An approach to quantifying various types of spontaneous activity

The output of an activity-measuring device is fed into low- and high-gain cumulative recorder channels which are reset to zero after different time periods. The records, inscribed at various paper speeds, are easily quantified. The tracing patterns can be identified with specific activities of undisturbed animals. The activities are monitored by means of closed-circuit television.     

Low-level irradiation and threshold shift in the visual receptor

Customary methods of stimulating and recording were used to examine threshold shifts of the single visual receptor in the lateral eye of Limulus in response to low-level x-irradiation. Marked visual sensitization was found and was most pronounced at the lowest dosage levels (1 to 25 r). Complete light adaptation apparently cancelled the effects of the irradiation.     

THE OCCURRENCE OF ETHYLENE IN ANAEROBIC SOIL

The production of ethylene and other hydrocarbon gases by soils under anaerobic conditions was measured by gas chromatography. Ethylene was the only hydrocarbon gas which occurred in physiologically significant concentrations; more than 20 ppm was found in several soils after 10 days at 20°C. These concentrations were considerably higher than those which were known to cause severe reductions in the extension of root axes of some plant species. Experiments with sterilized and unsterilized soil indicated that ethylene was produced by enzyme activity and not by chemical action. The gas was found in soil when the oxygen concentration fell below 2 per cent; total evolution was correlated with organic matter content, and was affected by drying and rewetting and by the growth of plant roots. The rate of production was increased by raising the temperature and by addition of glucose or peptone; high concentrations of nitrate depressed the rate, but sulphate and phosphate had little effect. It is concluded that ethylene may be a significant factor in causing injury to crop plants under waterlogged conditions and also in situations where anaerobic pockets occur within a mainly aerobic soil structure, provided that escape of the gas from the soil is impeded sufficiently to allow inhibitory concentrations to build up in the vicinity of plant roots.     

Gaseous diffusion through peat

Relative gas diffusivity (D/D₀) was measured in peat cores equilibrated to set moisture tensions between zero and - l0 kPa, using the radioactive gas ⁸⁵Kr. A relationship between relative diffusivity and the air filled porosity was obtained, which showed lower values of D/D₀ at air-filled porosities above about 0.13m³m⁻³, and higher values at porosities below about 0.10m³m⁻³ than some of those found in the literature for mineral soils. The likely effects of shrinkage behaviour on drying in the field, on the relationship between D/D₀ and air-filled porosity, are discussed.