DIFFERENCE TASTE THRESHOLDS FOR SUCROSE IN WATER AND IN ORANGE JUICE: AN INTERLABORATORY STUDY

Difference taste thresholds, expressed as jnd values or Weberratios, were determined for sucrose in water and in orange juiceat laboratories in Sweden, U.S.A., Poland and Switzerland usinga method of constant stimuli. The following total arithmeticmean values of all 172 individual jnd values were obtained:0.266 and 0.400% sucrose at 2 and 5% sucrose in water, respectively;0.977 and 1.19% sucrose at 1.5 and 3.75% sucrose in orange juice,respectively. The frequency distributions of the individualvalues were asymetrical and showed a large variation among subjects.The results of some additional experiments at 2 and 5% sucrosein orange juice, performed only by the Polish laboratory, arereported also. Significance analyses performed according to one parametricmethod (t-test), using pooled data of groups of subjects, andone non-parametric method (Mann-Whitney's U-test), using individualthreshold values, gave the same conclusion in practically allcases. The data indicated that females had slightly lower average discriminationthresholds than males. There was a significant degree of correlationbetween subjects' discriminatory ability at different concentrationsof sucrose in each of the two media. Few significant differences between the laboratories were foundfor sucrose in water, whereas for sucrose in orange juice thefollowing rank order, from lowest to highest average jnd value,among the laboratories was obtained for both concentrationstested: Poland < U.S.A. < Sweden = Switzerland. Some speculationswere advanced as partial explanation for the differences amongthe laboratories. ^*Formerly Johansson     

Bioelectric Control of Regeneration in Tubularia

The theory of differentiation during regeneration by polarizedspecific repression in the bioelectric field as worked out inTubularia is reviewed and brought up to date. Similarities betweenthe studies with Tubularia and those on a variety of other organismsare discussed.     

Physical Responses of Yeast Cells to Osmotic Shock

Shock exposure of the osmophilic yeasts Saccharomyces rouxii, Torulopsis globosa and T. apicola to solutions of sucrose and polyethylene glycol of MW 200 (PEG 200) at water activity ( a_w ) values between 0.88 and 0.98 caused gradual changes in cell volumes in the test solutions, though cell volumes were consistently lower in PEG 200. Non-osmophilic yeasts, Sacch. cerevisiae , bakers'yeast and Schizosaccaromyces pombé showed responses similar to the osmophiles in sucrose solutions only, as cells in PEG 200 apparently equilibrated with external osmotic pressures by uptake of solute. Optical densities of cell suspensions supported the findings on cell volumes. Viability tests at the highest and lowest solute concentrations indicated that all test organisms withstood the osmotic shock over the test period. As the theoretical relationship between a_w and osmotic pressure breaks down in concentrated solutions, it is considered that the water relations of yeasts should not be considered exclusively in terms of a_w , but also in conjunction with osmotic pressure and solute uptake.     

Phytogeographical and ecological aspects of Lobarion communities in Europe

ROSE, F., 1988. Phytogeographical and ecological aspects of Lobarion communities in Europe. The Lobarion communities in Europe are reviewed on the basis of field surveys by the author from south-west Norway to the Pyrenees, Tuscany and Austria. Lobarion communities are still widespread in most montane forests, but in the lowlands are now largely restricted to the Atlantic coastal zone, evidently through forest management practices and air pollution. Evidence for the decline is discussed and causes are reviewed. The major species occurring in these communities in different regions of Europe are tabulated and this reveals interesting geographical patterns. The alliance is appropriately divided into three associations, one being newly proposed here for southern European communities with species drawn from the Xanthorion.