Delayed conversion of squalene to sterols during development of Pinus pinea seeds.

During germination of seeds of the gymnosperm, Pinus pinea, radioactivity from [2-14C]-mevalonate proceeded principally through the anaerobic reactions leading to squalene in the first 24 hr in both the haploid endosperm and the diploid embryo, and only with succeeding time (3-9 days) in both cases was label transferred to sterols in oxygen-requiring steps. The rates of turnover must be real and independent in the two tissues, since no consequential interchange of labelled lipids occurred between the endosperm and the embryo. Similar delayed conversion of squalene to sterols has been observed previously during germination of seeds of the angiosperm, Pisum sativum.