Constant Respiration Research Articles

Computational investigation of flow characteristics and particle deposition patterns in a realistic human airway model under different breathing conditions

Airborne particle pollution causes a range of respiratory and cardiovascular disorders by entering the human respiratory system through the breathing process. The administration of pharmaceutical particles by inhalation is another effective way to treat pulmonary illnesses. Studying particle deposition in the respiratory system during human breathing is crucial to maintaining human health. This necessity served as the impetus for this work, which aims to investigate how the airflow and particles' deposition are influenced by constant inhalation and circulatory breathing, particle diameter, and changes in airflow rate. The focus of this paper is to compare the particle deposition results of circulatory respiration with constant respiration. Based on computed tomography (CT) scan pictures, a precise human airway model from the mouth cavity to the fifth-generation bronchi was created. Flow fields and particle deposition inside the respiratory tract were examined at varied breathing rates (30, 60, and 90 L/min of constant and circulatory breathing) and varying haled particle sizes (5 and 10 µm). The results showed that the oropharyngeal area is often where the majority of particles are deposited. The particle distribution fraction is more significant in the bronchial area than the oropharyngeal region due to lower inhalation velocities and smaller particle sizes. For particles with a diameter of 5 µm, constant respiration and circulatory respiration have virtually identical particle distribution fractions in each region. For particles with a diameter of 10 µm, the particle distribution fraction for circulatory respiration is slightly higher than for constant respiration in the bronchial region as the flow rate increases. For both constant and circulatory respiration, particles are deposited more in the right lung and less in the left. These results contribute to further research on respiratory diseases caused by inhaled particles and guide inhalation therapy for better treatment outcomes.

Blood and cerebrospinal fluid flow oscillations measured with real-time phase-contrast MRI: breathing mode matters

BackgroundCervical blood and cerebrospinal fluid (CSF) flow rates can be quantified with Phase-contrast (PC) MRI, which is routinely used for clinical studies. Previous MRI studies showed that venous and CSF flow alterations are linked to various pathological conditions. Since it is well known that, besides the heart beating, the thoracic pump influences the blood and CSF dynamics, we studied the effect of different respiration modes on blood and CSF flow rates using a real-time (RT)-PC prototype.MethodsThirty healthy volunteers were examined with a 3 T scanner. A RT-PC sequence was acquired at the first cervical level to quantify the flow rates of internal carotid arteries, internal jugular veins (IJVs) and CSF. Each RT-PC acquisition was repeated three times, while the subjects were asked to breathe in three different ways for 60 s each: freely (F), with a constant rate (PN) and with deep and constant respiration rate (PD). The average flow rates were computed, they were removed from the respective signals and integrated in the inspiratory and expiratory phases (differential volumes). Finally, the power spectral density was computed for each detrended flow rate. High- and very-high frequency peaks were identified on the spectra while their frequencies were compared to the respiratory and cardiac frequencies estimated using a thoracic belt and a pulse oximeter. The area under the spectra was computed in four 0.5 Hz-wide ranges, centered on the high-frequency peak, on very-high frequency peak and its 2nd and 3rd harmonics, and then they were normalized by the flow rate variance. The effect of breathing patterns on average flow rates, on systolic and diastolic peaks, and on the normalized power was tested. Finally, the differential volumes of inspiration were compared to those of expiration.ResultsThe frequencies of the high- and very-high spectral peaks corresponded to the respiratory and cardiac frequencies. The average flow rate progressively decreased from F to PN to PD breathing, and the cardiac modulations were less predominant especially for the IJVs. The respiratory modulation increased with PD breathing. The average volumes displaced in the inspiratory phases were not significantly different from those of the expiratory one.ConclusionsThe spectral analyses demonstrated higher respiratory modulations in PD compared to free breathing, even prevailing the cardiac modulation in the IJVs, showing an increment of the thoracic pump affecting the flow rate shape.

Respiration Rate Estimation Based on Independent Component Analysis of Accelerometer Data: Pilot Single-Arm Intervention Study.

