METHOD: Physical Measurement METHOD NARR: All plants were grown initially at 20/16C day/night temperature with 8h daylength and a photosynthetic photon flux density of 150 umol m-2 s-1. After 4 weeks, some of the plants were harve transferred to 12/9C or 5/2C temperature regimes with the other parameters stying the same. Plants were grown at these temperatures long enough to harvest leaflets that had developed fully under these conditions. Physicalmeasured, along with oxygen evolution and dark respiration. RESULTS NARR: It is possible to detect the primary injury of photoinhibition in cmm at temps as high as 12C. Much of the increase in leaf thickness was due to the iade layer. There were no significant differences in light saturated CO2-saturated O2 evolution or in dark respiration. AUTHOR EXPLANATION: Data suggest that there were an increased number of damaged PSII centers in the cold-acclimaes on the reducing side of QA may be sensitive to growth temperature. Leaves developed at chilling temperatures have a reduced capacity to utilize available light energy. Cmm is unable to alter its susceptibility to photon at 12/9C and 5/2C. These results support the idea that cmm exhibits properties that are typically associated with chilling sensitive rather than freezing tolerant plant species.