METHOD: Light Stress CONDITIONS: Lab - 18h light at 70% RH METHOD NARR: A 2-compartment chamber for exposure of previously frozen leaf disks to high-light intensity at low temperature was constructed. A single plant of cmm was p temp was above freezing, and left out overnight with freezing temps and allowed to thaw the next morning. Tissue temp, light energy levels and air temp were measured. Freeze-Thaw treatments were conducted on acl in the labe. Post-thaw light stress was measured in acl through photosynthesis and respiration. RESULTS NARR: Irreversible damage was usually indicated when ion leakage >30% of total ions present in cell. The sharp increase in ion leuggests the difference between cell survival and death. While the various freezing stresses and post-thaw treatments had no effect on chlorophyll content of tissue from acl, photosynthetic function was consistently and markedly more dce of light than in the paired dark-held tissues. Light-limited and light-saturated photosynthesis were both eliminated at -5C. The effects on respiration were limited. AUTHOR EXPLANATION: Photosynthesis was the mostfreezing stress, followed by ion leakage and then respiration. The results presented may help explain why freezing injury is not always immediately apparent. If freezing tolerance and tolerance of light stress are ince in the absence of light may lead to erroneaous conclusions about the relative frost-tolerance of plant materials.