TY - JOUR T1 - Applying Chlorophyll Fluorescence Technique to Cold Hardiness Studies of Grapevines JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 210 LP - 217 DO - 10.5344/ajev.2002.53.3.210 VL - 53 IS - 3 AU - Hongying Jiang AU - G. Stanley Howell Y1 - 2002/01/01 UR - http://www.ajevonline.org/content/53/3/210.abstract N2 - Woody tissue cold hardiness and chlorophyll fluorescence of Concord (Vitis labruscana Bailey) grapevines were measured regularly during the dormant seasons in 1997 to 1998, 1998 to 1999, and late winter 2000. Chlorophyll fluorescence was measured after a controlled freeze-stress. Fv/Fm was used as an indicator of viability. Response magnitude varied with each portion of the dormant season and the type of woody tissues. Fv/Fm temperature inflection points (temperature at which no and 100% tissue injury occurred) were closely related with T50 (temperature at which 50% of the sample was injured) calculated from a regrowth test. Injury thresholds Fv/Fm50 , Fv/Fm50 , and Fv/Fm100 (the Fv/Fm values when no, 50%, and 100% of the tissue were injured, respectively) are proposed for different woody tissues at three periods of the dormant season. Preliminary application of two fluorometers and field measurement was also demonstrated.Acknowledgments: The authors gratefully acknowledge the technical assistance of J.A. Flore, F.W. Ewers, B. Rowe, J. Dwyer, S. Breitkreutz, L. Blain, M. C. Vasconcelos, Jun Song, and W. Nail and the statistical assistance of O. Schabenberger. ER -