Concentrations Of PbCl2 Research Articles

The effects of lead on algae

Lead inhibits respiration and photosynthesis in Phaeodactylum. In cells treated for 24 h with PbCl2 (10 mg 1−1), photosynthesis is completely suppressed, while respiration is reduced to 25%. A lower concentration, 1.0 mg 1−1, permits photosynthesis at 75% of the control rate, respiration being virtually unaffected. The vital activities of cells treated for 48 h or 72 h are progressively more inhibited: concentrations of PbCl2 as low as 0.1 mg 1−1 reduce photosynthesis and respiration by 25 to 50%.

Der Einfluß von Bleiionen auf Enzyme der Chlorophyllbiosynthese / Influence of Lead-ions on Enzymes of the Chlorophyll Biosynthesis

Abstract The influence of different concentrations of PbCl2 on the activity of several enzymes of the chlorophyll biosynthesis in isolated spinach chloroplasts was analyzed. The succinyl-CoA-synthetase was weakly inhibited; a concentration of 2 mᴍ PbCl2 reduced the enzyme activity for 30% only. The concentration of δ-aminoevulinic acid (ALA) after incubation of the chloroplast homogenate with the substrates for the succinyl-CoA-synthetase + ALA-synthetase (cf. Fig. 9) was increased by lower concentrations of PbCl2 (0 - 50 μm) and decreased by higher (>50 μm). This can be explained by a correspondent influence of PbCl2 on the activity of ALA-synthetase or (more probably) by a relative stronger inhibitory effect of PbCl2 on the ALA-metabolizing than on ALA-producing enzymes. δ-Aminoevulinic acid dehydratase is strongly inhibited at low concentrations of PbCl2, as it is in animals. The same is true for porphobilinogenase

The effects of lead on algae. I. Effects of Pb on viability and motility of 'Platymonas subcordiformis' (Chlorophyta: Volvocales).

The effects of lethal and sublethal concentrations of PbCl2 on reproduction , viability, and motility of a marine unicellular green flagellate alga, Platymonas subcordiformis, were studied under controlled laboratory conditions. The severity of the effects depended primarily upon the concentration of Pb++ and the duration of treatment. Log phase cells were more sensitive than stationary phase cells. Sublethal amounts of Pb (2.5 and 10 mg l−1 Pb++) tended to retard population growth by delaying cell division and daughter cell separation. A lethal amount of Pb (60 mg I−1 Pb+) caused inhibition of growth and cell death. Various intracellular abnormalities resulted from Pb treatment. The flagella were shed or altered in a variety of ways, depending on Pb concentration; motility was least affected by low Pb and completely impaired by high Pb. Normal wild-type cells appeared to be more sensitive to Pb than mechanically sheared (flagella-less) cells and cells of a non-flagellate mutant of Platymonas. Exposure of cells to Pb in non-growth conditions of dark and cold (2°C) had little negative effect.

Luminescence and electrical conductivity of KCl-PbCl2 crystals grown from aqueous solutions

Luminescence spectra of KCl-PbCl2 crystals grown from aqueous solutions are compared with those of KCl-PbCl2 crystals grown from a melt. It is found that at PbCl2 concentrations C > 3·10−3 mole % there appears in the luminescence spectrum of “solution-type” crystals a new band with a peak at the 365-nm wavelength, which has never been noted in the case of “melt-type” crystals. The appearance of this band is attributed to (PbCln)−(n−2) complexes entering the crystals when the latter are grown from solutions. The concentration characteristics of ion conductivity are analyzed here and seem to confirm the hypothesis of this complex formation.

Growth of Potassium Chloride Crystals from Aqueous Solutions. I. The Effect of Lead Chloride

Single crystals of potassium chloride were grown from aqueous solutions under carefully controlled conditions of supersaturation, agitation, and impurity lead chloride concentration. The growth rate of the (100) face was determined. It was found that PbCl2 concentrations as low as 10−8 moles PbCl2/mole KCl decreased the rate of growth, and the retardation increased markedly with increasing PbCl2 concentration. The growth process changed from a layer type to a dendritic form over a small supersaturation range. Mass transfer rates of both KCl and PbCl2 from the solution to the crystal face were estimated and conditions delineated where each may be the rate-controlling step. A mechanism is proposed to account for the formation of crystal clusters on the surface of KCl at slow stirring rates.