BackgroundAs the mobile environment has developed recently, there have been studies on continuous respiration monitoring. However, it is not easy for general users to access the sensors typically used to measure respiration. There is also random noise caused by various environmental variables when respiration is measured using noncontact methods in a mobile environment.ObjectiveIn this study, we aimed to estimate the respiration rate using an accelerometer sensor in a smartphone.MethodsFirst, data were acquired from an accelerometer sensor by a smartphone, which can easily be accessed by the general public. Second, an independent component was extracted to calibrate the three-axis accelerometer. Lastly, the respiration rate was estimated using quefrency selection reflecting the harmonic component because respiration has regular patterns.ResultsFrom April 2018, we enrolled 30 male participants. When the independent component and quefrency selection were used to estimate the respiration rate, the correlation with respiration acquired from a chest belt was 0.7. The statistical results of the Wilcoxon signed-rank test were used to determine whether the differences in the respiration counts acquired from the chest belt and from the accelerometer sensor were significant. The P value of the difference in the respiration counts acquired from the two sensors was .27, which was not significant. This indicates that the number of respiration counts measured using the accelerometer sensor was not different from that measured using the chest belt. The Bland-Altman results indicated that the mean difference was 0.43, with less than one breath per minute, and that the respiration rate was at the 95% limits of agreement.ConclusionsThere was no relevant difference in the respiration rate measured using a chest belt and that measured using an accelerometer sensor. The accelerometer sensor approach could solve the problems related to the inconvenience of chest belt attachment and the settings. It could be used to detect sleep apnea through constant respiration rate estimation in an internet-of-things environment.

GmGPDH12, a mitochondrial FAD-GPDH from soybean, increases salt and osmotic stress resistance by modulating redox state and respiration

In plants, glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the interconversion of glycerol-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP) coupled to the reduction/oxidation of the nicotinamide adenine dinucleotide (NADH) pool, and plays a central role in glycerolipid metabolism and stress response. Previous studies have focused mainly on the NAD+-dependent GPDH isoforms, neglecting the role of flavin adenine dinucleotide (FAD)-dependent GPDHs. We isolated and characterized three mitochondrial-targeted FAD-GPDHs in soybean, of which one isoform (GmGPDH12) showed a significant transcriptional response to NaCl and mannitol treatments, suggesting the existence of a major FAD-GPDH isoform acting in soybean responses to salt and osmotic stress. An enzyme kinetic assay showed that the purified GmGPDH12 protein possessed the capacity to oxidize G3P to DHAP in the presence of FAD. Overexpression and RNA interference of GmGPDH12 in soybean hairy roots resulted in elevated tolerance and sensitivity to salt and osmotic stress, respectively. G3P contents were significantly lower in GmGPDH12-overexpressing hair roots and higher in knockdown hair roots, indicating that GmGPDH12 was essential for G3P catabolism. A significant perturbation in redox status of NADH, ascorbic acid (ASA) and glutathione (GSH) pools was observed in GmGPDH12-knockdown plants under stress conditions. The impaired redox balance was manifested by higher reactive oxygen species generation and consequent cell damage or death; however, overexpressing plants showed the opposite results for these traits. GmGPDH12 overexpression contributed to maintaining constant respiration rates under salt or osmotic stress by regulating mRNA levels of key mitochondrial respiratory enzymes. This study provides new evidence for the roles of mitochondria-localized GmGPDH12 in conferring resistance to salt or osmotic stress by maintaining cellular redox homeostasis, protecting cells and respiration from oxidative injury.

Oxygen dynamics and evaluation of the single-station diel oxygen model across contrasting geologies

Abstract. In aquatic ecosystems, the single-station, single-stage R diel oxygen model assumes constant ecosystem respiration and aeration rate (notwithstanding temperature effects) over the course of a single night. The validity of this model was assessed for four small streams representing two geologies (Chalk and Greensand) over a 1-year period, by examining the behaviour of the nighttime dissolved oxygen (DO) saturation deficit for each night at points where change in DO is zero. The resulting value was then compared with the corresponding ratio (the regression quotient) obtained from nighttime regression analysis (Hornberger and Kelly, 1975). If model assumptions are correct, then these two values should be equal; where they diverge therefore gives a method of assessing the suitability of the model structure. For two streams (one Chalk and one Greensand), the regression quotient persistently underestimated the observed DO deficit. These two streams showed similar timing patterns of oxygen dynamics with the point of minimum DO occurring relatively quickly after sunset in spring and early summer, although the two Chalk streams were more similar to one another in terms of DO magnitudes. Comparisons between different streams using the single-station model with constant R and k on the presumption that it is equally appropriate in all cases may lead to misleading conclusions.

