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- Title
Rapid heating of intact leaves reveals initial effects of stromal oxidation on photosynthesis.
- Authors
SCHRADER, STEPHEN M.; KLEINBECK, KYLE R.; SHARKEY, THOMAS D.
- Abstract
Heat stress in leaves under natural conditions is characterized by rapid fluctuations in temperature. These fluctuations can be on the order of 10 °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.
- Subjects
EFFECT of heat on plants; PHYSIOLOGICAL effects of heat; LEAF anatomy; EFFECT of temperature on plants; OXYGENASES; PHOSPHATES; MALATE dehydrogenase; DEHYDROGENASES; OXIDOREDUCTASES
- Publication
Plant, Cell & Environment, 2007, Vol 30, Issue 6, p671
- ISSN
0140-7791
- Publication type
Article
- DOI
10.1111/j.1365-3040.2007.01657.x