The time course of acclimation to the stress of triose phosphate use limitation

Triose-phosphate utilization (TPU) limits the maximum rate at which plants can photosynthesize. However, TPU is almost never found to be limiting photosynthesis under ambient conditions for plants. This, along with previous results showing adaptability of TPU at low temperature, suggest that TPU capacity is regulated to be just above the photosynthetic rate achievable under the prevailing conditions. A set of experiments were performed to study the adaptability of TPU capacity when plants are acclimated to elevated CO2 concentrations. Plants held at 1500 ppm CO2 were initially TPU-limited. After 30 hours, they no longer exhibited TPU limitations, but they did not elevate their TPU capacity. Instead, the maximum rates of carboxylation and electron transport declined. A time course of regulatory responses was established. A step increase of CO2 first caused PSI to be oxidized, but after 40 s, both PSI and PSII had excess electrons as a result of acceptor-side limitations. Electron flow to PSI slowed, and the proton motive force increased. Eventually, non-photochemical quenching reduced electron flow sufficiently to balance the TPU limitation. Over several minutes rubisco deactivated contributing to regulation of metabolism to overcome the TPU limitation.

Methods
This data was collected in laboratory in East Lansing MI using LI-COR LI-6800 instruments modified to be able to take optical and fluorescent measurements. Rubisco activation measurements were collected via scintillation counts for radioactive C14. Data was split, processed using R scripts, and then collated into tables that are presented in this dataset.