Temperature Acclimation of Chlorophyll Fluorescence and Carboxylation Capacity From Near-Instantaneous to Weekly Time...

We studied near-instantaneous temperature responses of light-saturated photosynthesis (A_sat) and the operating efficiency of photosystem II (ΦPSII) in relation to acclimation of photosynthetic biochemistry to temperature at the timescale of 1-8 days. We grew two closely related Brassica oleracea L. accessions under diurnal temperature ranges of 15°C-25°C and 5°C-15°C, representing the warm and cool native environments of the two accessions. Near-instantaneous temperature responses of A_sat and ΦPSII were measured on acclimated plants exposed to a temperature ramp from 10°C to 45°C. Biochemical acclimation was quantified by switching plants between warm and cool regimes before measuring photosynthetic variables at Day 1 and Day 8 after the switch. Near-instantaneous temperature optima of A_sat and ΦPSII functionally shifted towards the acclimated growth temperatures in both accessions, and both accessions achieved their highest instantaneous maximum values of A_sat and ΦPSII when grown under representative native regimes. Differences in maximum carboxylation capacity were evident by Day 1; no further change was detected by Day 8. Our results highlight functional coordination between adaptation, acclimation and near-instantaneous temperature responses of photochemistry and biochemistry. Moreover, our results suggest photosynthetic biochemistry can acclimate to temperature changes within a day.