Modelling the effect of super‐atmospheric oxygen and carbon dioxide concentrations on the respiration of fresh‐cut butterhead lettuce

This experiment was conducted to observe the effect of the composition of atmospheric gases on the respiration of fruits and vegetables. The average of repiration rate of eggplants, Japanese pears, spinach and cauliflower (under storage in modified atmosphere) were lower than that under storage in air. Especially, the respiration rate of the products stored in modified atmosphere conta fined 5% oxygen and 5% carbon dioxide was about half of that in air. (Experiment I.)It is clear that a decline in the respiration of these products in storge is brought about by a combination of super-normal carbon dioxide concentration and reduced oxygen concentration. However, the data in experiment I has not been elucidated which is the main fatter concerning the reduction in respiration.In order to test the precise contribution of each of these fatter, experiment II was conducted both tests on oxygen and carbon dioxide concentrations in atmospheric gases on the respiration of vegetables. Carbon dioxide test was carried out at the range of 0-20% and oxygen test was carried out at the range of 5-25%.In this experiment, the respiration rate of some vegetables could be controlled either by decrease of oxygen concentration or by increase of carbon dioxide concentration.It was found that there was three phases to control the respiration rate in practical CA-storage. Three phases were as follows: (1) decrease of oxygen concentration, (2) increase of carbon dioxide concentration and (3) both decrease of oxygen concentration and increase of carbon dioxide concentration. Vegetables showed pattern (1) were spinach, pea in pod, kidney bean, lettuce, bell peppers and eggplants. They were very sensitive to the oxygen content in atmospheric gases. Cauliflower belonged to pattern (2) which shows relatively sensitive carbon dioxide concentration. Other vegetables which are pattern (3) are strawberries, celery, tomatoes, welsh onion and garden asparagus. These vegetables were sensetive to carbon dioxide and oxygen concentration in the atmospheric gases. Thus, it was considered that the response of vegetables to special gases reducing the respiration was different from the kinds of vegetables.

Predictive modelling and validation of Pseudomonas fluorescens growth at superatmospheric oxygen and carbon dioxide concentrations

Estimated time change of dissolved oxygen and carbon dioxide concentrations in the interstitial water of red sea bream, Pagrus major, egg aggregation

The effect of oxygen (low and superatmospheric concentrations), carbon dioxide and temperature on the respiration rate of fresh-cut butterhead lettuce, was evaluated. The lettuce was stored in glass jars at three different temperatures (1°C, 5°C and 9°C). The jars were flushed with humidified gas mixtures. Three carbon dioxide levels (0, 10 and 20 kPa) were combined with 8 different levels of oxygen concentrations (0, 2, 5, 10, 20, 50, 70 and 100 kPa). Temperature, carbon dioxide and oxygen concentrations significantly influenced the respiration rate. A model based on Michaelis-Menten kinetics to describe the respiration rates was constructed. The influence of temperature was described using an Arrhenius equation, and carbon dioxide was considered as an uneompetitive inhibitor of the respiration. The inhibiting effect of superatmospheric oxygen concentrations was described by a non-competitive inhibition term.

Fresh fruit respiration information is essential optimizing food storage systems. Meanwhile, respiration is defined as the process of oxygen production and carbon dioxide release during storage in a closed respiratory chamber. Therefore, this study aims to design a low-budget computerized respiratory chamber for enhancing fruit packaging and storage system. Real-time fruit respiration can be measured by applying wireless gas sensors network. The respirometer consisted of 3,600 mL glass jar with a screw stainless lid, while the electrochemical and non-dispersive infrared sensors were mounted on the cover of the glass jar for collecting data on the oxygen, carbon dioxide, and temperature during mangoes’ respiration. Arduino USB port was used to record all measured parameters consisting of oxygen (%) and carbon dioxide concentrations (ppm, as well as temperature in the respiration chamber. Additionally, a controlled cooling chamber was applied to maintain the temperature during storage, while data communication was supported by Xbee S2C based on radio frequency. According to the respirometer real-time reading, there was a decrease in oxygen concentration caused by increasing carbon dioxide release with temperature. The low-budget respirometer was used to measure the respiration rate and record the data through a wireless sensor network system. The data plot shows that the respiration rate increased as the storage temperature and the respiratory quotient ranged from 0.32-0.44.

