The time course of acclimation to the stress of triose phosphate use
limitation
Authors: Alan M. McClain1,2,3, Jeffrey A.
Cruz1, David M. Kramer1,2, Thomas D.
Sharkey1,2,4
1Michigan State University-Department of Energy Plant
Research Laboratory, East Lansing MI 48824 USA;2Department of Biochemistry and Molecular Biology,
Michigan State University, East Lansing MI 48824 USA;3 Plant Biotechnology for Health and Sustainability,
Michigan State University, East Lansing MI 48824 USA;4 Plant Resilience Institute, Michigan State
University, East Lansing MI 48824 USA.
ORCIDs
Alan M. McClain. 0000-0002-4989-1436
Jeffrey A. Cruz
David M. Kramer
Thomas D. Sharkey. 0000-0002-4423-3223
Corresponding author Thomas D. Sharkey, email tsharkey@msu.edu Phone +1
(517) 353-3257
Abstract
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 CO2concentrations. 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
timecourse 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.
KEY WORDS
Thylakoid ATP synthase, Energy-dependent exciton quenching,
Photosynthetic control, Rubisco activation, triose phosphate use (TPU)