Internal Oxygen Concentration Research Articles

Permeance to oxygen of detached Capsicum annuum fruit

The internal oxygen concentration and rate of oxygen consumption of detached capsicum fruits (Capsicum annuum L.) were monitored over several days. From this their overall permeance to oxygen was calculated. When wax was applied to the pedicel and its scar, permeance was reduced by 80–90%, indicating that most gas exchange occurred through this area. Readings from O2 sensors attached to the skins of the fruits were compared to those from O2 sensors inserted into the fruit cavity. These indicated that the cuticle was the major barrier to gas diffusion and that there was a concentration gradient through the capsicum flesh. Permeance of the cuticle was found to be about 0.64 x 10–4 mol O2/Pa.m2.s, while permeance to CO2 was 2–3 times higher. This suggests that the cuticle is composed of a coherent film. The low rate of gas diffusion through capsicum cuticle may allow recycling of respired CO2 by photosynthesis in the flesh before harvest.

Effects of Sucrose Palmitic Acid Ester Coating on the Internal Gas Concentrations of Cavendish Bananas in Relation to the Ripening, Respiration and Ethylene Production.

The effects of a 2% sucrose palmitic acid ester coating were studied on the internal oxygen, carbon dioxide and ethylene concentrations of banana fruits in relation to ripening, respiration and ethylene production during storage at 20°C after treatment with 100 ppm ethylene for 12 h. The 2% sucrose palmitic acid ester coating on the bananas covered the stomatal aperture, suppressed initial respiration and decreased the rate of ethylene production which ultimately retarded degreening and significantly delayed (P<0.01) ripening. The internal oxygen concentration of the bananas was significantly (P<0.05) reduced by the coating treatment without elevation of the internal carbon dioxide level. Low internal oxygen concentration significantly reduced (P<0.01) the rate of ethylene production of the coated bananas during 9 days in storage. These observations indicated that coating with the sucrose palmitic acid ester modified the internal atmosphere of banana fruits and suppressed initial respiration in a manner analogous to modified atmosphere storage.

Oxygen and pressure changes measured in situ during flooding in roots of the Grey Mangrove Avicennia marina (Forssk.) Vierh.

Manometers and oxygen electrodes were attached to the root system of mangroves grown in pots flooded to soil level. Measurements of internal pressure and oxygen concentration were made at the tip and middle of cable roots and on a pneumatophore, in artificial tidal conditions in a constant temperature growth-room. At the end of a period of ‘low tide’ there was a substantial oxygen gradient within the root system, from 6.41 ± 0.26 mol m −3 at the middle of the cable root to 4.81 ± 0.37 mol m −3 at the cable root tip (means and standard errors, n = 8). All oxygen concentrations fell during ‘high tide’ when the whole plant except the shoot was submerged, and the internal gradients gradually diminished, until by the end of a 6-h flooding the concentration throughout was in the range 4.59 ± 0.37 mol m −3 to 2.82 ± 0.41 mol m −3. Concentrations and gradients recovered over a few hours after unflooding. The oxygen concentrations measured in the roots fell among those previously published. Pressure measurements within the root system showed pressures similar to atmospheric or slightly positive (with respect to atmospheric) throughout the root system at ‘low tide’, a rapid decline in pressure reaching −1.0 to −1.7 kPa after flooding, with a slow partial recovery to −0.8 to −0.4 kPa when flooding lasted much longer than normal high tide, and finally a rapid return to atmospheric pressure on unflooding. We suggest that the above-atmospheric pressure at ‘low tide’ is consistent with the possibility of thermo-osmotic pressurisation, and further tracer experiments are needed to test whether this would result in significant gas exchange by mass flow. The low pressure during ‘high tide’ is likely to result from removal of respiratory carbon dioxide from the gas space: it would be likely to result in an influx of air through the exposed shoot, and a brief rapid influx through the pneumatophores on unflooding.

Effects of Carbohydrate on the Internal Oxygen Concentration, Oxygen Uptake, and Nitrogenase Activity in Detached Pea Nodules

The interaction between carbon substrates and O(2) and their effects on nitrogenase activity (C(2)H(2)) were examined in detached nodules of pea (Pisum sativum L. cv "Sparkle"). The internal O(2) concentration was estimated from the fractional oxygenation of leghemoglobin measured by reflectance spectroscopy. Lowering the endogenous carbohydrate content of nodules by excising the shoots 16 hours before nodule harvest or by incubating detached nodules at 100 kPa O(2) for 2 hours resulted in a 2- to 10-fold increase in internal O(2), and a decline in nitrogenase activity. Conversely, when detached nodules were supplied with 100 millimolar succinate, the internal O(2) was lowered. Nitrogenase activity was stimulated by succinate but only at high external O(2). Oxygen uptake increased linearly with external O(2) but was affected only slightly by the carbon treatments. The apparent diffusion resistance in the nodule cortex was similar in all of the treatments. Carbon substrates can thus affect nitrogenase activity indirectly by affecting the O(2) concentration within detached nodules.

