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

Development up to flowering in opium poppy (Papaver somniferumL.)has been divided into four phases from emergence to anthesiswhich mark changes in its sensitivity to photoperiod: a photoperiod-insensitivejuvenile phase (JP), a photoperiod-sensitive inductive phase(PSP), a photoperiod-sensitive post-inductive phase (PSPP) anda photoperiod-insensitive post-inductive phase (PIPP). To predictflowering time under field conditions, it is essential to knowhow these phases are affected by temperature. Plants were grownin artificially-lit growth chambers and received three differenttemperature treatments: 15/10, 20/15 and 25/20 °C in a 12h thermoperiod. Plants were transferred within each temperatureregime from a non-inductive 9 h to an inductive 16 h photoperiodorvice versaat 1–4 d intervals to determine the durationsof the four phases. Temperature did not affect the durationof the first two phases (i.e. JP lasted 3–4 d and PSPrequired 4–5 d). The most significant effect of temperaturewas on the duration of PSPP which was 28, 20 and 17 d at 15/10,20/15 and 25/20 °C, respectively. The temperature effecton PIPP was small (maximum difference of 3 d between treatments)and the data too variable to indicate a significant trend. Ourresults indicate that PSPP is the only phase that clearly exhibitssensitivity to temperature. Days to flower; opium poppy; Papaver somniferumL.; phases of flower development; photoperiod; temperature