State Photosynthesis Research Articles

Wirkung intermittierender Belichtung auf die 14C-markierten Produkte während der Photosynthese-Induktion von Chlorella vulgaris)

Summary CO2 exchange, 14CO2 fixation and radioactive photosynthetic products of Chlorella vulgaris (strain 211-11 f.) were studied during the induction period at + 25° C using intermittent illumination (10 sec light/20 sec dark). The algae were grown under normal air conditions (0,03 vol.-% CO2) at a temperature of +27° C and a light/dark change of 16:8 h. The transients in CO2 uptake in Chlorella measured with an infrared gas analyzer are characterized at +25° C by exhibition of a maximum and a minimum before reaching steady state of photosynthesis. However under condition of intermittent illumination the «primary CO2 uptake« lasted a relatively long time. The autoradiographic studies of the appearance of labelled products during the induction period showed that under intermittent illumination radioactivity was incorporated into malate and aspartate until 1 minute. 3-phosphoglycerate was labelled only after 1 minute and the intermediates of the Calvin cycle after 3 minutes. On the other hand, at normal illumination conditions 3-phosphoglycerate and the sugar phosphates appeared not only earlier, but were also more strongly labelled. The results show that in Chlorella besides the Calvin cycle a carboxylation of phosphoenolpyruvate exists also at higher temperatures. These two carboxylation pathways are involved in the formation of the transients of photosynthetic CO2 uptake in Chlorella. The results are discussed with reference to the preillumination experiments and the C4 pathway in Chlorella.

Excited States and Reactions in Liquids

In the beginning was the three star, one smile of ligh t across the empty face. Dylan Thomas (1) Excited states provide the chemist and biologist alike with suitable scapegoats with which they can at least qualitatively explain unusual data. T he central position occupied by excited states in photosynthesis, vision, laser technology, etc, cannot be denied, while the implication of energetic states in electro and chemiluminescence and oxidation reactions is only just coming to the forefront. From early beginnings, dealing mainly with the long-lived triplet state, it is now possible to observe excited states down to 10-12 sec by utilizing the advances made in technology over the past two decades. The object of this short review is to point out the advances and con­ tributions made by new techniques such as lasers and pulsed accelerators to both the mode of production and the understanding of the nature of excited states. The review will deal mainly with excited states in the liquid phase, with occasional reference to the gas and solid phases when these are ap­ propriate. Several books dealing with various aspects of excited states have been recently published : Theory and Interpretation of Fluorescence and Phos­ phorescence, R. Becker; Excitons in Molecular C rystals, D. P. Craig & S. H. Walmsley; Molecular Spectroscopy of the Tri plet State, S. P. McGlynn, T. Azumi & M. Kinoshita; Photoluminescence, C. A. Parker; the papers of two luminescence conference have also been published: Molecular Luminescence, edited by E. C. Lim; the Proceedings of the International Conference on Luminescence, edited by G. Szigeti; and The Chemistry of Ionisation and Ex­ citation, edited by G. R. A. Johnson & G. Scholes.