Oscillations of the internal CO2 concentration in tobacco leaves transferred to low CO2

Measurement of the internal CO2 concentration (Ci) in tobacco leaves using a fast-response CO2 exchange system showed that in the light, switching from 350 μL L−1 to a low CO2 concentration of 36.5 μL L−1 (promoting high photorespiration) resulted in the Ci oscillating near the value of CO2 compensation point (Γ*). The oscillations are highly irregular, the range of Ci varying by 2–4 μL L−1 in substomatal cavities with a period of a few seconds. The statistical properties of the time series became stationary after a transient of ∼100 s following transfer to low CO2. Attractor reconstruction shows that the observed oscillations are not chaotic but exhibit stochastic behavior. The period of oscillations is consistent with the duration of photorespiratory post-illumination burst (PIB). We suggest that the observed oscillations may be due to a similar mechanism to that which leads to PIB, and may play a role in switching mitochondrial operation between oxidation of the photorespiratory glycine and of the tricarboxylic acid cycle substrates.