Non-contact monitoring of human respiration using infrared thermography and machine learning

The respiration rate (RR) is an important indicator of human health condition. The well-established RR monitoring techniques are mostly contact processes, which have many limitations, especially for premature neonates with fragile skin. The present study reports application of Infrared Thermography for continuous and reliable monitoring of the RR, through a non-invasive and non-contact approach. Here, the temperature modulation across the nostrils during the respiration process is monitored using a thermal camera. The signal to noise ratio (SNR) of the obtained breathing waveform, is improved by subjecting it to suitable filtering techniques. The performance of the filters is compared using various parameters such as SNR, Mean square error, magnitude response, and group delay. Further, a computer vision algorithm “Ensemble of regression trees” is implemented to track the nostrils (region of interest) in the presence of significant head movement as well as object occlusion, in an automated manner. A novel “Breath detection algorithm” (BDA) is also developed to differentiate normal and abnormal breaths by predefined thresholds and obtain the breaths per minute, without any manual intervention. The robustness of the proposed algorithm is tested by implementing it on 80 breathing waveforms under various conditions, such as constant respiration, slow and fast breathing, different focal conditions, and presence and absence of air conditioner and fan. The performance of the algorithm is determined by computing its Precision, Sensitivity, Spurious cycle rate, and Missed cycle rate values, which are 98.76%, 99.07%, 0.92%, and 1.23% respectively. The parameters obtained from the proposed BDA are further fed to a 10-fold cross-validation k-Nearest Neighbour (k-NN) classifier, which uses multi-class classification to decide whether the human volunteer has normal or abnormal respiration in general, or is suffering from Bradypnea (slow breathing) or Tachypnea (fast breathing) in particular. The robustness and performance of the k-NN classifier is determined by computing its Training accuracy, Validation accuracy, and Testing accuracy, obtained as 98.59%, 99.5% and 98%, respectively. Other performance metrics such as Sensitivity, Specificity, Precision, and F-measure values are calculated as well, for each class separately. Finally, a standard deviation value of 0.0102 is obtained from the outputs of the 10-fold cross-validation method. Further, the pattern between the data points fed to the k-NN classifier is observed using the t-Stochastic Neighbour Embedding algorithm.

Measurement of gas-exchange rate in streams by the oxygen–carbon method

The gas-exchange rate between streams and the atmosphere is needed to measure in-stream ecological processes and C processing in rivers and streams. Current methods include empirical relationships to hydraulics, direct injection of a tracer gas, and modeling based on O2 or C diel curves. All existing methods have strengths and drawbacks and most are limited to point measurements or are unable to measure diel variation in exchange rate. Researchers continue to search for better techniques, particularly for steep streams with high rates of gas exchange and low primary productivity. We present the O2−C (OC) method for calculating gas-exchange rates via simultaneous measurement of O2 and dissolved inorganic C (DIC). Gas-exchange rates are calculated by solving the combined stream transport equation for O2 and DIC. The output is a time-series of aeration rates at the same sampling frequency as the input O2 and C data. Field tests in a 4th-order montane stream in Oregon, USA, indicate that the method is suitable for stream reaches with high downstream gas-concentration gradients and saturation deficits. The mean modeled aeration rate adjusted to 17°C (3.25/h) agreed well with the value of 3.22/h from direct gas injection. Net ecosystem production calculated with the modeled aeration rate (−1.69 g O2 m−2 d−1) was consistent with the result obtained with direct gas injection (−1.60 g O2 m−2 d−1). An assumption of the model is a constant respiration quotient, but results indicated that the respiration quotient may be time variable. Sensitivity analysis indicated that application of the OC method is limited to reaches with a suitable change in combined O2 and CO2 concentration ≥ ∼4 μmol/L and combined O2 and CO2 saturation deficits ≈ 4 μmol/L, characteristic of smaller gaining streams. Preliminary application of the OC method indicates it could be useful to practitioners interested in continuous measurement of gas-exchange rates.

