COLD-ACCLIMATION AND ALTERATIONS IN PROTEIN-SYNTHESIS IN BERMUDAGRASS CROWNS

Cold acclimation (CA) of 'Midiron' and 'Tifgreen' turf bermudagrasses (Cynodon dactylon L. Pers. x C. transvaalensis Burtt-Davy) induced tolerance to lower freezing temperatures and altered protein synthesis in crowns. LT50 (lethal temperature for 50% of plants) values were lowered almost-equal-to 5C after 4 weeks in controlled-environment chambers under CA[8/2C (day/night) cycles with a 10-hour photoperiod] vs. non-CA (28/24C) conditions. LT50 values for 'Midiron' plants decreased from -6.5 to -11.3C after CA and from -3.6 to -8.5C for 'Tifgreen'. Proteins synthesized by isolated crowns were radiolabeled in vivo for 16 hours with S-35-methionine and S-35-cysteine. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography revealed increased synthesis of several cold-regulated (COR) proteins in CA crowns of both cultivars. Synthesis of intermediate molecular weight (MW) (32 to 37 kDa) and low-MW (20 to 26 kDa) COR proteins was greater in 'Midiron' than 'Tifgreen' crowns.