Abstract
While interspecific variation in the temperature response of photosynthesis is well documented, the underlying physiological mechanisms remain unknown. Moreover, mechanisms related to species-dependent differences in photosynthetic temperature acclimation are unclear. We compared photosynthetic temperature acclimation in 11 crop species differing in their cold tolerance, which were grown at 15 degrees C or 30 degrees C. Cold-tolerant species exhibited a large decrease in optimum temperature for the photosynthetic rate at 360 microL L(-1) CO(2) concentration [Opt (A(360))] when growth temperature decreased from 30 degrees C to 15 degrees C, whereas cold-sensitive species were less plastic in Opt (A(360)). Analysis using the C(3) photosynthesis model shows that the limiting step of A(360) at the optimum temperature differed between cold-tolerant and cold-sensitive species; ribulose 1,5-bisphosphate carboxylation rate was limiting in cold-tolerant species, while ribulose 1,5-bisphosphate regeneration rate was limiting in cold-sensitive species. Alterations in parameters related to photosynthetic temperature acclimation, including the limiting step of A(360), leaf nitrogen, and Rubisco contents, were more plastic to growth temperature in cold-tolerant species than in cold-sensitive species. These plastic alterations contributed to the noted growth temperature-dependent changes in Opt (A(360)) in cold-tolerant species. Consequently, cold-tolerant species were able to maintain high A(360) at 15 degrees C or 30 degrees C, whereas cold-sensitive species were not. We conclude that differences in the plasticity of photosynthetic parameters with respect to growth temperature were responsible for the noted interspecific differences in photosynthetic temperature acclimation between cold-tolerant and cold-sensitive species.
Highlights
While interspecific variation in the temperature response of photosynthesis is well documented, the underlying physiological mechanisms remain unknown
When plants were grown at 15°C, the mean optimum temperature for at 360 mL L21 CO2 concentration [Opt (A360) [Opt (A360)] was significantly lower in cold-tolerant species (22.3°C 6 2.2°C) than in coldsensitive species (28.3°C 6 2.4°C; Table I)
All species showed an increase in Opt (A360) with increasing growth temperature, except for Vicia faba (Supplemental Table S1)
Summary
While interspecific variation in the temperature response of photosynthesis is well documented, the underlying physiological mechanisms remain unknown. Alterations in parameters related to photosynthetic temperature acclimation, including the limiting step of A360, leaf nitrogen, and Rubisco contents, were more plastic to growth temperature in cold-tolerant species than in cold-sensitive species. These plastic alterations contributed to the noted growth temperature-dependent changes in Opt (A360) in cold-tolerant species. We conclude that differences in the plasticity of photosynthetic parameters with respect to growth temperature were responsible for the noted interspecific differences in photosynthetic temperature acclimation between cold-tolerant and cold-sensitive species. In the case that the optimum temperature is determined by the intersection of the temperature dependences of Ac and Ar, the optimum temperature can shift by changes in the balance between Ac and Ar even when the optimum temperatures for these two partial reactions do not change
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