The Effects of Night-time Temperatures on Physiological and Biochemical Traits in Rice

High nighttime temperatures impair rice yield. Additionally, heat stress periods have increased during the last years in the rice areas of the tropics. The aim of this study was to physiologically characterize six genotypes of rice (a commercial cultivar (ʻF60ʼ) and five selected lines (ʻIR 1561ʼ, ʻFLO 2764ʼ, ʻLV447-1ʼ, ʻCT19021ʼ, and ʻLV1401ʼ) subjected to two nighttime temperatures (24 and 30 °C), based on different physiological traits. When the collar formed on leaf 6 of the main stem, one group of six plants in each genotype was subjected to 30 °C from 18:00 to 24:00 hours for eight days, while the other group remained at 24 °C. Differences were found in the interaction between genotype and nighttime temperatures, where a high night temperature reduced leaf photosynthesis by approximately 50% in all genotypes compared to the controls (20 µmol vs. 10 µmol CO2 m-2 s-1, respectively). In general, higher plant respiration was also observed in almost all genotypes when the plants were exposed to 30 °C. However, rice plants of the genotype ʻF60ʼ showed a constant respiration under two different night temperatures. A high nighttime temperature increased the electrolyte leakage and malondialdehyde content only in the ʻLV1401ʼ plants. Plant growth and Fv/Fm ratio were separately conditioned by the night temperature or the genotype factor. A lower total plant dry weight was found at 30 °C (620.36 mg) than in rice plants exposed to 24 °C (254.16 mg). The Fv/Fm ratio was slightly diminished at a high nighttime temperature. These results suggest that physiological variables, such as leaf photosynthesis, plant respiration, malondialdehyde content and leaf photosynthetic pigments, can be considered markers for characterizing tolerant genotypes in earlier growth phases during plant breeding programs.

Influence of the closed suction tube on mechanical ventilation of infants′ end expiratory PETCO2

Objective To explore the influence of closed suction tube on end-tidal carbon dioxide partial pressure (PETCO2) in infants with mechanical ventilation mass ≤10 kg. Methods The study investigated 78 infants with mechanical ventilation of nasal trachea cannula and the closed suction tube was used with constant respirator parameters. Since PETCO2 was continuously monitored for 2 hours before and after the use of closed suction tube, the vital signs and PETCO2 were recorded at every 10 minutes. Results The body temperature, heart rate, breath, systolic pressure, diastolic pressure, and oxygen saturation remained stable before and after the use of closed suction tube. After 60 minutes of using closed suction tube, PETCO2 increased to (41.96±10.90)mmHg (t=-2.914, P<0.05). Conclusions PETCO2 is likely to increase after using closed suction tube for a long time in infants with mechanical ventilation mass ≤10 kg. Key words: Mechanical ventilation; Closed suction tube; Infants; End-tidal carbon dioxide partial pressure

Separating the effect of respiration from the heart rate variability for cases of constant harmonic breathing

Abstract Heart Rate Variability studies are a known measure for the autonomous control of the heart rate. In special situations, its interpretation can be ambiguous, since the respiration has a major influence on the heart rate variability. For this reason it has often been proposed to measure Heart Rate Variability, while the subjects are breathing at a constant respiration rate. That way the spectral influence of the respiration is known. In this work we propose to remove this constant respiratory influence from the heart rate and the Heart Rate Variability parameters to gain respiration free autonomous controlled heart rate signal. The spectral respiratory component in the heart rate signal is detected and characterized. Subsequently the respiratory effect on Heart Rate Variability is removed using spectral filtering approaches, such as the Notch filter or the Raised Cosine filter. As a result new decoupled Heart Variability parameters are gained, which could lead to new additional interpretations of the autonomous control of the heart rate.

Odor Processing by Adult-Born Neurons

The adult mammalian brain is continuously supplied with adult-born neurons in the olfactory bulb (OB) and hippocampus, where they are thought to be important for circuit coding and plasticity. However, direct evidence for the actual involvement of these neurons in neural processing is still lacking. We recorded the spiking activity of adult-born periglomerular neurons in the mouse OB invivo using two-photon-targeted patch recordings. We show that odor responsiveness reaches a peak during neuronal development and then recedes at maturity. Sensory enrichment during development enhances the selectivity of adult-born neurons after maturation, without affecting neighboring resident neurons. Thus, in the OB circuit, adult-born neurons functionally integrate into the circuit, where they acquire distinct response profiles in an experience-dependent manner. The constant flow of these sensitive neurons into the circuit provides it with a mechanism of long-term plasticity, wherein new neurons mature to process odor information based on past demands.

