The incorporation pattern of 14C amino-acid into protein during the first 8 h of germination in isolated barley embryos (Hordeum vulgare) is described. Two maxima were recognised. The first, at 4 h, was entirely accounted for by scutellum activity and the second, at 8 h, coincided with active radicle elongation. An intervening minimum was situated at 5.5 h. The first peak was insensitive to actinomycin-D but the second showed a partial inhibition by this compound. Only slight changes in enzyme activity were associated with these periods of increased synthesis. Incorporation of 17-14C kaurenoic acid into compounds co-chromatographing with gibberellins was followed over the same period in both embryos and scutella and high activity was found after only 2–4 h. It is concluded that, on the basis of protein synthetic activity, the scutellum is the most probable source of the initial gibberellin stimulu
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