Helmut Metzner

Untersuchungen zur Synchronisierbarkeit einzelner Pigmentmangel-Mutanten von Chlorella

SummaryFour different mutant strains of Chlorella pyrenoidosa were studied under conditions giving rise to synchronized mass cultures. The mutants contained either both chlorophyll a and b, only chlorophyll a or only traces of green pigments.Optimal synchronization was found to occur under a light-dark-regiment of 10:14 hours. It was impossible to achieve a complete synchronization; most of the cells developed autospores only every second cycle. This behavior was independent from the pigmentation of the strain; this was taken as evidence for the assumption, that the chlorophylls are not engaged in the timing process.ZusammenfassungVerschiedene Chlorella-Mutanten, die Chlorophyll a und b (Mutanten 10 und 11), je nach Kulturbedingungen nur Chlorophyll a oder Chlorophyll a und b (Mutante 41) oder nur Spuren von Chlorophyllen (Mutante 31) enthielten, wurden auf ihr Verhalten unter synchronisierenden Kulturbedingungen untersucht.Eine optimale Synchronisation war in einem Licht-Dunkel-Wechsel von 10 Licht- zu 14-Dunkelstunden zu erzielen.Die Synchronisationsschärfe war relativ gering. Unter keiner der angewendeten Kulturbedingungen ließ sich eine Vollsynchronisation erzielen; der Synchronisationstyp war am besten mit einer Gruppen-synchronisation zu vergleichen, bei der laufend Zellen von der einen in die andere Gruppe überwechseln.Unabhängig vom Vorhandensein von Chlorophyll a oder b und vom Ausmaß organischer Zusätze zu den Nährlösungen zeigten alle untersuchten Chlorella-Mutanten den gleichen Synchronisationstyp.Da die untersuchten Mutanten trotz verschiedener Pigmentzusammensetzung bis hin zum praktischen Chlorophyllverlust in gleicher Weise synchronisierbar sind, ist eine Beteiligung der Chlorophylle am “Zeitgeber-Mechanismus” als sehr unwahrscheinlich anzusehen.

Determination of molybdenum in soils and plants using the polarographic adsorptive complex catalytic wave of Mo(VI)-cupferron

Abstract The very sensitive adsorptive complex catalytic wave of Mo(VI)-cupferron with acetic acid-postassium acetate as supporting electrolyte in differential-pulse, normal-pulse direct current and linear-sweep polarographic techniques has been successfully applied to the determination of available molybdenum in soils and molybdenum in plants. Soil and ashed-plant samples are extracted with hot water and the extract solution can be analysed directly without preseparation. The procuedure is very simple and the method is very sensitive for the determination of Mo(VI). The mechanims of the polarographic wave was studied; it behaves as an adsorptive complex and also as an EC (electrode reaction-chemical reaction) parallel catalytic wave.

Water decomposition in photosynthesis? A critical reconsideration

Abstract The results of photosynthesis experiments with 18O labelled water and carbon dioxide are commonly regarded as the strongest arguments for a light-induced water oxidation. In these experiments, however, several sources of error have not been adequately considered. The peculiarities of natural H2OCO2 mixtures and their enzymatically enhanced equilibration are discussed. The unequal distribution of the oxygen isotopes is considered. Relevant data are presented on the CO2 storage in green plant cells and the oxygen burst which is often observed during the beginning of the light period. After the statement of the necessary precautions for isotope experiments data of former measurements of the oxygen isotope discrimination by photosynthetic and respiratory processes are discussed. The data laid down in the literature together with the results of some experiments with deuterated water are taken as disproof of the hypothesis of water oxidation.

Synchronization of Dunaliella cultures

SummaryDunaliella cells exhibit different temperature optima for photosynthesis and cell division. Using this observation a combined light-dark and highlow temperature treatment is given to synchronize cell suspensions.

Isotope ratios in photosynthetic oxygen.

Axenic suspensions of the fresh water green alga Ankistrodesmus braunii were illuminated under aerobic conditions. The released gas mixture was introduced into the ion source of an isotope mass spectrometer, which recorded the 18O/16O ratio. The 18O content of the photosynthetic oxygen (approximately 0.199%) exceeded that of the cell water (approximately 0.197%) significantly.

