Chlorophyll Catalysis and Einstein's Law of Photochemical Equivalence in Photosynthesis

Warbürg, Otto; Krippahl, Gujnter; Lehman, A. J.

doi:10.1002/j.1537-2197.1969.tb09747.x

Cited by 15 publications

(6 citation statements)

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“…Accompanying this restrictive doctrine which fostered purely theoretical and speculative characterizations of photosynthetic mechanisms were other erroneous beliefs shared by some of the most eminent contemporary authorities in the field, e.g. : (i) the function of light is the 'photodecomposition of CO2' (Warburg et al 1969) (ii) 'the chloroplast is only an incomplete machine (that can).., evolve 02 from H20 in the light (but is) deficient in the enzymatic mechanisms operative in the various steps by which CO2 is converted into the normal assimilation product' (Van Niel 1956), and (iii) 'if phosphorylation does play an auxiliary role in photosynthesis -which is by no means certain -we think it much more probable that the required highenergy phosphates are supplied by nonphotochemical oxidation processes than that light quanta are diverted for their synthesis' (Rabinowitch 1945).…”

Section: Introductionmentioning

confidence: 99%

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Arnon

1995

Photosynth Res

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The aim of this article is to assemble and integrate, from a personal perspective of a research participant, seldom examined evidence that is incompatible with some basic tenets of photosynthetic electron transport, the cornerstone of which is the Z scheme. The nonconforming evidence pertaining to the mode of ferredoxin reduction and the role of the copper redox protein, plastocyanin, indicates that contrary to the Z scheme ferredoxin is reduced in two experimentally distinguishable ways: oxygenically by PS II (renamed the oxygenic photosystem), without the participation of PS I, and anoxygenically by PS I (renamed the anoxygenic photosystem). It also indicates that plastocyanin is not only, as the Z scheme asserts, the electron donor to the reaction center chlorophyll of PS I (P700) but also to the reaction center chlorophyll of PS II (P680). Other unconventional findings include evidence that the fully functional oxygenic photosystem, when operating separately from the anoxygenic photosystem, reduces plastoquinone to plastoquinol and subsequently oxidizes plastoquinol by two pathways acting in concert: one being the universally recognized DBMIB-sensitive pathway via the Rieske iron-sulfur center of the cytochrome bf complex and the other, a hitherto unrecognized, DBMIB-insensitive electron transport pathway around P680 that centers on cytochrome b-559. These nonconforming findings form the basis of an alternate hypothesis of photosynthetic electron transport that modifies and complements the Z scheme.

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Section: Introductionmentioning

confidence: 99%

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Arnon

1995

Photosynth Res

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“…Since the experiments were highly intricate, it was far from easy to resolve this disagreement. In a final paper, Warburg et al (1969) published experimental results in agreement with the value of 12 photons per oxygen, but still interpreted them, wrongly, in our opinion, as 3 photons per oxygen molecule (Govindjee, 1999). In a long series of experiments, Yuan et al (1955) obtained requirements of 8.7 ± 1.0 photons per molecule of carbon dioxide assimilated, and 9.1 ± 1.1 photons per molecule of oxygen evolved.…”

Section: Quantum Yieldsmentioning

confidence: 96%

Evolution of the Z-Scheme of Electron Transport in Oxygenic Photosynthesis

Björn

Nickelsen

2013

Advanced Topics in Science and Technology in China

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Abstract:We start with the discussion of the photosynthetic unit, based on the experiments of Arnold (1932a, 1932b), continue with the first two-quantum proposal by Rabinowitch (1945Rabinowitch ( , 1956), Emerson's Red drop (1943) and Emerson Enhancement Effect (1957) and various action spectra made for understanding the roles of the photosynthetic pigments. The experimental work of Kok (1959) and the theoretical model by Hill and Bendall (1960) were followed soon thereafter by the seminal papers of Duysens et al. (1961) and Duysens and Amesz (1962), in which the two photosystems were shown to be connected, in series, by cytochrome, which can be photooxidized by photo system I and photoreduced by photosystem II. Further, Witt et al. (1961) and others, cited in this paper, made refinement of the Z-scheme.

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“…It seemed to have had a special attraction for some of the most illustrious chemists in their day, e.g., von Baeyer 2883 (4) and Willsttfiter (5); its last great contemporary protagonist was Otto Warburg (6). After de Saussure (7) showed that water is a reactant in photosynthesis, the C02 cleavage hypothesis readily accounted for the deceptively simple overall photosynthesis equation (Eq.…”

Section: Early Conceptsmentioning

confidence: 99%

The Light Reactions of Photosynthesis

Arnon

1971

Proc. Natl. Acad. Sci. U.S.A.

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Historically, the role of light in photosvnthesis has been ascribed either to a photolysis of carbon dioxide or to a photolysis of water and a resultant rearrangement of constituent atoms into molecules of oxygen and glucose (or formaldehyde). The discovery of photophosphorylation demonstrated that photosynthesis includes a light-induced phosphorus metabolism that precedes, and is independent from, a photolysis of water or CO2. ATP formation could best be accounted for not by a photolytic disruption of the covalent bonds in C02 or water but by the operation of a light-induced electron flow that results in a release of free energy which is trapped in the pyrophosphate bonds of ATP.Photophosphorylation is now divided into (a) a noncyclic type, in which the formation of ATP is coupled with a light-induced electron transport from water to ferredoxin and a concomitant evolution of oxygen and (b) a cyclic type which yields only ATP and produces no net change in the oxidation-reduction state of any electron donor or acceptor. Reduced ferredoxin formed in (a) serves as an electron donor for the reduction of NADP by an enzymic reaction that is independent of light. ATP, from both cyclic and noncyclic photophosphorylation, and reduced NADP jointly constitute the assimilatory power for the conversion of C02 to carbohydrates (3 moles of ATP and 2 moles of reduced NADP are required per mole of C02).Investigations, mainly with whole cells, have shown that photosynthesis in green plants involves two photosystems, one (System II) that best uses light of "short" wavelength (X < 685 nm) and another (System I) that best uses light of "long" wavelength (X > 685 nm). Cyclic photophosphorylation in chloroplasts involves a System I photoreaction. Noncyclic photophosphorylation is widely held to involve a collaboration of two photoreactions: a short-wavelength photoreaction belonging to System II and a long-wavelength photoreaction belonging to System I. Recent findings, however, indicate that noncyclic photophosphorylation may include two short-wavelength, System II, photoreactions that operate in series and are joined by a "dark" electron-transport chain to which is coupled a phosphorylation site. Early conceptsThe first hypothesis about the role of light in photosynthesis came very appropriately from Jan Ingenhousz, who some years earlier had made the epochal discovery that it is "the influence of the light of the sun upon the plant" (1) that is responsible for the "restorative" effect of vegetation on "bad" air-an observation first made in 1771 by Joseph Priestley without reference to light (2). In 1796, Ingenhousz wrote that the green plant absorbs from "carbonic acid in the sunshine, the carbon, throwing out at that time the oxygen alone, and keeping the carbon to itself as nourishment" (3).The idea that light liberates oxygen by photodecomposing C02 had, with some modifications, persisted for well over a century. It seemed to have had a special attraction for some of the most illustrious chemists in their day, e.g., von ...

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Chlorophyll Catalysis and Einstein's Law of Photochemical Equivalence in Photosynthesis

Cited by 15 publications

References 4 publications

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Divergent pathways of photosynthetic electron transfer: The autonomous oxygenic and anoxygenic photosystems

Evolution of the Z-Scheme of Electron Transport in Oxygenic Photosynthesis

The Light Reactions of Photosynthesis

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