The Influence of Inhibitors of Chloroplast Differentiation on Chlorophyll and Cardenolide Accumulation in Somatic Embryos of Digitalis lanata

Abstract

Low concentrations of chloramphenicol (10 −8 and 10 −7 mol 1 −1 ) and of 3-aminotriazol (10 −6 and 10 −5 mol 1 −1 ) reduced the accumulation of cardenolides in illuminated somatic embryos (stage-II-globules and late embryo structures) of D. lanata more than that of chlorophylls. In contrast norflurazon (10 −6 and 10 −5 mol 1- −1 ) repressed chlorophyll synthesis completely whereas cardenolide accumulation reached still about 20% of the control level. These results indicated that there is no direct relation between chlorophyll and cardenolide accumulation. Electron micrographs showed that the administration of 10 −7 mol norflurazon 1 −1 caused the formation of abnormal plastids which contained only rudiments of the inner membranes characteristic for chloroplasts. The formation of these membranes therefore seems to be no prerequisite for the biosynthesis and accumulation of cardenolides.