Effects of growth-light quantity, growth-light quality and CO2 concentration on Rubisco deactivation during low PFD or darkness

摘要

The effects of CO2 concentration and the effects of growth-light conditions on ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) deactivation were examined for spinach (Spinacea oleracea). Rubisco deactivation kinetics and the degree that Rubisco activation limited the rise in photosynthesis following an increase in photon flux density (PFD) were determined from gas-exchange time courses. There were no significant differences in the apparent relaxation time for Rubisco deactivation among leaves exposed to high or low CO2 (50 or 1000μmol mol-1) and low PFD (170μmol m-2 s-1) or darkness. However, when PFD was increased to 1700μmol m-2 s-1 following a period of low PFD or darkness, leaves exposed to low CO2Xlow PFD showed a lower contribution to the photosynthetic induction process by the activation of Rubisco than leaves exposed to the other treatments. For the growth-light experiments, spinach was grown under high PFDXhigh red:far-red ratio (R:FR), low PFDXhigh R:FR, or low PFDXlow R:FRlight environments. Leaves that matured under the low PFDXlow R:FR treatment showed a lower percent change in photosynthesis due to Rubisco activation than leaves exposed to the other growth-light treatments. However, there were no significant differences among the growth-light treatments in the maximum contribution of Rubisco activation to the induction response or in the apparent relaxation time for Rubisco deactivation during shade events.