Photosynthesis by Isolated Chloroplasts

Arnon, Daniel I.; Allen, Mary; Whatley, F. R.

doi:10.1038/174394a0

Cited by 419 publications

(118 citation statements)

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“…One concept, espoused by Warburg et al (3), was that photosynthetic quantum conversion has an efficiency of about 90%-i.e., that energy equivalent to that of 3 einsteins of red quanta (42 kcal each) is sufficient to liberate 1 mol of 02 (corresponding to 1/6 mol of glucose, for which AGO' = 686/6 = 114 kcal). In contrast, Emerson (4) and his followers (5) concluded that photosynthetic efficiency was much lower, of the order of 8 to 12 quanta per 02, a range that is widely accepted today even though values less than 8 have, at times, been obtained by investigators (6,7) who did not share Warburg's conclusions.…”

mentioning

confidence: 82%

“…With chloroplasts from young plants, these quantum requirements for a concurrent formation of ATP and NADPH add up to a requirement of 12 quanta for the generation of the NADP+ (2.5 mM) was added where indicated. Experimental conditions not otherwise specified were as in Table 1. two NADPH and the three ATP that are consumed in the assimilation of one CO2 to the level of glucose (43).…”

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Quantum efficiency of photosynthetic energy conversion.

Chain¹,

Arnon²

1977

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

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The quantum efficiency of photosynthetic energy conversion was investigated in isolated spinach chloroplasts by measurements of the quantum requirements of ATP formation by cyclic and noncyclic photophosphorylation catalyzed by ferredoxin. ATP formation had a requirement of about 2 quanta per 1 ATP at 715 nm (corresponding to a requirement of 1 quantum per electron) and a requirement of 4 quanta per ATP (corresponding to a requirement of 2 quanta per electron) at 554 nm. When cyclic and noncyclic photophosphorylation were operating concurrently at 554 nm, a total of about 12 quanta was required to generate the two NADPH and three ATP needed for the assimilation of one CO2 to the level of glucose.Few areas of photosynthesis have received more intensive theoretical and experimental study and generated more controversy than the efficiency with. which photosynthetic cells convert the electromagnetic energy of light into chemical energy (for review, see refs. 1 and 2). Two different concepts, never reconciled during the lifetimes of their main protagonists, emerged from the many investigations. One concept, espoused by Warburg et al. (3), was that photosynthetic quantum conversion has an efficiency of about 90%-i.e., that energy equivalent to that of 3 einsteins of red quanta (42 kcal each) is sufficient to liberate 1 mol of 02 (corresponding to 1/6 mol of glucose, for which AGO' = 686/6 = 114 kcal). In contrast, Emerson (4) and his followers (5) concluded that photosynthetic efficiency was much lower, of the order of 8 to 12 quanta per 02, a range that is widely accepted today even though values less than 8 have, at times, been obtained by investigators (6, 7) who did not share Warburg's conclusions.Most studies of photosynthetic quantum efficiency were based on measurements of light-induced production of 02 (corrected for concurrent respiration) during complete photosynthesis by whole cells, usually unicellular algae of the Chlorella type. Discordant results were attributed to experimental variables such as errors in methods (usually manometric) of 02 measurement, variations in the concurrent 02 consumption by respiration, participation of respiratory intermediates in photosynthesis, need for supplementary (catalytic) illumination, and nutritional history, age, and physiological status of the cells (1-5). Left unchallenged, however, was the main (and, to us, dubious) premise underlying these studies with whole cells-namely, that the photoproduction of 1 mol of 02 always corresponds to the assimilation of 1 mol of CO2 to the level of glucose and that, therefore, 02 evolution is a reliable measure of the total amount of chemical energy stored.A different perspective and experimental approach to the question of photosynthetic quantum efficiency emerged from studies of photosynthesis by isolated chloroplasts in which the process was physically separated into a light phase concerned with cyclic and noncyclic photophosphorylation and a "dark," enzymatic phase concerned with the assimilation of CO2 (8).Fractiona...

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confidence: 82%

mentioning

confidence: 99%

Quantum efficiency of photosynthetic energy conversion.

