The 2002 Annual Symposium of the Southern Section of the American Society of Plant Biologists took place at the University of Georgia on March 4, 2002. The theme of the colloquium was ‘Mechanisms for Regulation of Plant Metabolism’. This issue of Physiologia Plantarum contains three papers based on the invited lectures. Generous support for these lectures was provided by Pioneer Hi Bred International Inc., Syngenta Crop Protection, Inc., and the American Society of Plant Biologists.
Inhibition of photosynthesis by heat stress: the activation state of Rubisco as a limiting factor in photosynthesis
Article first published online: 6 JAN 2004
Volume 120, Issue 2, pages 179–186, February 2004
How to Cite
Salvucci, M. E. and Crafts-Brandner, S. J. (2004), Inhibition of photosynthesis by heat stress: the activation state of Rubisco as a limiting factor in photosynthesis. Physiologia Plantarum, 120: 179–186. doi: 10.1111/j.0031-9317.2004.0173.x
Edited by T. Sherman and P. Gardeström
- Issue published online: 6 JAN 2004
- Article first published online: 6 JAN 2004
- Received 13 November 2002; revised 24 February 2003
Although the catalytic activity of Rubisco increases with temperature, the low affinity of the enzyme for CO2 and its dual nature as an oxygenase limit the possible increase in net photosynthesis with temperature. For cotton, comparisons of measured rates of net photosynthesis with predicted rates that take into account limitations imposed by the kinetic properties of Rubisco indicate that direct inhibition of photosynthesis occurs at temperatures higher than about 30°C. Inhibition of photosynthesis by moderate heat stress (i.e. 30–42°C) is generally attributed to reduced rates of RuBP regeneration caused by disruption of electron transport activity, and specifically inactivation of the oxygen evolving enzymes of photosystem II. However, measurements of chlorophyll fluorescence and metabolite levels at air-levels of CO2 indicate that electron transport activity is not limiting at temperatures that inhibit CO2 fixation. Instead, recent evidence shows that inhibition of net photosynthesis correlates with a decrease in the activation state of Rubisco in both C3 and C4 plants and that this decrease in the amount of active Rubisco can fully account for the temperature response of net photosynthesis. Biochemically, the decrease in Rubisco activation can be attributed to: (1) more rapid de-activation of Rubisco caused by a faster rate of dead-end product formation; and (2) slower re-activation of Rubisco by activase. The net result is that as temperature increases activase becomes less effective in keeping Rubisco catalytically competent. In this opinionated review, we discuss how these processes limit photosynthetic performance under moderate heat stress.