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Effects of various combinations of day/night temperature regimes on growth and flag leaf occurrence in Dendrobium nobile Lindle, ´Yukidaruma, King´, ´Malones, Fantasy´, ´Golden Blossom, Kogane´ and ´Snowflake, Red star´ were investigated under controlled environment chambers. Plants were grown under 7 different day/night temperature environments (combinations of 15, 20, 25, 30℃ night temperature with 30C day temperature and vice versa) with 250±50 μ㏖·m^(-2)·s^(-1) natural light for 9 hr photoperiod. Stem length during early period was affected by rather average daily temperature (ADT) than difference between day and night temperature (DIF). Growth rate of stem length became higher as ADT increased. However, final stem length was definitely affected by DIF in which stem length increased as +DIF increased. These responses to temperature differed among cultivars. For instance, ´Yukidaruma, King´, ´Malones, Fantasy´, and ´Golden Blossom, Kogane´ showed similar patterns with respect to DIF as described above, whereas ´Snowflake, Red star´ was not influenced by both ADT and DIF. Stem diameter in all cultivars was more influenced by day temperature than DIF or .ADT in which the biggest stem diameter was obtained from a little +DIF condition with high day temperature. Node numbers of 3 cultivars (´Yukidaruma, King´, ´Malones, Fantasy´ and ´Golden Blossom, Kogane´) increased as DIF increased positively. However, ´Snowflake, Red star´ was not influenced by growth temperature in node number. Leaf number also showed a similar pattern with the node number. The day of flag leaf occurrence was influenced by ADT in all cultivars used in this study. Flag leaf occurred earlier as ADT increased. In the same ADT, flag leaf tended to occur earlier in -DIF thane in +DIF. For instance, flag leaf of ´Snowflake, Red Star´ occurred 20 days earlier in -DIF (15/30) than in +DIF (30/15).
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