Acclimation of photosynthesis to low temperature in Spinacia oleracea L. I. Effects of acclimation on CO2 assimilation and carbon partitioning

Acclimation of spinach plants grown at 25C to a temperatureof 10C for 10 d resulted in an increased capacity for leafphotosynthesis in saturating light and CO₂ but not at ambientCO₂ concentrations. Gas exchange and chlorophyll fluorescencemeasurements indicated that acclimation was accompanied by anincreased capacity for the regeneration of ribulose-1,5-bisphosphate.Changes in starch, soluble carbohydrates and activities of sucrose-Psynthase and ADP-glucose pyrophosphorylase were measured duringthe acclimation process. There was an initial increase in starchand sucrose during the first 2 d, but these then declined. Therewas an increase in the capacity for sucrose synthesis duringlow temperature acclimation, evidenced by an increase in themaximum activity of sucrose-P synthase activity and an increasein partitioning of ¹⁴CO₂ into sucrose, but there was no increasein the activity of ADP-glucose pyrophosphorylase or carbon partitioninginto starch. Key words: Acclimation, carbon metabolism, gas exchange, low temperature, spinach, Spinacia oleracea