Carbon Metabolism Responses Associated with Cold Acclimation and Deacclimation of Annual Bluegrass and Creeping Bentgrass.

Annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis stolonifera L.) exhibit differences in their sensitivity to cold deacclimation, which may contribute to interspecific differences in winter injury potential among these two species. The objective of this research was to examine changes in carbon metabolism parameters during cold acclimation and deacclimation, with a focus on canopy photosynthesis and respiration rates, canopy chlorophyll fluorescence, and leaf and crown carbohydrate content. Plants of annual bluegrass and creeping bentgrass were exposed to a cold acclimation period of 2°C for 14 d followed by a sub-zero acclimation period of -2°C for 14 d in a controlled-environment growth chamber.  Following sub-zero acclimation, plants were exposed to temperatures of 8°C for 5 d to simulate deacclimation.  Changes in freezing tolerance (estimated as lethal temperature for 50% kill, LT₅₀) were also assessed following each treatment temperature. Following sub-zero acclimation, creeping bentgrass attained higher freeze tolerance (lower LT₅₀) compared to annual bluegrass.  In general, creeping bentgrass maintained higher canopy photosynthesis rates and carbohydrate accumulation during cold acclimation. In response to deacclimation at 8°C, creeping bentgrass exhibited lower canopy photosynthesis and respiration rates, as well as lower leaf electron transport rates and photochemical yield.