Phases of Development to Flowering in Opium Poppy (Papaver somniferumL.) under Various Temperatures

Abstract

Development up to flowering in opium poppy (Papaver somniferumL.) 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 different temperature treatments: 15/10, 20/15 and 25/20 °C in a 12 h thermoperiod. Plants were transferred within each temperature regime from a non-inductive 9 h to an inductive 16 h photoperiod orvice versaat 1–4 d intervals to determine the durations of the four phases. Temperature did not affect the duration of the first two phases (i.e. JP lasted 3–4 d and PSP required 4–5 d). The most significant effect of temperature was on the duration of PSPP which was 28, 20 and 17 d at 15/10, 20/15 and 25/20 °C, respectively. The temperature effect on PIPP was small (maximum difference of 3 d between 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.