Chain¹,

Arnon²

1977

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

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“…Usually this takes the form of some degree of swelling, the interlamellar separation being twice or more the normal value. When the chloroplasts are isolated in a medium similar to that used in recent photosynthetic studies (15) prior to fixation, more severe swelling and disorganization are apparent (Fig. 9).…”

Section: Chloroplast Structure and Swellingmentioning

confidence: 99%

Effects of the Physical Environment on Some Lipoprotein Layer Systems and Observations on Their Morphogenesis

Hodge

1956

The Journal of Cell Biology

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PLATES 74 ~ 75The sensitivity of lipoprotein layer systems to their physical environment is well known. One may cite for instance the occurrence of "myelin forms," which arise under certain conditions from a number of paracrystalline lipoprotein layer systems. It is a common observation that lipoprotein systems such as mitochondria, chloroplasts, and similar organelles (including the endoplasmic reticulum (ER)) swell rapidly when isolated in hypotonic media (and even in so called physiological media), and in view of the intensive effort currently directed toward biochemical investigation of such systems, it is of importance to determine the effects of this isolation on their fine structure.During the course of several investigations 1 on the structure (1, 2) and development (3) of chloroplasts and of the endoplasmic reticulum in the plant cell in relation to the isolated microsome fraction (4), a number of observations have been made which seem to throw some light on the structural changes accompanying swelling phenomena. It will be shown that such membrane systems exhibit a generalized swelling response, viz., a strong tendency, understandable in general physical chemical terms, to round up into the form of spherical vesicles. Concerning developmental aspects, the evidence suggests that the endoplasmic reticulum of Nitella, which is characterized in the mature cell by a moderately complex arrangement of tubules, cisternae, and other elements, arises by fusion or coalescence of small spherical vesicles (3). Similarly, the lamellae of Zea chloroplasts (2) appear to arise in the first instance by 1 The results described here have been derived from a number of investigations carried out in collaboration with Dr.

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“…Despite the fact that cyclic photophosphorylation has been discovered more than 20 years ago [1,2], the electron transport components reacting in this photosystem-I-dependent pathway are still not ascertained. Photooxidation of cytochrome hg, a specific component of cyclic electron flow [3,4], appears to involve a number of components common to both cyclic and non-cyclic electron transport [4-61.…”

mentioning

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On the Role of Ferredoxin and Ferredoxin‐NADP⁺Reductase in Cyclic Electron Transport of Spinach Chloroplasts

Böhme

1977

European Journal of Biochemistry

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Antibodies prepared against purified spinach ferredoxin and ferredoxin‐NADP+ reductase were used as specific inhibitors of electron‐transfer reactions dependent on either ferredoxin or ferredoxin‐NADP+ reductase. The possible role of both electron carriers in cyclic electron transport was checked using cytochrome b6 photoreactions as indicator. It could be demonstrated that the ferredoxin antibody inhibits cytochrome b6 photoreduction. Ferredoxin‐NADP+ reductase, however, appears not to be involved in this pathway: reductase antibody in concentrations sufficient to completely inhibit electron transport to NADP+ had no effect on cytochrome b6 photoreduction. Quantitative treatment of the immunoassay data showed that osmotically shocked chloroplasts contain both bound ferredoxin and ferredoxin‐NADP+ reductase in concentrations approximately equal to that of cytochrome b6.

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Photosynthesis by Isolated Chloroplasts

Cited by 419 publications

References 11 publications

Quantum efficiency of photosynthetic energy conversion.

Quantum efficiency of photosynthetic energy conversion.

Effects of the Physical Environment on Some Lipoprotein Layer Systems and Observations on Their Morphogenesis

On the Role of Ferredoxin and Ferredoxin‐NADP⁺Reductase in Cyclic Electron Transport of Spinach Chloroplasts

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Photosynthesis by Isolated Chloroplasts

Cited by 419 publications

References 11 publications

Quantum efficiency of photosynthetic energy conversion.

Quantum efficiency of photosynthetic energy conversion.

Effects of the Physical Environment on Some Lipoprotein Layer Systems and Observations on Their Morphogenesis

On the Role of Ferredoxin and Ferredoxin‐NADP+Reductase in Cyclic Electron Transport of Spinach Chloroplasts

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On the Role of Ferredoxin and Ferredoxin‐NADP⁺Reductase in Cyclic Electron Transport of Spinach Chloroplasts