Untersuchungen zur lichtabhängigen Nitritreduktion von Chlorella
Summary1.The dependence of nitrite reduction activity in Chlorella fuscaShihira et Krauss, as measured by uptake of nitrite, on the developmental stage, light intensity and CO2 concentration was investigated.2.There is a quantitative relation between uptake of nitrite-nitrogen and increase of organic cell-nitrogen.3.The kinetics of nitrite reduction in light are linear with time at high CO2 concentrations (3% in air) but biphasic at low CO2 concentrations (0 to 0.03%). In the steady state phase nitrite uptake is stimulated by an increase in the CO2 concentration from 0 to 0.03%. The initial phase and the steady state phase exhibit a different temperature dependence.4.Nitrite uptake in the steady state phase is completely inhibited by iodoacetamide at concentrations which inhibit the photosynthetic CO2 reduction (5×10−5 M). At lower iodoacetamide concentrations (1 to 2×10−5 M) the linear time course of nitrite uptake at high CO2 concentrations is changed in the same manner as it is when the CO2 concentration is lowered.It is concluded that under special conditions (e.g. low CO2 concentration) the rate of steady state nitrite reduction in light is limited by the supply of carbon skeleton (i.e. N acceptors in the synthesis of organic nitrogen compounds) from the photosynthetic CO2 reduction cycle.5.Pre-illumination in the presence of nitrite followed by a dark period depresses the initial phase of nitrite uptake in light at low CO2 concentrations. Pretreatment with nitrite in the dark lowers the nitrite uptake of the cells in the initial phase by exactly the same amount of nitrite which has been taken up during the pre-darkening period.
 It is concluded that there is a correlation between the initial phase of nitrite reduction in light and the respiration-linked nitrite reduction in the dark.
Stickstoffbilanz und Stickstoffverlust
Zusammenfassung1.Abgeschnittene Blätter, welche mit den Stielen oder der Blattbasis im Wasser stehen, geben nur geringe, bilanzmäßig unbedeutende Stickstoffmengen an die Flüssigkeit ab.2.N-Defizite in höheren und niederen Pflanzen beruhen, sofern das Entweichen von gasförmigem, gebundenen Stickstoff (NH3, Stickoxyde) verhindert wird, auf der Entbindung von molekularem Stickstoff.3.Diese Reaktion setzt voraus: Nitrit, aminischen Stickstoff und eine hohe Azidität. Sie erfolgt nach dem Schema HNO2+RNH2=N2+ROH+H2O.4.Im Zuge der Nitratreduktion spielt bei gesunden höheren Pflanzen diese N2-Entbindung keine erhebliche Rolle, da offenbar die Nitritstufe zu schnell durchschritten wird.5.In Preßsäften und in Pilzkulturen führt Nitratgabe jedoch zu erheblichen N-Verlusten, ein indirekter Beweis der intermediären Bildung von Nitrit.6.Bei Hefe deutet die Rolle von Sulfhydrilkörpern darauf hin, daß diese die Nitratreduktion fördern können.7.Eine Entbindung von Stickstoff auf Kosten von reduziertem Stickstoff war nie zu beobachten. Die Rolle der nitrifizierenden Bakterien ist vorerst einzigartig.8.So unökonomisch die N2-Entbindung auch erscheint, kann sie im Leben der Pflanze doch eine Bedeutung gewinnen durch das Entfernen von Nitrit, einem starken Zellgift. DieEntbindung wird somit zu einer Entgiftungsreaktion.
Geologic proof on paleo-glaciation remains in Laoshan Mountain
Laoshan Mountain is the highest mountain in China coast.Various typical geomorphic features of glarosion,glacial deposition,rare glacial moraine coast and glacial moraine fans in east are well developed in Laoshan Mountain.Well preserved four glacial epochs are identified in Laoshan Mountain.In early Pleistocene,the altitude of snowline ranged from 60 m to 90 m in east.More than sixty paleo-glacial tongues were developed in Laoshan Mountain,some of them which located in east extended into the Yellow Sea.Sporopollen analysis indicates that the climate in Laoshan Mountain is very cold during the ice age.Multi-modal grain-size probability curves of the moraines are the typical characteristics of sediments deposited by glaciation.Regional landforms and climatic conditions are the key factors dominating the altitude of snowline during the ice age.