Pigment composition in Norway spruce needles suffering from different types of nutrient deficiency

 Concentrations of pigments in needles of yellowish Norway spruce [Picea abies (L.) Karst] trees suffering from either N, Mg or K deficiency in field sites in southeast Norway are reported. The yellowish trees had a considerably lower (roughly 50%) pigment concentration, as well as a lower chlorophyll/carotenoid ratio, compared to green trees within the same sites. Yellowing was interpreted as a general bleaching of colour, as well as a slight turn from the green (chlorophylls) towards yellow (lutein). Concentrations of pigments were highly intercorrelated. N deficiency was especially associated with low α-carotene concentrations. This was interpreted as α-carotene being the most sensitive pigment to stress. However, this pigment might be specifically sensitive to N deficiency. Carbohydrate concentrations were slightly higher in yellowish trees. Received: 5 June 1997 / Accepted: 29 August 1997     

Chemotaxis or migration inhibition of rabbit peritoneal polymorphonuclear leukocytes caused by chemoattractants at various concentrations

Purified lipopolysaccharide (LPS) from Veillonella incubated in normal rabbit serum was tested for chemotactic activity on rabbit polymorphonuclear leukocytes (PMNs) in modified Boyden chambers. In doses above those giving optimal response (over-optimal dose), a decrease of the PMN migration activity was found. This decrease also correlated well with an increase in the migration inhibition of the PMNs as demonstrated with the capillary tube assay. The PMN chemotactic factor isolated from LPS-induced inflammatory exudate (LPS-CF) in rabbits, produced both a decrease in chemotactic response and a migration inhibition of PMNs in over-optimal doses. This inhibitory effect was not due to cytotoxicity, proved by the trypan blue exclusion test. Also, a reduced locomotion of PMNs first preincubated with chemoattractants and then reactivated, was shown when the same PMNs were restimulated to migration using the same chemoattractants. This was interpreted as a deactivation of the cells. A cross-deactivation was demonstrated between LPS-CF and casein. The results from the experiments reported show that the Boyden chamber may be used to disciminate directional chemotaxis and migration inhibition. It may also be concluded from the study that the reduced migration activity of PMNs at over-optimal doses of chemoattractants is not due to cytotoxicity, but most probably is caused by a deactivation of the cells.     

Estimation of canopy density and irradiance in 20- to 40-year-old birch stands (Betula pubescens Ehrh. andBetula pendula Roth)

Three different experiments in birch (Betula pubescens Ehrh. andBetula pendula Roth) stands were conducted during summer 1991: an evaluation of the accuracy of the vertical tube method measuring crown free projection (CFP) in four birch stands; a study of relative irradiance (RI; photosynthetically active radiation, PAR), in birch stands differing in stem density and basal area; and an estimation of the CFP in different types of birch stands and the correlation between RI and CFP. The results indicate that the number of observation points well distributed over an area of 0.1 ha can vary between 50 and 200 to achieve sufficient accuracy. There were no significant differences in the CFP estimates made on the same plot by different observers including an untrained observer. CFP was related to basal area, stem number and diameter sum in a non-linear regression, CFP = A^*e^-BX. The correlations between RI and basal area, density and diameter sum, respectively, were 0.54, 0.57 and 0.67 for PAR. The coefficients of determination for RI (PAR) and CFP were high (0.86).     

Genetic mapping and cloning of the gene (trmC) responsible for the synthesis of tRNA (mnm5s2U)methyltransferase in Escherichia coli K12

Summary The trmC gene, responsible for the formation of 5-methylaminomethyl-2-thiouridine (mnm⁵s²U) from 2-thiouridine, present in the first position in the anticodon of some tRNAs, has been located at 50.5 min on the Escherichia coli K12 chromosome. Results from transductional mapping suggest that the trmC gene is located counter-clockwise of aroC. A ColE1 hybrid plasmid carrying the aroC ⁺, trmC ⁺ and hisT ⁺ genes was isolated, and the gene order was established, by subcloning, to be hisT-trmC-aroC. The trmC gene is located 1.9 kb from the aroC gene. Two mutations (trmC1 and trmC2) were shown to be recessive, suggesting that the trmC gene is the structural gene for the tRNA-(mnm⁵s²U)methyltransferase.