Temperature Acclimation of Chlorophyll Fluorescence and Carboxylation Capacity From Near‐Instantaneous to Weekly Time Scales

We studied near-instantaneous temperature responses of light-saturated photosynthesis (Asat) 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 Asat 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 Asat and ΦPSII functionally shifted towards the acclimated growth temperatures in both accessions, and both accessions achieved their highest instantaneous maximum values of Asat 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.