Carbon dioxide exchange rate

Figure 17.13 Carbon dioxide exchange rates of 20 potato stands grown at 865 or 655 (xmol s PAR. Positive values reflect net photosynthetic rates during the light period and negative values reflect respiration rates during the dark period (source Wheeler et al., 2008a).

Figure 17.14 Effect of changes in photoperiod on the carbon dioxide exchange rate of a 20 potato stand. On day 58, the photoperiod was changed from 12-h to 24-h (i.e., continuous light), which resulted in drop in the instantaneous photosynthetic rates. Switching back to 12h at day 61 allowed photosynthetic rates to slowly increase. A similar effect was observed between days 75 and 77 (source Wheeler et al., 2008a).

Figure 17.15 Carbon dioxide exchange rate (net photosynthetic rate) of a 20 potato stand at different CO2 concentrations. The photosynthetic rates saturated above 1200 ppm while the CO2 compensation point occurred at 97 ppm (source Wheeler et al., 2008a).

Walton, A., M. Ergin, and D. D. Markness (1970). Carbon-14 concentrations in the atmosphere and carbon dioxide exchange rates. J. Geophys. Res. 75, 3089-3098. 

In ambient air, 2nd leaf (LPI-2) showed higher Net Carbon dioxide Exchange Rate (NCER) as well as RuBP carboxylase activity than the 5th leaf (LPI-5I) of the same age, while the 12 day old leaf had higher NCER and RuBP carboxylase activity than the 18 day old 5th leaf (LPI-5II). On enrichment with 600 and 900 ul 1 1 CO2 2nd leaf showed a much higher NCER than the 5th leaf of same age. Similarly, the younger 5th leaf showed more response than the older 5th leaf. It appears that leaf position as well as leaf age, both affect the response to elevated CO2 but the leaf position is more effective of the two (Table 1). 

Fig. 3. Carbon dioxide exchange rates in light in percent of normal (ordinate) thalli of Ramalina maciformis after different periods of desiccation (abscissa) under different humidity conditions, (a) the water content of the thalli remained at 1% (b) at 2.5% (c)at 15% of the dry weight. Photosynthesis was measured after 1.5 hours imbibition (C) and after 4 hours imbibition (B) subsequent to the desiccation period. (A) represents maximum values within the time of the post culture (From Lange, 1969).

Baldocchi, D. 2003. Assessing the eddy covariance technique for evaluating carbon dioxide exchange rates of ecosystems Past, present and future. Global Change Biology 9 479-492. 

Goldman J.C. and Dennett M.R. (1983) Carbon dioxide exchange between air and seawater No evidence for rate catalysis. Science 220,199-201. 

Oxygen exchange between [Cr(NH3)s(OH2)] + and solvent water is catalysed by carbon dioxide. The rate law and appropriate rate constants have been determined. The mechanism involves oxygen-atom scrambling through formation of an intermediate carbonate complex. - ... 

A great drawback in many biochemical experiments is the rapid exchange between carbon dioxide and water. Kats and Lapteva (1958) have measured the kinetics of this exchange under various conditions and found it to be complete in approximately 20 hours at 12.5°C. and in 3 hours at 90°. Rothberg and Steinberg (1957) have examined the effect of the shape of the vessel on the rate of isotopic exchange between carbon dioxide and water at 37° C. Mills and Urey (1940) found that carbon dioxide exchanges completely with water in 7 minutes at 30°C. and over an hour at 0°C. 

The amount of carbon dioxide in the atmosphere is proportional to the partial pressure. Thus if partial pressure is expressed in units of the present level, the amount will become 56 X 1015 pco2 moles, where pco2 is the partial pressure of carbon dioxide. Expressing the reservoir in units of 1015 moles and the exchange rate in 1015 moles/y, the equation for the time rate of change of carbon dioxide partial pressure, assuming no other sources or sinks, becomes... 

Carbonic anhydrase presents an instructive case where the catalytic efficiency is so great (kcat > 10 s- ) that proton transfer becomes rate-limiting. The rate was found to depend on the concentration of the protonated form of buffers in the solution. Indeed, Silverman and Tu adduced the first convincing evidence for the role of buffer in carbonic anhydrase catalysis through their observation of an imidazole buffer-dependent enhancement in equilibrium exchanges of oxygen isotope between carbon dioxide and water. The effect is strictly on kcat, and is unaffected because the latter is... 

The detailed process design is familiar to students of chemical engineering, and includes specifying the source of the raw material water the equipment to be used, such as filtration, reverse osmosis, charcoal absorption, ozone treatment, ion exchanger, and pumps the processing conditions, such as flow rates and temperatures and the plant flow sheet. The detailed product design plan for this simplest of products includes the composition of this bottled water, with special attention to the concentrations of compounds such as sodium and carbon dioxide, suspended matter, and microbes, with special emphasis on the appearance and smell. 

Purification of Air Prior to Liquefaction. Separation of air by cryogenic fractionation processes requires removal of water vapor and carbon dioxide to avoid heat exchanger freeze-up. Many plants today are using a 13X (Na-X) molecular sieve adsorbent to remove both water vapor and carbon dioxide from air in one adsorption step. Since there is no necessity for size selective adsorption, 13X molecular sieves are generally preferred over type A molecular sieves. The 13X molecular sieves have not only higher adsorptive capacities but also faster rates of C02 adsorption than type A molecular sieves. The rate of C02 adsorption in a commercial 13X molecular sieve seems to be controlled by macropore diffusion 37). The optimum operating temperature for C02 removal by 13X molecular sieve is reported as 160-190°K 38). 

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