Development Rate during Four Phases of Chrysanthemum Growth as Determined by Preceding and Prevailing Temperatures

Abstract

Abstract Time required to complete four developmental phases in chrysanthemum ‘Bright Golden Anne’ (Dendranthema grandiflora Tzvelev.) was determined under greenhouse conditions at constant temperature setpoints of 10, 15, 20, 25, 30, or 20 day/16C night. The four developmental phases were: I—start of short days to visible bud (2-mm-diameter terminal flower bud), II—visible bud to disbud (10-mm-diameter terminal flower bud), III—disbud to color (flower bud showing first color), and IV—color to flower. Plants either remained at the same temperature during all four phases or were moved to one other constant temperature regime after phase I, II, or III. Fastest development during all phases occurred at 20 day/16C night or constant 20C. Temperature of previous phases had less of an effect on future phases as plant development progressed. Low temperature (10C) during phase I delayed development in phase II, and high temperature (30C) during phase I and II delayed development during phase III. The length of each phase could be predicted based on the temperature preceding and during the phase. Optimum temperatures for fastest development during the four phases were calculated as 21.3, 20.3, 23.1, and 19.1C, respectively.