Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/1996
Publication Date: N/A
Interpretive Summary: The opium poppy is grown in many parts of the world. A computer model that can estimate when poppy plants will flower anywhere in the world requires an understanding of how daylength and temperature influence crop development. Many varieties flower quickly in long days but are delayed by cold temperatures. This study was carried out at controlled, near optimum temperatures, to better investigate the effect of daylength on development. Results indicated that the first part of flower development is sensitive to daylength but the period just before flowering is not. However, the daylength during the first part of flower development can affect the length of the latter phase that is insensitive to daylength. Results presented here provide important insights that will make it possible to predict flowering of the poppy crop more accurately anywhere in the world.
Technical Abstract: Photoperiod is a major factor in flower development of the opium poppy (Papaver somniferum L. 'album DC') which is a long day plant. Predicting time to flower in field-grown opium poppy requires knowledge of which stages of growth are sensitive to photoperiod and how the rate of flower development is influenced by photoperiod. The objective of this work was to determine when poppy plants first become sensitive to photoperiod and how long photoperiod continues to influence the time to first flower under consistent temperature conditions. Plants were grown in artificially-lit growth chambers with either a 16-h photoperiod (highly flower inductive) or a 9-h photoperiod (non-inductive). Plants were transferred at 1 to 3-day intervals from a 16- to a 9-h photoperiod and vice versa. All chambers were maintained at a 12-h thermoperiod of 25/20 degrees C. Poppy plants became sensitive to photoperiod four days after emergence and required a minimum of four inductive cycles (short dark periods) before the plant flowered. Additional inductive cycles, up to of a maximum of nine, hastened flowering. After 13 inductive cycles, flowering time was no longer influenced by photoperiod. These results indicate that the interval between emergence and first flower can be divided into four phases: 1) a photoperiod-insensitive juvenile phase (JP); 2) a photoperiod-sensitive inductive phase (PSP); 3) a photoperiod-sensitive post-inductive phase (PSPP); and 4) a photoperiod-insensitive post-inductive phase (PIPP). The minimum durations of these phases for Papaver somniferum 'album DC' under the conditions of our experiment were determined as JP = 4 days, PSP = 4 days, PSPP = 9 days, and PIPP = 14 days.