Effects of copper deficiency on root nodules of subterranean clover

Summary Effects of copper deficiency on the development of subterranean clover root nodules were studied. These included a depression of the bacteroid content, an accumulation of starch in the invaded cells and a reduction in the rate of development of the nodule apex. A similar pattern of increasing severity of metabolic effects in the youngest tissues was also found in leaves, but at a later stage of plant development than in nodules. At low copper supply the copper content of tissues and the activity of known copper-containing enzymes was depressed. The relevance of the observations to the disturbance of metabolism within the low copper nodules was discussed. It was suggested that low activity of copper containing enzymes (e.g. cytochrome c oxidase) might be important for maintenance of low oxygen tension within the nodule cells essential for nitrogen fixing activity. Most of the data in this paper are taken from the thesis submitted by B. Cartwright for the degree of Ph.D. of the University of Nottingham.     

The role of the excision and error-prone repair systems in mutagenesis by fluorinated quinolones in Salmonella typhimurium.

Patterns of reversion produced by ciprofloxacin, enoxacin and ofloxacin in Salmonella typhimurium strains carrying the hisG428 ochre mutation have been studied. These fluorinated quinolones produce a significant increase in reversion of this mutation, even when it is located on the chromosome. Nevertheless, reversion is higher when the hisG428 mutation is on the multicopy plasmid pAQ1 than when it is on the chromosome. Reversion of hisG428 induced by fluorinated quinolones is abolished both in a uvrB genetic background and in the absence of the plasmid pKM101. Therefore, mutagenesis produced by fluorinated quinolones in the Salmonella mutagenicity assay is significantly affected by both the excision repair and the error-prone repair systems. Furthermore, fluorinated quinolones are also detected as moderate mutagens with the base substitution hisG46 mutation when both repair systems are functional in the tester strain.     

Merri Creek: Managing an urban waterway for people and nature

The restoration of Melbourne's Merri Creek demonstrates the potential for achieving environmental improvements through a process that integrates the technical, ecological and social aspects.