Phases of Flower Development in Opium Poppy under Various Temperatures

Abstract

Flower development in opium poppy (Papaver somniferum L.) has been divided into four phases from emergence to anthesis, which mark changes in its sensitivity to photoperiod: a photoperiod-insensitive juvenile phase (JP), a photoperiod-sensitive inductive phase (PSP), a photoperiod-sensitive post-inductive phase (PSPP), and a photoperiod-insensitive post-inductive phase (PIPP). To predict flowering time under field conditions, it is essential to know how these phases are affected by temperature. Plants were grown in artificially lit growth chambers and received three temperature treatments: 15/10, 20/15, and 25/20°C in a 12-hr thermoperiod. Plants were transferred within each temperature regime from a non-inductive 9-hr to an inductive 16-h photoperiod or vice versa at 1- to 4-day intervals to determine the durations of the four phases. Temperature did not affect the durations of the first two phases (i.e., JP lasted 3 to 4 days and PSP required 4 to 5 days). The most significant effect of temperature was on the duration of PSPP, which lasted 28, 20, and 17 days at 15/10, 20/15, and 25/20°C, respectively. The temperature effect on PIPP was small (maximum difference of 3 days for treatments) and the data too variable to indicate a significant trend. Our results indicate that PSPP is the only phase that clearly exhibits sensitivity to temperature.