effect of soybean oil and naa on delaying bud break and reducing spring low temperature damage in grape cv. fakhri

delaying bud break, using chemicals is an approach to avoid spring frost damage. therefore, the effect of spraying different concentrations of soybean oil and naphthalene acetic acid (naa) on delaying bud break, altering internal atmosphere and cold hardiness in grape cultivar ‘fakhri’ was studied in 2011 in a commercial vineyard in maryanaj, hamedan using a factorial trial based on randomized complete block design with three replications. selected branches were pruned to six buds. the concentration of carbon dioxide and ethylene gases in the buds were measured three days after spraying. results showed that spraying 10 percent soybean oil alone or in combination with 100 mg/l naphthalene acetic acid caused the highest concentration of carbon dioxide and ethylene in buds, delayed bud bursting for 12 days and improved cold resistance of buds by 5°c. auxin had minor impact on delaying opening and increasing cold tolerance of buds, while five percent soybean oil alone or in combination with naa had intermediate effect. applying oil treatments in march had more considerable effect on delaying bud opening and co2 and ethylene accumulation, compared to april spraying. it seems that applying soybean oil prolongs bud dormancy due to increasing respiratory gases accumulation which subsequently delays bud break and resulted in decreased spring frost damage.