CO₂ Inhibits Respiration in Leaves of Rumex crispus L.

Abstract

Curly dock (Rumex crispus L.) was grown from seed in a glasshouse at an ambient CO2 partial pressure of about 35 pascals. Apparent respiration rate (CO2 efflux in the dark) of expanded leaves was then measured at ambient CO2 partial pressure of 5 to 95 pascals. Calculated intercellular CO2 partial pressure was proportional to ambient CO2 partial pressure in these short-term experiments. The CO2 level strongly affected apparent respiration rate: a doubling of the partial pressure of CO2 typically inhibited respiration by 25 to 30%, whereas a decrease in CO2 elicited a corresponding increase in respiration. Respiration MeasurementsPlants of approximately 4 weeks of age were removed from the growth system at the end of the photoperiod, transferred to a flask containing 1 L of aerated nutrient solution, and kept in the dark overnight in the laboratory. The following morning, the youngest fully expanded leaf was enclosed in a temperature-controlled gas exchange cuvette similar to that described by Field et al. (7). This attached leaf and the remainder of the plant were kept in the light (PPFD = 800 Omol m-2 s-') at 35 Pa CO2 for 3 h, after which the light was turned off and the leaf cuvette and plant were covered with a light-tight box. Leaf temperatures were maintained at either 15.0 ± 0.2 or 25.0 ± 0.2°C during each experiment.The gas exchange system described by Bloom et al. (3) was used to regulate and monitor CO2 and water vapor exchange. The IRGA (Horiba VIA-SOOR) was calibrated (4) over the range of 5 to 95 Pa CO2. The CO2 partial pressure of the air entering the leaf cuvette was regulated by mixing CO2-free air with air containing 1% C02 using mass flow controllers (Tylan FC-260). Gas exchange calculations followed von Caemmerer and Farquhar (12). Leaf intercellular CO2 partial pressure was given by: Cj = Ca + P RA/gc,where P is cuvette air pressure (Pa), RA is the measured leaf CO2 flux area density (i.e. apparent respiration rate on an area basis; mol CO2 efflux m-2 s-'), and gc is leaf CO2

Direct Inhibition of Plant Mitochondrial Respiration by Elevated CO2

“…The results of this study show that the reported direct inhibitory effect of increasing C, on plant respiration (Amthor et al, 1992) is also seen in isolated plant mitochondria. The effect was mediated at least in part by inhibition of Cyt c oxidase and SDH.…”

“…112, 1996 O u r results suggest that a t least part of the so-called direct effect of elevated C, on respiration reported in tissues (e.g. Amthor et al, 1992) m a y b e located a t the leve1 of the mitochondria. A n increase i n the concentration of CO, equivalent to 360 p L L-' inhibited the rate of mitochondrial O, uptake by 10 to 15%, depending on the substrate utilized.…”

“…A reversible inhibition of CO, evolution by Rumex crispus leaves was observed when C, was increased stepwise through the range of O to 1000 pL L-' (Amthor et al, 1992). Inhibition of respiration by increasing C, has also been reported in whole plants (Bunce, 1990;Ryle et al, 1992), leaves (Reuveni and Gale, 1985;Bunce, 1990;El Kohen et al, 1991;Amthor et al, 1992;Byrd et al, 1992;Thomas and Griffin, 1994;Ziska and Bunce, 1994), roots (Reuveni and Gale, 1985;Palta and Nobel, 1989;Qi et al, 1994), microorganisms (Koizumi et al, 1991), and animal tissues (Palet et al, 1991).…”

The effect of elevated CO2 and grazing by Gastrophysa viridula on the physiology and regrowth of Rumex obtusifolius

“…There was no effect of growth CO, concentration and, although a significant amount of damage was evident on the leaves from the herbivory treatments, the rates of respiration did not appear to have been affected. Measurements made on Rumex crispus plants indicated that increasing the CO., mole fraction over the range 350-650/^mol mol~' reduced respiration by 25-30 °o (Amthor, Koch & Bloom, 1992). Our measurements differ from those of Amthor et al (1992) in that our plants developed under ambient and elevated concentrations of CO, rather than being subjected to them during the course of the measurements.…”

“…Measurements made on Rumex crispus plants indicated that increasing the CO., mole fraction over the range 350-650/^mol mol~' reduced respiration by 25-30 °o (Amthor, Koch & Bloom, 1992). Our measurements differ from those of Amthor et al (1992) in that our plants developed under ambient and elevated concentrations of CO, rather than being subjected to them during the course of the measurements. In cases where plants have been grown in ambient and elevated CO, no consensus has emerged (Amthor, 1991), with both significant increases and decreases (e.g.…”