Der Einflu? der H?henlage auf Ei- und Gelegegr??e bei Kohlmeisen (Parus major)

In 7 Untersuchungsgebieten ließ sich ein signifikanter Anstieg im Eivolumen mit zunehmender Höhe nachweisen (Tab. 1). Hingegen wurde die geringste Gelegegröße in einem isolierten Stadtbiotop ermittelt; eine Zu- oder Abnahme der Gelegegröße in Abhängigkeit von der Höhe der Untersuchungsgebiete konnte nicht festgestellt werden (Tab. 2). Der Bruterfolg war im Stadtbiotop (100 m) und im höchstgelegenen Gebiet (875 m) im Vergleich zu Laubund Nadelwäldern in 300 m Höhe sehr niedrig (Tab. 3). Lediglich in der isolierten Stadtpopulation ließ sich eine reduzierte Gelegegröße als Anpassung an die sehr ungünstigen Ernährungsbedingungen erkennen. In der Höhe wird offenbar durch den ständigen Zustrom aus Tallagen eine Anpassung der Gelegegröße an die Höhenbedingungen verhindert. Als Anpassung an die klimatisch schwierigen Bedingungen in größeren Höhen ist die Zunahme der Eigröße mit der Höhe zu werten. Wegen des hohen Genflusses ist diese Anpassung vermutlich nicht genetisch fixiert.Egg size increased significantly from lowland urban habitats (Frankfurt, Hessia, West Germany) to coniferous mountain habitats (Garmisch-Partenkirchen, Bavaria). Clutch size was lowest in urban parks and cemeteries but did not increase or decrease with altitude (Tab. 2). Breeding success was extremely low in urban and mountain habitats compared to deciduous woods in 300 m (Tab. 3). In isolated urban parks a reduction in clutch-size indicates adaptation to poor feeding conditions. The mountain populations are not isolated from lowland ones. Therefore we conclude that perpetual influx of genes from other than mountain populations prevents selection producing a suitable clutch-size. Egg-size on the other hand is well adapted to altitude. Young hatched from large eggs are able to cope better with unfavourable weather conditions regulary met in mountain areas. Because geneflux is high, in mountain populations adaptations in egg-size are unlikely to be fixed genetically.     

An Inwardly Rectifying Cation Current across the Plasma Membrane of the Green Alga Eremosphaera viridis

Ion currents across the plasma membrane of the unicellular greenalga Eremosphaera viridis were characterized with electrophysiologicalmethods, especially the two electrode voltage-clamp-technique.Under different conditions, at increased external Cl^–concentrations or after perfusion of different anion channelblockers (A9C (anthracen-9-carboxylic acid), NPPB ((5-nitro-2-3-phenylpropylamino)benzoic acid) and ZnCl₂), increased instantaneous negative currentswere observed. The negative currents were carried by cationfluxes into the cell. The transporter responsible had low selectivityamong potassium and sodium. Additionally also divalent cationswere transported. The cation influx was not affected by thepotassium channel inhibitors TEA (tetraethylammoniumsulfate),Ba²⁺ or Cs⁺ at concentrations of 1 mM, but was strongly reducedby 100 µM AlCl₃. Our results with E. viridis demonstrate,for the first time for an unicellular alga, the existence ofan inwardly rectifying cation current across the plasma membrane.Parallels and differences to inwardly rectifying cation currentsand channels described in plasma membranes of other plant cellsare discussed. (Received May 10, 1993; Accepted September 13, 1993)     

Der Einfluß von Natrium- und Kalium-Ionen auf die Photophosphorylierung bei Ankistrodesmus braunii

Summary During short-time experiments (30 sec to 60 min) sodium ions stimulate the phosphate uptake and especially the ³²P-labelling of the organic TCA-soluble phosphate compounds up to 1,500% (K⁺=100%). The labelling is maximally stimulated in the light and in the dark at concentrations of about 5×10^-3 mol/l Na⁺ and at pH 8. Lithium ions stimulate ³²P-labelling in a similar but less effective way. In comparison, in the presence of potassium ions the ³²P-label decreases.It was investigated whether sodium ions specifically stimulate the ATP-synthesis or some reaction of the photosynthetic carbon reduction cycle or whether they only enhance the ³²P-labelling of phosphorylated compounds.Separation by thin-layer chromatography of the MCF-soluble phosphate fraction showed that labelling of all compounds investigated was stimulated by Na⁺ to a similar extent.Experiments performed in red and far-red light (683 and 712 nm) under nitrogen and in the presence of various DCMU-concentrations, as well as in the presence of antimycin A and CCCP showed that Na⁺ exerts no specific influence either on the cyclic or on the non-cyclic photophosphorylation in vivo.ATP-dependent reactions such as ¹⁴CO₂-fixation or glucose uptake are not influenced by Na⁺.Since Na⁺ does not change the size of phosphate pools in a different way from K⁺, there is no evidence for the assumption that the Na⁺-dependent increase in the ³²P-labelling is due to its action on the chloroplast membrane in increasing its permeability to orthophosphate ions. This is supported by the lack of any effect of sodium plus phosphate ions on the CO₂-fixation.Therefore the results give no evidence that sodium acts directly on phosphorus metabolism inside the cell. It is suggested that its action is localised at the phosphate-transporting site of the plasmalemma.     

