Variations in Flowering, Vegetative Growth, and Dry Matter Partitioning Induced by Photoperiod and Temperature Treatments in Papaver somniferum

Estimating yields of illicit narcotic crops requires knowledge of how climate, soil, and geography affect these crops. One method for estimating yields is to create databases from which to develop simulation models. This experiment is part of one of those databases, designed to determine if flowering time can be affected in young poppy seedlings by manipulating photoperiod (PP) and temperature. Plants were grown in chambers under a 12-, 13-, 14-, or 24-h PP and a 12-h thermoperiod of 25/20C. Plants at 10 or 20 days after emergence were transferred to separate chambers and treated for 48 h with either a) 10C and a 12-h PP or b) a 24-h PP and a 12-h thermoperiod of 25/20C. Days to flowering (DTF) decreased with increased PP, especially between 12 and 13 h. The 48-h PP interruption decreased DTF for PPs <24 h for both seedling ages, the effect being more pronounced for 10 d and for the 12-h PP. The 48-h 10C interruption had no effect on DTF. The poppy capsule, from which the gum is harvested, was a larger proportion of the shoot biomass under PPs >14 h, but capsule biomass was a positive linear function of DTF. DTF depends on PP and biomass at flowering depends on DTF.