Beiträge zur Physiologie der Alkaloide1)1) Herrn Prof. K. Mothes aus Anlaß der 70. Wiederkehr seines Geburtstages in Verehrung gewidmet

Summary 1. Discs of the leaf lamina or segments of the leaf petiole of Nicotiana rustica accumulate nicotine from a 10‒3 molar solution reaching an accumulation quotient of about 30. 2. Nicotine-free leaves are obtained from grafts with Lycopersicon esculentum as the stock and Nicotiana rustica as the scion. These leaves do not differ from normal leaves in their velocity and capacity of nicotine uptake. 3. The accumulation of nicotine is higher in the marginal zone of the leaf discs or in the cells near the cut surface of the leaf petioles, as compared with the central zone. 4. The more powerful accumulation in the marginal zone is not caused by a better supply of nicotine from the solution. Higher accumulation in the marginal zone appears likewise if this zone is not in direct contact with the solution. Nicotine is supplied at the opposite side of the discs or the petioles in this experiment and it has to pass the central zone before it can be accumulated in the marginal zone. 5. Respiration inhibitors (Na-azide 10‒3 molar and DNP 10‒4 molar), darkness, and DCMU have no or slight influence on the accumulation and on the development of the accumulating potency in the marginal zone. Inhibition occurs with high concentrations of DNP (10‒3 molar). 6. Salts inhibit the nicotine accumulation, especially in the marginal zone. Alkali-kations (Na+ and K+) and Ca++ act in the same direction but they differ in concentration efficiency. 7. Phosphate buffer inhibits over the whole pH-range tested in accord with the salt effect. Comparing different pH-values, inhibition increases with lower pH. 8. The higher accumulation of nicotine in the marginal zone is not caused by an acidification of the cell sap, leading to an ion trap mechanism. 9. Light- and electronmicroscopic autoradiography show predominant accumulation of applied radioactive nicotine in the cell walls especially in the xylem and in the marginal zone as well as in chloroplasts. Diffuse accumulation in the vacuole is low. 10. In the chloroplasts, vesiculation occurs under the combined action of nicotine and light.