Der Einfluß von Natrium- und Kaliumionen auf die Phosphataufnahme bei Ankistrodesmus braunii

Summary The uptake of phosphate as influenced by sodium and potassium ions was investigated in the light and in the dark. It was found to be a function of the external phosphate concentration. At a low concentration (up to 10^–5 mol/l) in the presence of Na⁺ phosphate is quickly absorbed and hence phosphate is the limiting factor for further labelling. In the presence of K⁺ phosphate uptake is constant over a long period.The enhancement of phosphate uptake by Na⁺ is also found when the external concentration of P is raised up to 10^–4 mol/l. Then the gross uptake proceeds over six hours, with the greatest Na⁺-dependent increase occurring in the label of the TCA-insoluble phosphate fraction (P_u).The phosphate uptake is strongly dependent on the pH of the reaction mixture. In the presence of Na⁺ it is highest between pH 5.6 and 7. As the uptake in the presence of K⁺ parallels the dissociation curve of the dihydrogen form H₂PO ₄ ^– , the Na⁺-enhancement is optimal in the alkaline pH range (pH 8).On the basis of a comparison between the pH-dependence of phosphate uptake and the dependence of the uptake on the external phosphate concentration analysed by a method of enzyme kinetics, it is suggested that Ankistrodesmus metabolically transports H₂PO ₄ ^– but not HPO ₄ ⁼ . Moreover, it is concluded from the absence of light stimulation and the weak inhibition of the uptake by DCMU or CCCP in the presence of K⁺ that at low P-concentrations the diffusion is limiting the uptake. Only at higher concentrations is an active phosphate uptake measured.Furthermore it is concluded that the observed Na⁺-stimulation of the ³²P-labelling of the TCA-soluble and insoluble compounds inside the cell is indirect and depends only on the action of Na⁺ and K⁺ ions at the first transport site in the plasmalemma.     

Veränderungen der Phosphatfraktionen,besonders des Polyphosphates,bei synchronisierten Ankistrodesmus braunii-Kulturen

Zusammenfassung Ankistrodesmus braunii wurde in phosphathaltigem (5 · 10^-3 mol PO ₄ ^--- /l) und in Phosphatmangel-Nährmedium (ca. 1 · 10^-7 mol PO ₄ ^--- /l synchron kultiviert (14 Std Licht zu 10 Std Dunkel). Durch fraktionierte Extraktion wurden die pool-Änderungen der verschiedenen Phosphatfraktionen, besonders die des Polyphosphats während des Lebenscyclus der Algen bei + und-P-Kulturen gemessen. Während der Lichtphase findet bei den +P-Kulturen eine beträchtliche Erhöhung des Gesamtphosphates statt, die im Dunkeln fehlt. Bei fast konstantem niedrigem Orthophosphat-pool zeigte sich eine Zunahme des Po, und ein besonders starker Anstieg der Polyphosphat- und Nucleinsäurephosphatfraktion. Im Laufe des Synchroncyclus finden charakteristische erhebliche Schwankungen im prozentualen Anteil der verschiedenen Phosphatfraktionen statt, die bei + und-P-Kulturen weitgehend gleich verlaufen. Besonders auffällig ist der inverse Verlauf des Polyphosphates gegenüber dem Nucleinsäurephosphat während der späten Licht- und der gesamten Dunkelphase. Die Polyphosphate sind demnach in starkem Umfang am Phosphatstoffwechsel beteiligt. In der Diskussion werden die Veränderungen der Phosphatfraktionen mit den verschiedenen Entwicklungsphasen der Algen während des Synchroncyclus in Beziehung gesetzt.

---

Changes in phosphate fractions, especially the polyphosphates, in synchronously growing cultures of Ankistrodesmus braunii

Summary The unicellular alga Ankistrodesmus braunii was grown by synchronous culture method in a phosphate containing medium of 5 · 10^-3 M PO₄ and in a phosphate deficient medium of about 1 · 10^-7 M PO₄ · (14^h light to 10^h darkness).The pool changes of the various phosphate fractions, especially of the polyphosphates, during the life cycle of the algae, cultured in plus or minus phosphate containing medium, were determined by fractionating extraction.Contrary to darkness, during the light phase an exceptional increase in the total phosphate is observed.While the orthophosphate pool remains at an almost constant level, an increase is seen in the Po, and an significantly stronger increase occurs in the polyphosphate and nucleic acid phosphate fraction. During the synchronous life cycle of the algae characteristic changes occur in the percentage of the various phosphate fraction. These changes are the same in plus und minus P-cultures.The diverse course of the polyphosphate as compared with the nucleic acid phosphate during the late light phase and the entire dark phase is significant.It follows therefore that the polyphosphates are strongly involved in the phosphate metabolism of the algae.In the discussion, correlations of the changes in the phosphate fractions with the various developmental stages of the alga during its synchronous life cycle were tentatively made.

---

Abkürzungen TCE Trichloressigsäure - P Phosphat - Pa Orthophosphat - Po Organisches säurelösliches Phosphat - Pp Polyphosphat - NS-P Nucleinsäurephosphat