Carbon assimilation at low carbon dioxide levels was measured on three Oryza specics (O. sativa L. cv. Toyonishiki, O. officinalis Wall, and O. meyriana Baill.), Brassica napus L. cv. Michinokunatane and Triticum aestivum L. cv. Konosu No.25. Measurements were made at two different oxygen concentrations; 140% and 21% (atmospheric pressure). An improvement in measurement device was made for ensuring an accuracy of the meter readings. That is, a recorder with a modulator was used to enlarge the differences in the carbon dioxide concentration; two- and five-fold for carbon dioxide levels above and below carbon dioxidc compensation point (gamma), respectively. It seems that HEATH and ORCHARD (1968) and HOLMGREN and JARVIS (1967) Changed the carbon dioxide concentration at large intervals, resulting in 3 to 5 measurements below gamma. Such a few measurements would obscure the statistics of the carbon dioxide exchangc rate at low carbon dioxide levels. The changes of carbon dioxide concentration in this experiment, however, were made at intervals of about 2 or 4 ppm from 0 ppm to gamma, resulting in 7 to 14 mean values below it. As the characteristics of carbon dioxide absorption at low carbon dioxide levels, GABRIELSEN (1948) proposed the 'threshold hyPothesis' in which gamma was regarded as a threshold value below which no assimilaton occurred, while HEATH and 0RCHARD (1968) postulated the existence of a 'third process', in addition to ordinary (dark) respiration and assimilation, which could be expected to have a different balance between respiration and assimilation. They denied the adoptation of the threshold hypothesis. From the prescnt experiment in which the carbon dioxide exchange rates were traced by Changing the Carbon dioxide concentrations at very small intervals, hwever, it appeared that the rate of carbon dioxide uptake at low carbon dioxide levels and atmospheric oxygen pressure tended to decrease toward 1/2 gamma carbon dioxide level, and the carbon dioxide uptake seems to cease and only the carbon dioxide release secms to occur below it. In case of measurements at 14% oxygen concentration the situation was similar to those at 2l% oxygen concentration, but a considerable decrease of the value of gamma. Thus, the process of carbon dioxide uptake at low carbon dioxide levels seems to imply the threshold hypothesis and 1/2 gamma seems to be an approximation of the threshold value. The assimilation rate is estimated as the ratio of carbon dioxide concentration differences between ambient air and assimilation center to the sum of diffusion resistances.As an estimate of carbon dioxide levels in the assimilation center in this formula, GAASTRA (1959) proposed zero, while BIERHUIZEN and SLAYTER (1964) adopted the Practise of using gamma to estimate it. From the results mentioned above, we could propose to use 1/2 gamma as its primary approximation because the photosynthetic center would be exposed to this carbon dioxide level but not absorb it.

Carbon dioxide concentration is likely to increase by 2–2.5 fold by the end of 21st century from its current level of 400 ppm due to anthropogenic activities mediated climate change. As yam is an important food and nutrition security crop, it is of paramount importance to assess the effect of climate change on the physiological processes especially photosynthetic efficiency to identify the climate-smart varieties to meet the future food demand. The aim of this experiment was to assess the net photosynthetic rate, stomatal conductance, intercellular CO2, transpiration and physiological water use efficiency of seven yam varieties subjected to 400 ppm (ambient), 600, 800 and 1000 ppm (elevated carbon dioxide concentration). All the parameters were found significant at P<0.001. The mean photosynthetic rate increased significantly increased at 400–1000 ppm and no down-regulation was observed. Similar trend was observed in case of intercellular CO2 and physiological water use efficiency (WUEinstantaneous and WUEintrinsic). However, stomatal conductance increased significantly up to 800 and decreased at 1000 ppm. Contrasting results were recorded with regard to transpiration, which steadily decreased at ascending carbon dioxide concentrations. Further, photosynthesis rate had a significant (P<0.001) positive linear correlation with the elevated carbon dioxide (R2 = 0.783) and intercellular CO2 concentration (R2=0.763). White yam and greater yam were found to be responsive to elevated carbon dioxide as photosynthetic rate at 1000 ppm increased up to ∼68% in comparison to 400 ppm.

Studies of onion root respiration I. Velocity of oxygen consumption in different segments of root at different temperatures as a function of partial pressure of oxygen

