TEMPERATURE AND PHOTOPERIOD RESPONSES OF EARLY-MATURING SORGHUM HYBRIDS

This study was designed to assess the response of three early-maturing sorghum (Sorghum bicolor L. Moench) hybrids, Pride P130, X4043, and X3160, to different day and night temperature regimes and photoperiods under controlled environment conditions. Day/night temperatures were 25/20, 30/20, 35/20, 30/15, 30/25 C with a 12-h photoperiod and 30/20 with a 16-h photoperiod. Data on days to bloom, plant height, number of leaves, number of panicles per plant, duration of grain filling, grain weight, shoot weight and harvest index were obtained. Largest grain weights were obtained at 25/20 C. Grain weight, number of panicles, and grain-filling period were reduced markedly by 5 C increments in day temperature. X4043 and X3160 bloomed soonest at 30/20 C. P130 bloomed and matured in fewer days than the other hybrids at all temperatures. The response of the hybrids to a 16-h photoperiod indicated that they all had a long-day type of behavior at the temperature regime tested.