Nutritional status and metabolism of the coral Stylophora subseriata along a eutrophication gradient in Spermonde Archipelago (Indonesia)

Coral responses to degrading water quality are highly variable between species and depend on their trophic plasticity, acclimatization potential, and stress resistance. To assess the nutritional status and metabolism of the common scleractinian coral, Stylophora subseriata, in situ experiments were carried along a eutrophication gradient in Spermonde Archipelago, Indonesia. Coral fragments were incubated in light and dark chambers to measure photosynthesis, respiration, and calcification in a number of shallow reefs along the gradient. Chlorophyll a (chl a), protein content, maximum quantum yield (Fv/Fm), and effective quantum yield (U PS II) were measured on the zooxanthellae, in addition to host tissue protein content and biomass. Photosynthetic rates were 2.5-fold higher near-shore than mid-shelf due to higher areal zooxanthellae and chl a concentrations and a higher photochemical efficiency (U PS II). A 2- and 3-fold increase in areal host tissue protein and biomass was found, indicating a higher nutritional supply in coastal waters. Dark respiration, however, showed no corresponding changes. There was a weak correlation between calcification and photosynthesis (Pearson r = 0.386) and a lack of metabolic stress, as indicated by constant respiration and Fv/Fm and the ‘‘clean’’ and healthy appearance of the colonies in spite of high turbidity in near-shore waters. The latter suggests that part of the energetic gains through increased auto- and heterotrophy were spent on metabolic expenditures, e.g., mucus production. While coastal pollution is always deleterious to the reef ecosystem as a whole, our results show that the effect on corals may not always be negative. Thus, S. subseriata may be one of the few examples of corals actually profiting from land-based sources of pollution.

Experimental validation of heterogeneity-corrected dose-volume prescription on respiratory-averaged CT images in stereotactic body radiotherapy for moving tumors

The purpose of this study was to experimentally assess the validity of heterogeneity-corrected dose-volume prescription on respiratory-averaged computed tomography (RACT) images in stereotactic body radiotherapy (SBRT) for moving tumors. Four-dimensional computed tomography (CT) data were acquired while a dynamic anthropomorphic thorax phantom with a solitary target moved. Motion pattern was based on cos6 (t) with a constant respiration period of 4.0 sec along the longitudinal axis of the CT couch. The extent of motion (A1) was set in the range of 0.0–12.0 mm at 3.0-mm intervals. Treatment planning with the heterogeneity-corrected dose-volume prescription was designed on RACT images. A new commercially available Monte Carlo algorithm of well-commissioned 6-MV photon beam was used for dose calculation. Dosimetric effects of intrafractional tumor motion were then investigated experimentally under the same conditions as 4D CT simulation using the dynamic anthropomorphic thorax phantom, films, and an ionization chamber. The passing rate of γ index was 98.18%, with the criteria of 3 mm/3%. The dose error between the planned and the measured isocenter dose in moving condition was within ± 0.7%. From the dose area histograms on the film, the mean ± standard deviation of the dose covering 100% of the cross section of the target was 102.32 ± 1.20% (range, 100.59–103.49%). By contrast, the irradiated areas receiving more than 95% dose for A1 = 12 mm were 1.46 and 1.33 times larger than those for A1 = 0 mm in the coronal and sagittal planes, respectively. This phantom study demonstrated that the cross section of the target received 100% dose under moving conditions in both the coronal and sagittal planes, suggesting that the heterogeneity-corrected dose-volume prescription on RACT images is acceptable in SBRT for moving tumors.

Respiration of midges (Diptera; Chironomidae) in British Columbian lakes: oxy‐regulation, temperature and their role as palaeo‐indicators

Summary1. The specific respiration rate of 13 chironomid taxa and Chaoborus were measured to test the hypothesis of the relation between a species’ ability to regulate their oxygen uptake and their distributional patterns among nine study lakes in British Columbia, Canada.2. Respiration patterns of individual taxa were modelled using piecewise linear regression with break point and simple hyperbolic functions. Three types of respiration curves were identified: (i) classical oxy‐conformers (e.g. littoral Cricotopus) which cannot sustain a sufficient oxygen uptake with decreasing oxygen availability; (ii) oxy‐regulators (e.g. profundal Chironomus) which can regulate and maintain a constant respiration until a certain critical point and (iii) oxy‐stressors (Micropsectra) which increase their respiration rate with decreasing oxygen availability until a critical point.3. Respiration was measured at two different temperatures (10 and 20 °C), and over the range of oxygen saturation conditions studied here (0–90%) mean Q10 values varied from 1.3 to 2.5.4. The results show that different chironomid taxa have varying sensitivity to low oxygen concentrations and different respiratory responses to increased temperature. The critical point increased to higher oxygen saturation for six taxa, decreased for one taxon and was unchanged for two taxa.5. The results illustrate one of the possible biological mechanisms behind the use of chironomids as temperature and climate indicators in palaeoecological studies by exploring the link between temperature and respiration physiology.

