ABSTRACT
Papaver somniferum L. is the most economically important of about 100 species included in the genus Papaver of the Papaveraceae family. Within the genus, the perennial species Papaver bracteatum Lindl. is chief in economic and medicinal importance. Papaver somniferum is considered as a LDP; however, a wide spectrum of photoperiod requirements is found among the various cvs. Based on the climatic conditions, including daylength, for their successful cultivation, different ecotypes have been distinguished among the cultivated lines. In LD-requiring cvs, stem elongation and flower bud initiation are induced in plants with approximately 40 leaves by two long daily photoperiods of 16 hr or by a single continuous light period over 24 hr. Under LD conditions, a higher light intensity accelerates the growth and development of the plants and increases the number of flowers, the size and weight of the capsules, and alkaloid biosynthesis.