Massenanzucht phototropher Organismen in einer automatischen Kulturanlage

SummaryA new apparatus is described which permits pure cultivation of 110 l amounts of phototrophic organisms. Some data are given to prove its utility for mass production (kilogram amounts) of algae and photosynthetic bacteria.

Bioelectrochemistry of photosynthesis: A theoretical approach☆

Abstract Green plant cells contain organelles (chloroplasts), which are composed of densely stacked thylakoid membranes. These are covered by a mixture of sensitizers which collect incident photons and direct the excess energy to reaction centers. At these distinctive loci, specially bound chlorophyll molecules donate one of their electrons to acceptor molecules. In contrast to inorganic systems, this charge exchange is strictly directed, by this means creating an electrostatic field between the inside and the outside of the thylakoids. This again represents a form of energy which can be stored until it becomes converted into the chemical energy of ATP molecules. The appropriate treatment of the primary events are discussed. Since the relevant cell structures are of microphysical character, it is unsuitable to describe the light-induced charge exchange reactions in thermodynamic terms. It is recommended that these macrophysical entities be replaced by ionization energies and electron affinities.

Malat-dehydrogenase isoenzymbanden als potentielles chemotaxonomisches kriterium für cyanophyceen-species

Abstract Malate dehydrogenase isoenzymes from eight cyanophycean species were investigated with polyacrylamide disc gel electrophoresis. Using 7% acrylamide the pherograms from each species showed 5–8 zones with malate dehydrogenase activity. It was demonstrated that in Anabaena flos-aquae there are 8 isoenzyme bands which include 3 forms of equal molecular weight, two of which consist of several isomers differing in their net charge. The MDH zymograms of the blue-green algae investigated can be used as “fingerprints”. The isoenzyme pattern of the MDHs of Anacystis nidulans makes its position in the order Chroococcales uncertain.

The electron source in photosynthesis

Abstract The present-day hypothesis of photosynthetic oxygen evolution concerns the release of O2 molecules as the consequence of an oxidative water decomposition. The oxidant, which has to be strong enough to accept electrons from H2O must be produced by a light-driven endergonic redox reaction. Three arguments are usually presented in favor of this assumption; it is, however, demonstrated that they are by no means convincing: First of all it is not justified to compare the oxygen-releasing partial reaction in green plant cells (photoreaction II) with the light-induced electron exchange reaction in photosynthetic bacteria. Secondly, the fact that the HILL reaction of isolated chloroplasts and thylakoids requires the presence of CO2 has been meanwhile well-established. Finally, the published data on mass spectrometric measurements are not valid because the authors did not observe several necessary experimental precautions. This paper presents new data regarding the oxygen and hydrogen isotope effects on primary photosynthetic reactions. The 18O/16O ratio of photosynthetically produced oxygen is definitely higher than that of water. After 16O labelling of applied bicarbonate anions, the 18O content of the released O2 is significantly increased. Preliminary experiments on the photosynthetic oxygen production in deuterated media demonstrated that the reactions which lead to the production of O2 molecules do not discriminate between the two hydrogen isotopes. These observations disagree with the assumption that the released oxygen is the consequence of a H2O oxidation.

Overall kinetics of photosystem II: pH dependence and deuterium isotope effect

Abstract The overall kinetics of photosystem II was scanned by means of a double flash technique. Oxygen evolution by pea thylakoids provided with an artificial electron acceptor was measured under a regime of double flashes of variant intervals. The pH optimum in H2O lies near p1H 7.2 (p1H meaning the pH in H2O), with a first-order rate constant of 800 s−1 at 20°C. In deuterium oxide (D2O), a plateau of maximum reaction rate was found between p2H 6.6 and 7.8 (p2H meaning the “pH” in D2O), the highest rate constant being 550 s−1. The apparent kinetic deuterium isotope effect is therefore 1.45. Outside this plateau region, there seems to exist another isotope effect of 1.2 to 1.3. These effects are small but may nevertheless reflect the fact that more than one step of the photosystem II reaction sequence is involved in the splitting of a bond to hydrogen. However, the effects may also be solvent effects or located on the acceptor side of the photosystem.