Respiration rates of fresh-cut bell peppers under supertamospheric and low oxygen with or without high carbon dioxide

The respiration rates of fresh-cut bell peppers under diverse high and low O 2 levels, with or without 20 kPa CO 2, at 2, 7 and 14 °C, were studied. Weight loss and off-odor development were also monitored. A constant respiration rate of pepper dices throughout 3 days under different conditions was found. Fresh-cut peppers exposed to 0, 0.5, 1, 3 and 9 kPa O 2 (all CO 2-free), and to 0 kPa O 2 + 20 kPa CO 2, had a lower respiration rate than peppers in the range 20–100 kPa O 2 with or without CO 2. Under high O 2, 20 kPa CO 2 increased the respiration rate by about 20–40% compared to that in free-CO 2 atmospheres, this effect being lower at low temperature. High O 2 had little (at 14 °C) or no effect (at 2 and 7 °C) in stimulating both CO 2 production and O 2 consumption compared to normal air. High CO 2 in the range 20–100 kPa O 2 increased the respiratory activity of pepper dices, probably because physiological injury occurred at 14 °C. However, 20 kPa CO 2 combined with superatmospheric O 2 neither induced a poor visual appearance nor off-odors. Consequently 50–80 kPa O 2 combined with 20 kPa CO 2 could be used in innovative modified atmosphere packaging of pepper dices to avoid fermentation and inhibit growth of spoilage microorganisms.

Respiratory sinus arrhythmia as a second order system

The presented study describes the influence of respiration on heart rate, under controlled respiration conditions. In addition, this study makes a comparison of a simple physical model, the spring-mass system, with the biophysics of respiration. It is possible to use the equations describing the behaviour of the respiratory system, under certain conditions, and analyse them in a way similar to the equations that describe the physical spring-mass system. The results of the heart rate and respiration measurements effected on 10 subjects at various respiration frequencies show us that the heart rate behaves as a second order system within the boundary conditions during a longer period of constant respiration. The results also show that the heart rate behaves as a second order system within the intermediate mode during short time intervals when there is no respiration.

Changes in respiration of fresh-cut butterhead lettuce under controlled atmospheres using low and superatmospheric oxygen conditions with different carbon dioxide levels

The effect of different O 2 levels from 0 to 100 kPa in combination with 0, 10 and 20 kPa CO 2 on the respiration metabolism of greenhouse grown fresh-cut butter lettuce was studied. Controlled atmospheres of 20 or 75 kPa O 2 with 0 or 10 kPa CO 2 showed a constant respiration rate during the first 2–4 days at different temperatures (1, 5 and 9 °C). Therefore, constant respiration rates during a short period of 2–4 days could be considered as valid for a large part of the commercial life of, for instance, a modified atmosphere package development. The fresh-cut lettuce exposed to low O 2 levels (2–10 kPa) combined with moderate to high CO 2 levels (10 and 20 kPa) had a higher respiration rate than when 20–100 kPa O 2 were used. Moderate CO 2 levels (10 kPa) reduced the respiration rates of fresh-cut lettuce 20–40% at 9 °C. This effect was less noticed at lower temperatures. Gas composition with high CO 2 levels (20 kPa) probably caused a metabolic disorder increasing the respiration rate of fresh-cut butter lettuce. It was concluded that 80 kPa O 2 must be used in modified atmosphere packaging (MAP) to avoid fermentation of fresh-cut butter lettuce in combination with 10–20 kPa CO 2 for reducing their respiration rate.

Role of carbohydrate supply in white and brown root respiration of ponderosa pine.

