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Summnary. The sites of gibberellin (GA) synthesis in light grown sunflower plants were studied. The results of organ excision and the exogenous application of indole acetic acid and gibberellic acid indicated that gibberellin synthesis occurred in the young leaves of the apical bud. This was substantiated using a combination of diffusion and extraction techniquies. Diffusion of suinflower apical buds on agar for 20 hours revealed a level of gibberellin greater than that obtained by solvent extraction of a similar number of apices, indicating that synthesis of gibberellin was occurring in those apices during the diffusion period. The gibberellin level of apices extracted following a 20 hour diffusion period was the same as that obtained from buds extracted immediately following excision from the plant, again sulggesting that apical buds are sites of gibberellin synthesis. A similar experiment was conducted with young internodal sections, the results indicating that they were not sites of gibberellin synthesis.The ability of various parts of sunflower plants to produce gibberellin as measuired by the agar diffusion technique was correlated to internode elongation, the region of maximum gibberellin production being associated with the region of maximum extension growth.Root tips were also shown to be sites of gibberellin synthesis, this ability beinig confined to the apical 3 to 4 mm region of the root.

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Phenylethylamine (PEA) is an endogenous amine that is structurally and pharmacologically related to amphetamine. Urinary PEA excretion is significantly higher in paranoid chronic schizophrenics than in nonparanoid chronic schizophrenics and normal controls. Diet, hospitalization, and medication do not account for differences in PEA concentrations. These findings offer some indication that PEA may be an endogenous amphetamine.