Oxygen

About: Oxygen is a research topic. Over the lifetime, 48149 publications have been published within this topic receiving 1113788 citations. The topic is also known as: O & Oxygen.

The effect of oxygen concentration on the decomposition of organic materials in soil

Abstract: 1. Techniques are described for relating the oxygen concentrations in the soil water on the surfaces of micro-organisms to their metabolizing activities. 2. Studies were made on the decomposition of organic materials in water-saturated crumbs (mean radius 1.55 × 10−1 cm) of a loam soil. 3. Respiration of water-saturated crumbs was not inhibited unless the oxygen concentration was less than about 10−6 M. Evidence was obtained that above a similar low oxygen concentration there was no inhibition of respiration in soils of widely different type. 4. Anaerobic decomposition of the soil organic matter was very slow. Anaerobic decomposition of casein digest was more rapid than that of any other material tested; the products were water soluble and included 83 µ-equivalents of volatile fatty acid per mg of α-amino-N decomposed. 5. Casein digest percolation of soil crumbs under air resulted in the formation of micro-organisms that respired at 70 per cent of their maximum rate when the oxygen concentration was about 2.7 × 10−6 M. 6. No products of anaerobic casein digest decomposition could be detected on percolating casein digest through soil crumbs when 80 per cent of the soil contained no oxygen and the maximum concentration in any part of the soil was about 3 × 10−5 M. 7. The kinetics of oxygen uptake consequent on the decomposition of casein digest and of other simple organic compounds in soil crumbs were similar and were only slightly affected by reduction of oxygen partial pressure in the atmosphere from 15 to 1.7 cm of mercury. 8. It is concluded that ‘change-over’ from aerobic to anaerobic metabolism of organic materials takes place in widely different soils at an oxygen concentration less than about 3 × 10−6 M.

Oxygen Evolved by Isolated Chloroplasts

Abstract: THE high affinity for oxygen possessed by muscle haemoglobin suggested its use as a very sensitive spectroscopic method for detecting and measuring small quantities of oxygen1. This method has now been applied to study the oxygen evolution of isolated chloroplasts exposed to light. While being much less sensitive than the bacterial methods which have been successfully applied in the past, the haemoglobin method (originally used by Hoppe-Seyler to demonstrate oxygen from green plants) has the advantage of giving the measure of oxygen. A solution of haemoglobin containing 0.45 × 104 gm. atoms of iron per litre, is equivalent to 1 c.mm. of oxygen per c.c.; the degree of saturation can be determined spectroscopically with an accuracy of 5 per cent.

Oxygen dynamics in the rhizosphere of Cymodocea rotundata

Abstract: The spatial distribution of oxygen and the dynamics of the oxic mlcrozone around roots of Cymodocea rotundata were studied using oxygen microelectrodes under constant light conditions and during light-dark transitions. Under daylight steady state conditions, oxygen was present at concentrations up to 75 % of air saturation at the root surface, and the oxic microzone around the roots was 80 pm thick. Steady state oxygen concentrations were reached within 1.5 h after light-dark shifts. Under darkness, free oxygen, at about 20% of air saturation, was still present on the root surface at steady state, but the thickness of the oxic microzone shrank to 50 pm. The oxygen present in the rhizosphere during darkness was supplied from the water column to roots via, primarily, gas-phase diffusion in leaves and rhizomes. The oxic microzone around roots comprised about 0.5% of the total volume of the seagrass rhlzosphere, and the root-mediated oxygen supply was estimated to be insignificant for the whole sediment oxygen budget contributing about 1 % of total oxygen consumption only. However, the continuous oxygen supply may ensure a persistent oxic environment for belowground tissues of C. rotundata and, hence, protect the plant from reduced phytotoxins.

Sensor Photoresponse of Thin‐Film Oxides of Zinc and Titanium to Oxygen Gas

Abstract: Response of steady-state photoconductivity to changes in oxygen partial pressure (10{sup {minus}3} to 1 atm) has been quantitatively studied in thin-film polycrystalline TiO{sub 2}:Nb and ZnO at 80--120 C. The magnitude of photoconductivity varied as a square root of illumination intensity regardless of oxygen pressure. Both materials showed fast response to oxygen, although in different pressure ranges. Zinc oxide was more sensitive to lower oxygen pressures while titanium dioxide worked better at pressures close to 1 atm.