Plant Cell, Tissue and Organ Culture, 8, 103-I11 0987) © Martinus Nijhoff/Dr W. Junk Publishers, Dordrecht - - Printed in the Netherlands Why do lupin cell cultures fail to produce alkaloids in large quantifies? MICHAEL WINK Universit~it Miinchen, Pharmazeutische Biologic, D-80 Miinchen, FRG Key words: alkaloids, cell suspension culture, differentiation, lupins, alkaloid storage, alka- loid transport Abstract. Cell suspension cultures of lupins and other legumesaccumulatealkaloids at levels that are 2 to 3 orders of magnitude lower as compared to the alkaloid concentrations in leaves of the respective differentiated plants. In the plant the alkaloids are formed in leaf chloro- plasts and are then translocated in the phloem sap to the other plant organs, where they are preferentially stored in epidermal tissues. In the cell cultures the formation of specialized storage tissuesis probably repressed.As a consequence the alkaloids formedcannot be stored in large quantities. They are degraded rapidly either in the cellsor in the cellculture medium, which contains a number of hydrolytic and oxidative exoenzymes. Introduction A characteristic feature of higher plants is their capacity to produce a wide variety of metabolites, the so-called secondary compounds. Their com- plete function in plants has been elucidated in relatively few cases so far. But we can ne.vertheless generalize that most of these compounds are important for the fitness of a particular plant species [1-5]. Besides minor roles in the primary metabolism of a plant the secondary compounds usually either serve to attract pollinating or seed-dispersing animals, or, more importantly, to inhibit pathogenic microorganisms (viruses, bac- teria, fungi) or to repel and to deter herbivores (arthropods, vertebrates). As a consequence the structures of secondary metabolites are not strictly at random but structures that have been shaped and optimized during evolution. Having this biological background in mind it is not surprising that we find many active compounds in the plant kingdom which can be exploited as pharmaceuticals, spices, food additives, colours, pesticides or as a library of interesting lead structures, to be further optimized by the synthetic chemist. There are many good arguments why we should try to use plant cell cultures to produce valuable secondary compounds [6-8]. Many laborato- ries worldwide have taken up the opportunity to study whether natural Address for correspondence: Priv.-Doz. Dr. M. Wink, Universitfit Miinchen, Pharmazeut- ische Biologic, Karlstr. 29, D-8000 Miinchen 2, FRG