Abstract
To clarify the heading behavior of the thermo-sensitive sorghum varieties, effects of the timing and duration of the night temperature treatments on the panicle initiation and the final leaf number were examined. Two hybrid cultivars (FS403 and GROWERES30F) and one inbred (932233B) strain were grown in pots under controlled climatic conditions both in low night temperature (LT:15℃) and high night temperature (HT: 30℃). Plants were tramsferred from LT to HT or from HT to LT with several combinations of the timing and duration of temperature treatments. LT induced panicle initiation and reduced final leaf number and HT restrained panicle initiationand increased final leaf number in all varieties. The time when plants first became sensitive to low night temperature was earlier in 932233B than in FS403 and GROWERES30F. The minimum LT duration requiredto induce the panicle initiation (MDPI) was the shortest in 932233B and the longest in GROWERES30F. MDPI was, however, decreased with growth progress in all varieties. The time when plants first became sensitive to high night temperature was the earliest in 932233B and the latest in GROWERES30F.
