The Effect of Light on the Senescence of Detached Cucumber Cotyledons

Measurements of cell constituents of cotyledons of cucumberexcised and kept in the light show differences from those excisedand kept in the dark. These differences are partly resolvedby adding glucose to the water-supply of the cotyledons in thedark suggesting that a lack of photosynthetic products is thecontrolling factor in their senescence. Under other circumstancesdifferent factors are operative suggesting that the first stepin senescence is different under different conditions.     

A rapid electrophoretic method for the measurement of plasmid copy number

A rapid and inexpensive method for the measurement of copy number of small plasmids, ranging from 8.7 to 13 kb, in under 1 ml of liquid culture is described. The method involves whole cell lysis, electrophoretic separation of plasmid and chromosomal DNA followed by relative densitometric measurement of each, to give an estimation of the plasmid copies per chromosome. Results can be obtained in under 8 h and the method proved to be reproducible, fast and ideal for processing large numbers of samples from batch or continuous culture.     

Rapid small scale preparation of bacterial genomic DNA, suitable for cloning and hybridization analysis

The uptake of noxythiolin by a urinary isolate of Escherichia coli was examined initially at 37°C but the adsorption isotherm was complicated by the concomitant degradation of the compound. When drug adsorption was investigated at 4°C, to reduce the degradation rate of the compound, it was observed that noxythiolin was taken up by the urinary isolate in a linear fashion. The resulting adsorption patterns are discussed in relation to their possible classification. The implications of this uptake are considered with respect to the antimicrobial activity of noxythiolin.     

The Yellowing of Attached and Detached Cucumber Cotyledons

Measurements of various constituents and the activities of variousenzymes have been made in attached and detached cotyledons ofCucumis sativus. The complex changes observed suggest that thereis a reproducible pattern. Comparison of results for attachedand detached material shows that, although both become yellow,the other biochemical changes associated with yellowing arenot the same.