Fluorouracil and the isolation of mutants lacking uridine phosphorylase in Escherichia coli: location of the gene

Summary A selective technique is described for the isolation of mutants of Escherichia coli lacking uridine phosphorylase and the location of the gene specifying this enzyme on the bacterial chromosome is determined. Using strains with appropriate lesions it is shown that there are three routes via which 5-fluorouracil can be converted to compounds which inhibit cell growth.     

A note on the nomenclature of two European cockles

The confused nomenclature concerning two European cockles is discussed. Reasons are given to support the genus name Cerastoderma in preference to Cardium and the use of the specific name glaucum in place of lamarcki.
It is concluded that the correct names of the two cockles under discussion are Cerastoderma edule (L.) and Cerastoderma glaucum (Poiret).     

Transport of abscisic acid

The transport of abscisic acid in cotyledonary petiole sectionsof cotton seedlings was investigated using (2-¹⁴C)-ABA in adonor-receiver system. Using the intercept technique, a transportvelocity of 22.4 mm/hr was determined. This velocity was foundto be independent of the length of the petiole or of the concentrationof ABA applied. In a 24-hr period 70% of the applied ABA movedthrough the tissue sections. No polarity was found in any ofthe studies. The capacity of the transport system decreased with increasingage of the tissue and with increasing time of pre-exposure toABA. When metabolism of the tissue was restricted by cold temperature,low-O₂ tension or DNP treatment, transport was inhibited 80to 98%.The distribution of ABA in the petiole during transportwas also investigated. The results are discussed in relationto the well-studied transport of IAA and in relation to thephysiologicalrole of ABA. ¹ Present address: Stanford Research Institute-Irvine, 19722Jamboree Blvd., Irvine, Calif. 92664, U.S.A. (Received November 30, 1970; )     

Effect of ethylenediamine di (o-hydroxyphenylacetic acid) application to soil columns on the distribution of certain nutrient elements in the water-soluble,acid-soluble and exchangeable forms

Summary The chemical behaviour of the sodium form of ethylenediamine di(o-hydroxyphenylacetic acid), Na₂EDDHA, in a calcareous soil column was studied. The results show loss about 2/3 of the synthetic chelate in the soil, possibly due to microbial decomposition and/or fixation of EDDHA. The application of Na₂EDDHA caused an increase in the amount of water-soluble forms of certain elements in the following decreasing order: Fe, Cu, Mn, Ni, Zn and Ca. The increase in the water-soluble forms of such elements is due possibly to the chelation of their insoluble compounds in the soil. The solubilization effect of Na₂EDDHA and the subsequent movement of the elements in the soil solution resulted in a significant decrease in their amounts in the exchangeable and acid-soluble forms in the soil. In conclusion, the synthetic chelate of EDDHA underwent chemical reactions in the soil and caused changes in the ratio of certain elements in the various chemical forms. Sen. author, formerly graduate student at the University of Arizona, now Assistant Professor, University of Ain-Shams, Cairo, Egypt. Jr. author, Vice Chancellor, University of Wisc.-Green Bay.     

Relationship between root cationexchange capacity and sodium tolerance of different crops

Summary Paragrass, wheat, barley, gram, lady's finger, and dhaincha were grown in a soil whose ESP had been adjusted to 1.7, 30.2, 41.4, 58.4, and 77.9. The growth in terms of dry weight of tops and roots decreased with increasing levels of exchangeable sodium percentage (ESP). The sodium-tolerance index was the highest in paragrass (lower-root CEC) followed by barley and wheat (medium root CEC). Dhaincha, gram, and lady's finger (high root CEC) were relatively sensitive crops having low sodium-tolerance index. Fifty per cent reduction in the yield of wheat, barley, paragrass, lady's finger, dhaincha and gram occurred when ESP was 41, 43, 55, 35, 37, and 36, respectively. Increasing ESP of the soil was associated with increasing Na and decreasing Ca, Mg, and K contents of the tops and roots.     

Nuclear and Cell Division in Filamentous Bacteria

GROWTH in unicellular bacteria usually takes place as a sequence of events culminating in cell division^1–6. In some cases, however, bacteria grows in chains (referred to here as filaments). Two reasons have been put forward for this: either the individual segments of a filament are complete cells in which the timing of separation from adjacent segments is an imprecise event, not coordinated with overall growth, or the production of filaments may be a controlled process which is a prerequisite to cell division. There is some support for the first possibility⁷, but more recently it has been observed that the chain length of filamentous bacteria depends on the growth medium^8,9. Here we report further evidence that in the bacterium Bacillus subtilis the production of filaments of up to sixteen nuclei is part of a programme of events necessary for the maintenance of particular rates of cell division and that the structure and physiology of this bacterium can be explained along the same lines as those of the models describing growth in the unicellular intestinal bacteria Escherichia coli and Salmonella typhimurium.