Weitere Untersuchungen zum Problem der Kernaktivität bei gesenktem Zellstoffwechsel

Abstract

1. Nucleated, 1 cm long parts of the uninucleate green algaAcetabularia mediterranea form caps with shorter stalk lengths than do cells growing up from zygotes. This is due to the fact that these parts possess a maximum sized nucleus, which, as to the production of “morphogenetic” substances, has a higher activity than a small nucleus. 2. If nucleated, 1 cm long parts are darkened for 14 days and then re-illuminated, cap formation happens at still shorter stalk lengths. This confirms that even if photosynthesis is suspended, the nucleus remains active and continues to release precursors of the morphogenetic substances or of a nuclear product leading to the synthesis of these substances within the cytoplasm (see the preceding paper). 3. After treatment with Trypaflavin, the stalk is still more shortened. This means that the nucleus remains more active in Trypaflavin than in darkness. This finding is in agreement with the fact, that the size of the nucleus and nucleoli is reduced in darkness, but not in Trypaflavin. Probably in Trypaflavin the primary nuclear product released into the cytoplasm continues to be synthesized within the nucleus. 4. In Dinitrophenol the building up of a store of morphogenetic substances cannot be observed. Thus more of the stalk must grow out before a cap is formed. This is apparently due to the strong effect of Dinitrophenol on energy metabolism. 5. Cap formation takes place, if there is a sufficient level of active morphogenetic substances, but it is in wide limits independent of the mass of proteins and chloroplasts.