EinleitungIn vor~usgehenden Arbeiten (Lo~z] ~N 1956, 1957; Plxso~ und LoR]~z~ 1958) war eine Methode znr Erzielung ]complett synehroner Chlorella-Kulturen dutch Licht-Dunkel-Weehsel besehrieben und die Beeinflussung des Wachstumsverlaufs synehronisierter Zellen durch Temperatur und Lichtgenui] verfolgt worden. Es wurde nunmehr auf eine genauere Bearbeitung physiologischer Vorgange wahrend der Zellentwicklung (des ,,life cycle") iibergegangen. Die Entwieklung einer Chlorellazelle unseres Stammes ls sich zunachst formal in zwei Absehnitte gliedern (vgl. Abb.
The serotonin content of growing fruits and of germinating seeds of Juglans regia has been studied. In the embryo 0.4-0.6 mg serotonin/g FW were found; in contrast no serotonin was detectable in the fleshy pericarp and in the seed coat. Serotonin was also not detectable in leaves, stems and roots of the adult plant. Most of the serotonin found in the embryo is formed after abscission of the seeds. During the synthesis of serotonin there are no dramatic changes in the chemical composition of the seeds (Tables 3-5).The formation of serotonin could be followed in isolated cotyledons and under sterile conditions. This serotonin formation is stimulated by exogenous tryptophan (Fig. 2). That tryptophan acts as a precursor of serotonin could be demonstrated with labelled DL-tryptophan (benzene ring (14)C) (U). The possibility of stimulating serotonin formation in isolated cotyledons by the addition of tryptophan is limited to a certain stage of development and cannot be observed with material from fully matured seeds (Fig. 3).No serotonin was found in callus tissue and adventitious roots formed by isolated cotyledons; all the serotonin remained in the cotyledons. This was also the case in young seedlings, in which only the cotyledons showed the characteristic high serotonin content, whereas leaves, stems and roots contained no serotonin (Table 6).From these data we conclude that serotonin formation in the embryo of Juglans regia is not a special type of nitrogen storage but a way of ammonia detoxification in which ammonia from protein amino acid degradation is incorporated into serotonin via tryptophan.
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