• Respiration of intact ponderosa pine (Pinus ponderosa) fine roots (<2.5mm) was measured to determine the role of recently fixed carbohydrate in maintaining root metabolism of growing white (WR) and recently suberized brown roots (BR). • The CO2 efflux and O2 uptake of individual roots were followed continuously over 24h after carbohydrate supply was altered by exposing shoots to light/dark treatments and by root excision. • In situ respiration of individual WR and BR averaged 86.0±2.6 and 21.1±1.5mol CO2 g-1 h-1 , respectively. Growth respiration was estimated to be approximately two-thirds the rate of WR respiration. Attached WR and BR respiration did not decline significantly over 24h under continuous light. The WR respiration significantly decreased during a dark period. All roots maintained relatively constant respiration rates for at least 6h after excision. Respiratory quotient (RQ; CO2 :O2 ) was not different between attached (0.84±0.014) and detached (0.85±0.017) roots. CO2 environment of the cuvette did not influence WR or BR respiration. • The WR appear to be more sensitive to supply of current photosynthate than BR. Shoot light environment needs to be considered when measuring root and soil CO2 efflux.

作物葉の総光合成と純光合成における同化細胞層ＣＯ２移動に関する理論的一考察

The CO2 mass transfer problem of the assimilation cell phase of the crop leaf in the gross photosynthesis process was solved by the use of analytical procedures for net photosynthesis in the previous investigation (Komori and Ikemoto, 1999).The solutions were applied to evaluate the CO2 gross mass transfer coefficient kL0, the gross photosynthetic reaction rate constant k10 and the CO2 concentration profile CA(z, t) in the assimilation cell phase with a constant respiration rate k0 for the case of rice. The summary is as follows:1) Exact solutions for CA(z, t), the CO2 flux NA0, kL0 and the gross photosynthetic rate RAT0 are simplified to Eq. (13) through Eq. (16). These approximate solutions are available to obtain the relation of the CO2 mass transfer mechanism between the gross and the net photosynthesis in the assimilation celll phase.2) Equation (22) or Eq. (39) gives the correlation of the gross and the net photosynthesis with the CO2 mass transfer rate. Equation (22) suggests that k0 has no influence on the gas phase CO2 mass transfer coefficient kG and for the over-all CO2 mass transfer coefficient, Eq. (39) provides Eq. (40). Moreover, Eqs. (22) and (39) indicate that the graphical method (Komori and Ikemoto, 1999) is appropriate for estimation of kL and kG.3) Figure 3, generated from Eq. (22) or Eq. (39), shows the relationship between k10 and the net photosynthetic reaction rate constant k1, and is also the graphical method to estimate k10 from the net photosynthetic rate RAT and k0. Following the analytical discussion of Eq. (21) through Eq. (29) the k10-RAT curve in Fig. 3, shows that for assimilation of the crop leaf, the practical gross photosynthesis is biophysically different from the substantial net photosynthesis.4) In order to quantitatively evaluate the characteristics of the photosynthetic reaction, the assimilation cell effectiveness factor Ef0 (Bird et al., 1960; Ohtake, 1963), defined by Eq. (50), was introduced. The Ef0 curve in Fig. 9 indicates the equilibrium point, kGb=kGs, the transition point, kL=HkG for the CO2 mass transfer resistance and the terminal point of RATmax at the maximum RAT in the region of 0≤RAT≤RATmax. In addition, Ef0 suggests that the photosynthetic reaction is very fast and can be performed near the surface of the assimilation cell phase.

The relationship between respiration and chip color during long-term storage of potato tubers

Processing potatoes, both sprout inhibited and untreated, were evaluated for respiration rate and chip color during storage under commercial conditions (12 C, approximately 95% relative humidity, in darkness) following three growing seasons. While absolute respiration rates varied depending upon growing season and treatment, all cultivars and treatments studied during the 1995, 1996, and 1997 storage seasons showed similar respiration profiles. The initial stage following curing and sprout inhibition treatment (if applied) showed essentially constant respiration rates for a period of time varying from two to 15 weeks, depending upon growing season, treatment and cultivar. This was followed by a stage that showed a linear increase in respiration rates. In some cases the respiration rates eventually stabilized, or decreased. There was an apparent correlation between respiration trends and chip color changes in most cases, though the statistical significance varied between cultivars and seasons. Qualitative analysis of the data showed that the point at which respiration rates began to increase coincided with the onset of the decline in chip color quality. These trends suggest that measurement of tuber respiration may provide a non-destructive andin situ method to predict changes in processing quality of stored potato tubers.