Thylakoid membrane responses to moderately high leaf temperature in Pima cotton
Article first published online: 1 MAR 2004
Plant, Cell & Environment
Volume 27, Issue 6, pages 725–735, June 2004
How to Cite
SCHRADER, S. M., WISE, R. R., WACHOLTZ, W. F., ORT, D. R. and SHARKEY, T. D. (2004), Thylakoid membrane responses to moderately high leaf temperature in Pima cotton. Plant, Cell & Environment, 27: 725–735. doi: 10.1111/j.1365-3040.2004.01172.x
- Issue published online: 1 MAR 2004
- Article first published online: 1 MAR 2004
- Received 13 November 2003; received in revised form 15 December 2003; accepted for publication 16 December 2003.
- adenosine 5′-triphosphate;
- heat stress;
- NADP-malate dehydrogenase;
- Rubisco activation
Photosynthesis is inhibited by high temperatures that plants are likely to experience under natural conditions. Both increased thylakoid membrane ionic conductance and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) deactivation have been suggested as the primary cause. The moderately heat-tolerant crop Pima S-6 cotton (Gossypium barbadense) was used to examine heat stress-induced inhibition of photosynthesis. Previous field-work indicated that moderate heat stress (T = 35–45 °C) is associated with very rapid leaf temperature changes. Therefore, a system was devised for rapidly heating intact, attached leaves to mimic natural field heat-stress conditions and monitored Rubisco activation, carbon-cycle metabolites, thylakoid ionic conductance, and photosystem I activity. As a proxy for NADPH and stromal redox status the activation state of NADP-malate dehydrogenase (NADP-MDH) was measured. In dark-adapted cotton leaves, heating caused an increase in thylakoid permeability at temperatures as low as 36 °C. The increased permeability did not cause a decline in adenosine 5′-triphosphate (ATP) levels during steady-state or transient heating. Rapid heating caused a transient decline in ribulose 1,5-bisphosphate without a decrease in Rubisco activation. Sustained heating caused a decline in Rubisco activation and also oxidized the stroma as judged by NADP-MDH activation and this is hypothesized to result from increased cyclic photophosphorylation, explaining the maintenance of ATP content in the face of increased thylakoid membrane ion leakiness.