Abstract
To clarify biochemical and molecular mechanisms of shift of optimum temperature for photosynthesis, we grew spinach (Spinacia oleracea) at 15C or 30C and analyzed various photosynthetic properties.
Temperature optima of RuBP carboxylation, assessed by the gas exchange techniques, were 18C and 24C in the leaves grown at 15C and 30C, respectively, although temperature dependence of carboxylation has been believed to be unaffected by growth temperature. Results of the Two-dimensional gel electrophoresis of Rubisco revealed significant differences in the isoelectric point in Rubisco small subunits depending on the growth temperature. It is likely that, in spinach grown at the lower temperature, expression of isozyme(s) of Rubisco small subunits having greater activity at the lower temperature, or some post-translational modification of Rubisco small subunits contributes to the downward shift in the optimum temperature for photosynthesis.