Diffusion of Oxygen in Relation to Structure and Function in Legume Root Nodules

Although substantial rates of oxidative phosphorylation by bacteroids of Rhizobium are required to support sustained N2 fixation in legume nodules, the enzyme nitrogenase is extremely sensitive to oxygen. This apparent paradox indicates that nodules must exercise effective control over internal oxygen concentration. Structural features including lenticel development, the thickness and arrangement of cells and air spaces in the inner and outer cortex, the presence or completeness of the common endodermis as well as the distribution of infected cells, uninfected cells and air spaces in the nodule medulla are important to gaseous ventilation of the organ. Among these, the organisation of cells and water / gas- containing extracellular voids in the inner cortex bounding the infected medulla zone are critical components to overall diffusive resistance. These elements also appear to provide the means for the oper- ation of a reversible variable diffusion barrier to control gas movement. Inhibition of nodule functioning by a widely diverse range of factors, e. g. restricted H2O or photosynthate supply, exposure to acetylene or combined N, appears to be mediated through increased diffusion resistance.

Die Überflutungstoleranz der Teichbinse (Schoenoplectus lacustris (L.) Palla): III. Beziehungen zwischen der Sauerstoffversorgung und der „Adenylate Energy Charge“ der Rhizome in Abhängigkeit von der Sauerstoffkonzentration in der Umgebung

Stalked rhizomes of the bulrush ( Schoenoplectus lacustris (L.) P alla ) contain an oxygen gradient from the shoot to the rhizome. The internal oxygen concentration does not fall below 10 %, even if the environment of the rhizome is oxygen free. The oxygen provision is used up 1 h after cutting the stalk. Plants in their natural habitat behave in the same way. The difference in oxygen uptake between stalked rhizomes and rhizomes without stalks demonstrates an apparent oxygen transport. The calculation of the true oxygen transport shows, that more than 70 % of the oxygen used is delivered from the shoot. Shortening of the stalk improves the oxygen supply of the rhizomes The good oxygen supply is also demonstrated by the high values of the energy charge (>0.8). Unstalked rhizomes have intermediary valus (0.5—0.7). From these results we conclude that efficient oxygen transport is the main strategy in relation to the flooding tolerance of this plant

Radial Oxygen Loss from Roots: The Theoretical Basis for the Manipulation of Flux Data Obtained by the Cylindrical Platinum Electrode Technique

AbstractA résumé is given of the cylindrical platinum electrode technique for measuring the rate of oxygen release from the submerged roots of intact plants.Methods are then described for manipulating the oxygen flux data to quantify the following root characteristics: total effective internal diffusional resistance, non‐metabolic (pore‐space) resistance, internal apical oxygen concentration, effective diffusion coefficient of internal transport and fractional porosity, and the respiratory contribution to internal transport. The diffusional resistance of the root wall is discussed and the method formerly suggested for converting low temperature flux data to the appropriate room temperature values (Armstrong 1971) is revised. Finally, suggestions are made for overcoming the difficulties encountered in using flux data for comparative work if the roots differ in their apical radii.

Effects of Curing on the Internal Oxygen Concentration of Peanuts

Over the years peanut curing practices have changed from the stackpole method to bulk curing in conjection with window harvesting.Butt and Kummer(1951) and Teter(1957) indicated that use of curing air heated in excess of 35 C adversely affects peanut flavor.

Evaluation of Wax Coatings for Improving Sugarbeet Storage1

The effect of paraffin and a commercial wax coating on the respiration rate and weight loss of large and small sugarbeet (Beta vulgaris L.) roots was determined.Wax coatings on sugarbeets were most beneficial in reducing respiration rates under conditions where rates were high and gaseous diffusion became a dominant factor in regulating respiration rates. The respiration rate of the beet root was primarily a function of the internal oxygen concentration for a given size of beet.The internal oxygen concentration reflects the resistance of the beet to gaseous diffusion and surface area. The sensitivity of the internal oxygen concentration to increased diffusion resistance makes surface coating appear to be a practical method of lowering internal 02 and thus reducing respiration losses.The observation that wax coatings reduce desiccation and respiration rates suggests that spraying surface beets with a wax coating and then covering them with straw may prevent desiccation on the surface of commercial storage piles and thus reduce sucrose losses.

The use of a thermal model of ignition to explain aspects of flameproof enclosure

In an earlier paper (Combustion and Flame19, 187 (1972)) Phillips described the ignition process that occurs when a transient of hot inert gas is ejected into a flammable atmosphere through the equatorial flange gap of an 8-litre sphere for the determination of the Maximum Experimental Safe Gap (MESG) for flameproof enclosure. The analysis of the mechanism of ignition is now extended to take into account changes in flange breadth, vessel volume, internal ignition position, oxygen concentration, humidity, pressure, and ambient temperature. The results of the calculations agree with experimental data.

