regimes, the surviving remnants have been able to recolonize large areas of habitat during successive warm climate periods. Refugia for such species in stadial New Zealand are likely to have been localized and ecologically suboptimal. To examine these relationships we have applied chloroplast DNA sequence data to the investigation of phylogeographical pattern for five endemic species of Metrosideros subg. Metrosideros , a wide-ranging group of mostly frost-sensitive woody plants in New Zealand. The results of this research verify the location of two generally mooted stadial refugia for the country and provide support for the existence of a third. A simple pattern of chloroplast haplotype diversity was recorded in extra-refugial areas, compared with a greater complexity in the vicinity of the identified refugia. This pattern was independently repeated in both main islands. The proposed refugia correspond to contemporary localities of high average winter temperatures. The sharing of chloroplast haplotypes between the different species of Metrosideros examined suggests that there has been a history of repeated hybridization and introgression for these plants, possibly initiated by periods of refugial confinement.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 399–412.     

A simplified 1,10-phenanthroline technique suitable for the determination of dissolved iron in remote sources of water

• 1 A simple technique is described for the determination of dissolved iron in water. It is useful for investigating remote sources and avoids errors due to post-sampling precipitation of hydrated ferric oxides.
• 2 A small sample is added to a mixed 1.10-phenanthroline-i-acetate buffer solution in the field and this‘developed sample” can then be stored for up to 4 weeks before the absorbancc value is read.

     

Cadmium and calcium interactions in the freshwater amphipod Gammarus pulex

SUMMARY. The accumulation of cadmium from an experimental medium by the freshwater amphipod Gammarus pulex is described.
Much of the uptake is internal as opposed to adsorption on the body surface, and after an apparent saturation of the exoskeleton the hepatopancreas becomes an increasingly important site of cadmium storage. The haemolymph cadmium concentration reaches a high level compared with marine crustaceans, achieving a concentration factor (ratio of internal Cd/ external Cd) of 100 after about 60 h uptake.
The cadmium uptake process is severely inhibited after exposure of experimental animals to 0.5 mM 2:4 Dinitrophenol, indicating the mediation of an active process. This fact together with the negative relationship between cadmium uptake rate and the calcium concentration of the animal suggests that cadmium accumulation by this species may be at least partially accounted for by a process of 'accidental' active cadmium uptake, with cadmium substituting for calcium on a calcium regulatory mechanism.
As yet it has not been possible to establish a true stoichiometric relationship between the two metals. Although calcium influx and cadmium uptake (influx) rates are similar over a wide range of external concentrations, calcium influx is clearly inhibited by a low external ratio of cadmium to calcium. This indicates that the relationship between the two metals is far from an equimolar one and the possibility of non-competitive inhibition of calcium influx by cadmium cannot be eliminated.     

THE PRODUCTION OF ANTIBIOTICS IN SOIL

Extracts of the coats of seeds inoculated with Trichoderma viride, Penicillium frequentans or P. gladioli and sown in soil contained antibiotics, identified by paper chromatography as gliotoxin, frequentin and gladiolic acid respectively. Three actinomycetes, Streptoniyces griseus, S. venezuelae and S. nureofaciens failed to produce an antibiotic in the coats of seeds sown in either John Innes potting compost or a calcareous soil.
When uninoculated pea seeds were sown in a soil in which an unintroduced gliotoxin-producing strain of Trichoderma viride was growing vigorously, gliotoxin was detected in the seed coats.