Inhibition of photosynthesis by heat stress: the activation state of Rubisco as a limiting factor in photosynthesis

Abstract

Although the catalytic activity of Rubisco increases with temperature, the low affinity of the enzyme for CO(2) 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 degrees C. Inhibition of photosynthesis by moderate heat stress (i.e. 30-42 degrees 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 CO(2) indicate that electron transport activity is not limiting at temperatures that inhibit CO(2) fixation. Instead, recent evidence shows that inhibition of net photosynthesis correlates with a decrease in the activation state of Rubisco in both C(3) and C(4) 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.

Interactions between temperature, drought and stomatal opening in legumes

“…Previously, elevated temperatures were shown to negatively affect photosynthesis (Feller et al, 1998;Law and Crafts-Brandner, 1999;Haldimann and Feller, 2004), influencing leaf metabolism primarily through Rubisco activase properties and Rubisco activation state (Feller et al, 1998;Crafts-Brandner and Salvucci, 2000;Feller, 2004, 2005). It was also demonstrated that plants increase stomatal conductance under high temperatures (Salvucci and Crafts-Brandner, 2004). However, our results show that stomatal response to heat and drought is complex: legumes respond to moderate stress by closing stomata or causing irregular conductance and to high temperature stress by increasing stomatal conductance, even under drought.…”

Impacts of Heat Stress on Wheat: A Critical Review

“…High temperature result in the decreased solubility of O 2 and CO 2 however, increased photorespiration and lower photosynthesis is the result of increased level of CO 2 than O 2 [71]. In addition, decreased activity of Rubisco at high temperature is primarily due to inhibition of the enzyme Rubisco activase which becomes unable to overcome the inherently faster rates of Rubisco inactivation [72][73][74]. Amongst the photosynthetic apparatus photosystem II being more tolerant to drought stress than heat relatively plays a key role in leaf photosynthesis [75].…”

Physiological adaptive mechanisms of plants grown in saline soil and implications for sustainable saline agriculture in coastal zone

“…This technology will extend our knowledge about PSI and the cooperation between PSI and PSII and give us a more thorough and comprehensive picture about the operating mechanisms of plant photosynthetic apparatus Yan et al 2012). It is noticeable that CO 2 fixation process is also a critical step for photosynthesis (Salvucci and Crafts-Brandner 2004). Rubisco enzyme and its activation enzyme play a key role in this step, and their activities and contents can be measured, but the procedure is relatively complex.…”