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Updated: Jul 15, 2026

High Throughput Image-Based Phenotyping for Determining Morphological and Physiological Responses to Single and Combined Stresses in Potato
Published on: June 7, 2024
Rapid heating of intact leaves reveals initial effects of stromal oxidation on photosynthesis
Stephen M Schrader1, Kyle R Kleinbeck, Thomas D Sharkey
1Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA. tsharkey@wisc.edu
Abstract:
Heat stress in leaves under natural conditions is characterized by rapid fluctuations in temperature. These fluctuations can be on the order of 10 degrees C in 7 s. By using a specially modified gas-exchange chamber, these conditions were mimicked in the laboratory to analyse the biochemical response to heat spikes. The decline in ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) activity during prolonged heat stress is generally associated with an increase in ribulose 1,5-bisphosphate (RuBP) levels. However, rapid heating caused an initial decline in RuBP which was subsequently followed by a small decline in Rubisco carbamylation. The ratio of RuBP to Rubisco sites declined from a saturating concentration to a sub-saturating concentration, providing a possible mechanism for the decarbamylation of Rubisco. If RuBP is saturating (>1.8 RuBP Rubisco site(-1)), it acts as a cap on the catalytic site and keeps Rubisco activated. Measurements of triose-phosphate levels and NADP-malate dehydrogenase activation (a stromal redox proxy) indicated that the regeneration of RuBP by the Calvin cycle was limited by the availability of redox power.
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