Effects of temperature and CO₂ on the relationship between Rubisco activation and electron-transport activity in rice

Abstract

We examined the effects of temperature and [CO₂] on Rubisco activation, ΦPSI, ΦPSII, and NPQ in rice including the transgenic plants with increased or decreased Rubisco. The Rubisco activation was higher at low temperature, declined with increasing temperature, and decreased to 60% above 42˚C. TheΦPSI/ΦPSII and NPQ were also higher at low temperature, and declined with temperature. NPQ increased again above 42˚C. The Rubisco activation was higher at low [CO₂] and declined at elevated [CO₂]. The ΦPSI/ ΦPSII and NPQ were also higher at low [CO₂] and declined with elevating [CO₂]. Whereas rbcS-antisense rice showed a high activation of Rubisco and high ΦPSI/ΦPSII and NPQ, rbcS-sense rice had a lower activation of Rubisco. Thus, under the conditions of low temperature, low [CO₂] and low Rubisco contents, high activation state of Rubisco is always associated with high ΔpH generated from the cyclic electron flow around PSI.