Factors Affecting Internal Oxygen and Carbon Dioxide Concentration of Citrus Fruits

Abstract The objectives of this study were to show the variations of internal gases of Orlando tangelos, Temple oranges, and Marsh grapefruit before storage and how waxing, storage temperatures, and various external O2 and CO2 concentrations affected internal gas composition. These tests were part of an overall project to determine the best controlled atmosphere (CA) conditions for storage of citrus fruits. Since internal O2 and CO2 concentrations may affect fruit quality (1), one concern in the addition of CO2 to the external atmosphere during CA storage was that the concentration of this component would continue to build up internally. Eaks and Ludi (1) have shown that the internal atmospheres of citrus fruits are affected by temperature, washing, and waxing. Vines and Oberbacher (4) found that certain packinghouse treatments increased CO2 concentrations within citrus fruits.

Factors Affecting Internal Oxygen and Carbon Dioxide Concentration of Citrus Fruits

Abstract The objectives of this study were to show the variations of internal gases of Orlando tangelos, Temple oranges, and Marsh grapefruit before storage and how waxing, storage temperatures, and various external O2 and CO2 concentrations affected internal gas composition. These tests were part of an overall project to determine the best controlled atmosphere (CA) conditions for storage of citrus fruits. Since internal O2 and CO2 concentrations may affect fruit quality (1), one concern in the addition of CO2 to the external atmosphere during CA storage was that the concentration of this component would continue to build up internally. Eaks and Ludi (1) have shown that the internal atmospheres of citrus fruits are affected by temperature, washing, and waxing. Vines and Oberbacher (4) found that certain packinghouse treatments increased CO2 concentrations within citrus fruits.

Respiration &amp; Internal Atmosphere of Avocado Fruit

and the composition of the internal atmosphere has been studied in several fruits. In the case of the banana (Musa sapientum) and the papaya (Carica papaya), Wardlaw and Leonard (24, 25) observed the coincidence of the onset of the climacteric rise with the peak in oxygen concentration inside these fruits. With the respiratory rise the oxygen level dropped, reaching very low values of 1 % at late stages of senescence. Impressed with the marked changes in the gaseous composition, they suggested that the internal oxygen concentration is the controlling mechanism of the climacteric pattern. Trout et al. (22) reported that in mature apples oxygen deficiency depressed respiration and retarded ripening. Observations on the epidermal layers as the tissue that offers major resistance to gaseous diffusion were made by Trout et al. (22) for the apple and by Clendenning (7) for the tomato. Biale (4) included in his review a brief account of the studies dealing with the internal atmospheres of fruits. The avocado fruit is distinguished from other fruits by its low fermentative capacity, shown by depression of CO2 evolution and ripening under anaerobic conditions (3). This study was undertaken, therefore, with the purpose of finding an explanation for the physiological behavior of the avocado in terms of changes in the composition of the internal atmosphere.

Variation in the haemoglobin content of Daphnia.

It is known that the concentration of haemoglobin inDaphniavaries inversely with the amount of oxygen dissolved in the water in which the animal lives, and that this variation is influenced by temperature and certain dietary factors. The individual variation in haemoglobin concentration found in populations ofDaphniaspecies has now been analyzed. One reason for individual variation was already known, namely, the stage of the instar in which an individual happens to be, for at the end of an instar haemoglobin passes from the blood into the eggs before they are laid. The haemoglobin concentration in the blood is gradually restored during the following instar. It is now shown that, with a large enough number of eggs, the passage of haemoglobin into the eggs is sufficient to account for the observed rate of loss of haemoglobin from the blood of redDaphniawhen in well aerated water. The concentration of haemoglobin is found to be higher in immature than in mature females, and males have a higher concentration than females under the same conditions. Fluctuations in haemoglobin and total haem concentrations in a population ofD. magnahave been followed for a period of three months.Daphniadoes not appear to store haem. The amount of haem passed into parthenogenetic eggs varies with the number of eggs per brood. Species ofDaphniadiffer in their ability to synthesize haemoglobin. It was found that when two pairs of pond-dwelling species are compared, the smaller species in each pair produces a higher concentration of haemoglobin than the larger one at the same low oxygen concentration. Racial and clonal differences in ability to synthesize haemoglobin were found within a single species ofDaphnia. It is concluded that much of the individual variation in haemoglobin concentration at any one oxygen concentration can be explained by individual differences in metabolic rate, which in turn can be related to the age, size and sex of the individual. A high metabolic rate lowers the internal oxygen concentration and so intensifies the stimulus to synthesize haemoglobin.

Effects of skin coatings on the behaviour of apples in storage. I. Physiological and general investigations.

The effects of skin coatings on the physiological behaviour of apples have been investigated and a mechanism for the effects has been suggested. Using mainly the variety Granny Smith, the composition of the internal atmosphere, respiration rate, and other changes associated with ripening have been studied in both uncoated and coated apples. The effects were found to depend greatly on temperature, thickness and type of coating, and variety and condition of the fruits. Coating increased the resistance of the skin to gaseous diffusion and thus greatly reduced the internal oxygen concentration, increased the internal carbon dioxide concentration, reduced the respiration rate, and retarded ripening changes by varying degrees. The most spectacular effect on ripening was a marked retardation of normal yellowing of the skin, which is mainly controlled by internal oxygen supply.