Cold acclimation inhibits CO₂-dependent stimulation of photosynthesis in spring wheat and spring rye

Abstract

We assessed the effects of short-term elevated CO 2 on the light-saturated rates of photosynthesis (A sat ) of spring (‘SR4A’, ‘Katepwa’) and winter (‘Musketeer’, ‘Norstar’) wheat ( Triticum aestivum L.) and rye ( Secale cereale L.) cultivars grown at ambient CO 2 (380 µmol C·mol –1 ) at either 20/16 °C (nonacclimated, NA) or 5/5 °C (cold acclimated, CA). In spring wheat–rye, cold acclimation decreased CO 2 -stimulation of A sat by 45%–60% relative to NA controls following a short-term (80 h) shift of plants from ambient to elevated CO 2 (700 µmol C·mol –1 ). In contrast, in winter wheat–rye, cold acclimation enhanced CO 2 -stimulation of A sat by 15%–35% relative to NA controls upon a shift to elevated CO 2 . The stimulation observed for CA spring cultivars was about 60% less than that of CA winter cultivars. We conclude that a short-term exposure of spring cultivars to elevated CO 2 cannot compensate for the cold acclimation-induced inhibition of A sat . Cold acclimation of spring cultivars appeared to exacerbate Rubisco CO 2 substrate limitations present under ambient CO 2 . Furthermore, CA spring cultivars were unable to adjust their short-term temperature sensitivity of A sat under elevated CO 2 compared with the winter cultivars.