Radioimmunoassay of Morphinan Alkaloids in Papaver somniferum Hypocotyls, Callus, and Suspension Cultures

Summary Hypocotyls of poppy ( Papaver somniferum L. cv. Marianne) were assayed for morphinan alkaloid content using a commercially available radioimmunoassay (RIA) for morphine (Abuscreen, Roche Diagnostics). The hypocotyls showed a sharp rise in morphinan alkaloid content on day 3 following sowing, reachin a plateau (9 ng·mg- 1 fresh wt) between day 4 and day 5. Hypocotyl explants were cultured for up to 2 months on solid nutrient medium containing α-naphthaleneacetic acid. During this time and while hypocotyls formed callus, the morphinan alkaloid content fell to a «maintenance» level of 0.4 ng·mg −1 fresh weight in culture. Callus masses retained laticifer-like cells. If cell suspensions were plated with medium lacking growth regulators, plantlets were regenerated and the level of alkaloids found for hypocotyls was re-established. If plated cell suspensions were cultured in the presence of growth regulators, organs formed, but plantlets did not regenerate and the alkaloid content remained at or near the maintenance level. Over a period of a year callus subcultures lost their laticifer-like cells, their embryogenic potential, and their ability to maintain low-level alkaloid production.