Steroidal saponins in etiolated,greening and green leaves and in isolated etioplasts and chloroplasts ofAvena sativa

Summary New results obtained in course of studies on steroidal saponins of oat indicate that in contrast to our former conclusions the prolamellar body (PLB) is not built up by steroidal saponins. Saponin content of whole leaves is similar in green as well as in etiolated leaves and does not change significantly during development of leaves. In contrast to chloroplast, isolated purified etioplasts contain high amounts of the desgluco-avenacosides, which were thought to be responsible for the tubular structure of PLBs. The amount of these PLB-saponins, however, is 10–60 times higher in isolated etioplasts than in etiolated leaves. Evidence is presented that the PLB-saponins originate from leaf-saponins during disruption of cells and attach to etioplasts or PLBs. This attachment to PLB-components explains our former results that the PLB-destruction during greening is accompanied by a decline in the amount of the desgluco-avenacosides in isolated PLB-fractions of greening leaves.