The effect of sewage effluent on Grasmere (English Lake District) with particular reference to inorganic nitrogen transformations

SUMMARY. In the summer of 1971 the village of Grasmere was converted from septic tank to mains drainage with sewage treatment at an activated sludge plant. The effluent was discharged into the River Rothay, the main inflow of a nearby small lake (Grasmere). This paper describes some of the effects on the lake. The mean areal hypolimnetic oxygen deficit increased from 274 to 434 mg O₂ m⁻² day⁻¹ with an accompanying marked increase in the degree of deoxygenation in the hypolimnion. Plate counts of bacteria in the surface water increased for 2 years but this increase was not sustained. The mean summer soluble reactive phosphorus concentration did, however, increase significantly ( P = 0.05), but the same was not true of nitrate levels. This paper is particularly concerned with inorganic nitrogen transformations and analyses of the main inflow have shown that 50–98% of the ammonia and 10–40% of the nilrate entering in this river was derived from the sewage effluent. The concentrations in the main body of the lake were usually lower, possibly due to assimilation and denitrification in the shallower reaches of the lake. Seasonal changes in the inorganic nitrogen species in the hypolimnion showed three distinct phases of activity, ammonification, nitrification and denitrification. Nitrification accounted for approximately a quarter of the oxygen uptake in the hypolimnion.     

The Exudation from Excised Maize Roots Bathed in Sulphate Media

The fluid exudation fluxes of excised maize roots bathed ina variety of K₂SO₄ solutions have been measured, along withthe ionic concentrations and osmolalities of the exudates. Anapparent imbalance of inorganic ionic charge in the exudate,and a discrepancy in the total salt concentrations comparedwith the measured osmolalities, suggest the presence of significantamounts of organic anions in the exuded fluid. Thin-layer chromatographicmethods indicate these to be mainly amino-acids and organicacids of the Kreb's cycle. Linear regression analysis showsthat the exudation flux is satisfactorily described by a simpleosmotic process together with a constant non-osmotic water fluxof 0.43 µ1 cm^-2 h^-1. The osmotic permeability for theroot is found to be 0.18 x 10^-6 cm sec^-1 atm^-1. The exudationfrom sulphate media is contrasted with that from chloride media.     

Pollen-Derived Haploids of Nicotiana Knightiana, N. raimondii, and N. attenuata

Haploid plantlets were obtained in large numbers in three diploid,24-chromosome species of Nicotiana by culture of anthers ator just past the first pollen mitosis. The three species wereN. Knightiana, N. raimondii, and N. attentiata. Efficiency ofhaploid production varied from about 10 per cent in N. attenuatacultures to 30 and 38 per cent respectively in cultures of N.raimondii and N. Knightiana. H-medium without hormones and standardcultural conditions were used. N. Knightiana appeared to beespecially suitable for haploid studies on account of its highplantlet productivity, low chromosome number, and distinctivekaryotype.     

Ultrastructure of the Erythrocytic Stages of Plasmodium malariae1

This report describes the fine structure of the erythrocytic stages of Plasmodium malariae. Erythrocytic parasites from a naturally acquired human infection and an experimentally infected chimpanzee were morphologically indistinguishable and structurally similar to other primate malarias. New findings included observations of highly structured arrays of merozoite surface coat proteins in the cytoplasm of early schizonts and on the surface of budding merozoites and the presence of knobs in the membranes of Maurer's clefts. Morphological evidence is presented suggesting that proteins are transported between the erythrocyte surface and intracellular parasites via two routes: one associated with Maurer's clefts for transport of membrane-associated knob material and a second associated with caveolae in the host cell membrane for the import or export of host- or parasite-derived substances through the erythrocyte cytoplasm.     

Effects of artificial ultraviolet-B radiation on growth and fatty acid composition of duckweed (Lemna minor)

1. Duckweed (Lemna minor), collected either in summer or early fall was exposed under laboratory conditions to control (photosynthetically active and UV‐A radiation) or experimental (control plus UV‐B radiation) conditions. 2. Growth and survival were determined by counting the number of green, and brown/white fronds following 1–5 or 11 days of irradiation. Growth of duckweed was impaired by exposure to UV‐B radiation in the fall experiment but not in the summer. 3. Fatty acid compositions were analysed following 5 or 11 days of irradiation and a recovery period of 0, 5, 29 or 40 h. Concentrations of the major fatty acids, palmitic, linoleic (LA) and α‐linolenic (ALA) acids were similar in the summer and fall duckweed collections, but the summer samples had higher concentrations of the desaturation products of LA and ALA. 4. UV‐B exposure had small, but significant, and contrasting effects on duckweed fatty acid concentrations. In the summer experiment, duckweed exposed to UV‐B had slightly lower concentrations of major fatty acids than control duckweed, while the reverse was true in the fall experiments. 5. These minor effects of UV‐B on concentrations of LA and ALA would be unlikely to have a major impact on the supply of these essential fatty acids from duckweed to freshwater food webs.