STUDIES IN THE PHYSIOLOGY OF SPERMATOZOA

Comparative respiration and methane production rates in Nearctic termites

Beet armyworm, Spodoptera exigua (Hübner), larvae were placed on sugarbeet (Beta vulgaris L.) and pigweed (Amaranthus hybridus L.) plants in outdoor chambers in which the plants were growing at either the ambient (≈350 μl liter−1) or ambient plus 350 μl liter−1 (≈700 μl liter−1) carbon dioxide concentration. A series of experiments was performed to determine if larvae reduced plant growth differently at the two carbon dioxide concentrations in either species and if the insect growth or survival differed with carbon dioxide concentration. Leaf nitrogen, water, starch, and soluble carbohydrate contents were measured to assess carbon dioxide concentration effects on leaf quality. Insect feeding significantly reduced plant growth in sugarbeet plants at 350 μl liter−1 but not at 700 μl liter−1 nor in pigweed at either carbon dioxide concentration. Larval survival was greater on sugarbeet plants at the elevated carbon dioxide concentration. Increased survival occurred only if the insects were at the elevated carbon dioxide concentration and consumed leaf material grown at the elevated concentration. Leaf quality was only marginally affected by growth at elevated carbon dioxide concentration in these experiments. The results indicate that in designing experiments to predict effects of elevated atmospheric carbon dioxide concentrations on plant–insect interactions, both plants and insects should be exposed to the experimental carbon dioxide concentrations, as well as to as realistic environmental conditions as possible.

Predictive modelling and validation of Listeria innocua growth at superatmospheric oxygen and carbon dioxide concentrations

We present robust methods for online estimation of cell specific oxygen uptake and carbon dioxide production rates (q(O2) and q(CO2), respectively) during perfusion cultivation of mammalian cells. Perfusion system gas and liquid phase mass balance expressions for oxygen and carbon dioxide were used to estimate q(O2), q(CO2) and the respiratory quotient (RQ) for Chinese hamster ovary (CHO) cells in perfusion culture over 12 steady states with varying dissolved oxygen (DO), pH, and temperature set points. Under standard conditions (DO = 50%, pH = 6.8, T = 36.5°C), q(O2) and q(CO2) ranges were 5.14-5.77 and 5.31-6.36 pmol/cell day, respectively, resulting in RQ values of 0.98-1.14. Changes to DO had a slight reducing effect on respiration rates with q(O2) and q(CO2) values of 4.64 and 5.47, respectively, at DO = 20% and 4.57 and 5.12 at DO = 100%. Respiration rates were lower at low pH with q(O2) and q(CO2) values of 4.07 and 4.15 pmol/cell day at pH = 6.6 and 4.98 and 5.36 pmol/cell day at pH = 7. Temperature also impacted respiration rates with respective q(O2) and q(CO2) values of 3.97 and 4.02 pmol/cell day at 30.5°C and 5.53 and 6.25 pmol/cell day at 37.5°C. Despite these changes in q(O2) and q(CO2) values, the RQ values in this study ranged from 0.98 to 1.23 suggesting that RQ was close to unity. Real-time q(O2) and q(CO2) estimates obtained using the approach presented in this study provide additional quantitative information on cell physiology both during bioprocess development and commercial biotherapeutic manufacturing.

Previous work indicated that long-term exposure to ele- vated carbon dioxide levels can reduce hydraulic conduc- tance in some species, but the basis of the response was not determined. In this study, hydraulic conductance was measured at concentrations of both 350 and 700 cm 3 nT 3 carbon dioxide for plants grown at both concentrations, to determine the reversibility of the response. In Zea mays and Amaranthus hypochondriacus, exposure to the higher carbon dioxide concentration for several hours reduced whole-plant transpiration rate by 22-40%, without any consistent change in leaf water potential, indicating reversible reductions in hydraulic conductance at elevated carbon dioxide levels. Hydraulic conductance in these species grown at both carbon dioxide concentrations responded similarly to measurement concentration of carbon dioxide, indicating that the response was reversible. In Glycine max, which in earlier work had shown a long-term decrease in hydraulic conductance at elevated carbon dioxide levels, and in Abutilon theophrasti, no short-term changes in hydraulic conductance with measurement con- centration of carbon dioxide were found, despite lower transpiration rates at elevated carbon dioxide. In G. max and Medicago sativa, growth at high dew-point tempera- ture reduced transpiration rate and decreased hydraulic conductance. The results indicate that both reversible and irreversible decreases in hydraulic conductance can occur at elevated carbon dioxide concentrations, and that both could be responses to reduced transpiration rate, rather than to carbon dioxide concentration itself.

THE metabolic rate of small laboratory animals may be determined by either open or closed circuit respirometers. With the open circuit method, pure atmospheric air is inspired by the animal, then collected and analyzed for either oxygen or carbon dioxide concentration, or both. The composition of the inspired air must also either be known or determined. By difference, the rate of oxygen consumption or carbon dioxide production by the animal can be calculated for the period of observation. This method requires a good source of pure atmospheric air which is often difficult to obtain. A further drawback is the use of certain analytical procedures which are not necessary with the closed circuit system. The closed circuit arrangement has the advantage of permitting: 1) the use of pure oxygen, and 2) the direct measurement of the volume of oxygen consumed by the animal. There are many designs of apparatus of this type (Reineke and Turner, 1950).