Emerson Effect Research Articles

Near‐Infrared Nanophosphor Embedded in Mesoporous Silica Nanoparticle with High Light‐Harvesting Efficiency for Dual Photosystem Enhancement

AbstractLight‐harvesting and conversion ability is important to promote plant growth, and especially when resources are limited. A near‐infrared (NIR) nanophosphor embedded with mesoporous silica nanoparticles (MSN), ZnGa2O4:Cr3+,Sn4+(ZGOCS), was developed and its optical properties were harnessed to enhance the photosynthetic ability ofBrassica rapa spp. chinensis. The broad excitation of ZGOCS from the ultraviolet to the visible region allowed the conversion of extra light into near‐infrared light (650–800 nm) and thus promoted the dual photosystem via the Emerson effect. ZGOCS@MSN was spherical with a size of 65±10 nm and good dispersion. A light conversion ability of up to 75 % under different wavelengths was achieved. Moreover, the electron transfer rate of photosynthesis increased by 100 % with a suitable ZGOCS@MSN concentration. Plant and animal models were used to explore the effects of the nanophosphor. ZGOCS@MSN distribution was tracked by monitoring its NIR emission in plant and animal tissues, demonstrating that this nanophosphor can be potentially utilized in plant growth.

Near‐Infrared Nanophosphor Embedded in Mesoporous Silica Nanoparticle with High Light‐Harvesting Efficiency for Dual Photosystem Enhancement

Light-harvesting and conversion ability is important to promote plant growth, and especially when resources are limited. A near-infrared (NIR) nanophosphor embedded with mesoporous silica nanoparticles (MSN), ZnGa2 O4 :Cr3+ ,Sn4+ (ZGOCS), was developed and its optical properties were harnessed to enhance the photosynthetic ability of Brassica rapa spp. chinensis. The broad excitation of ZGOCS from the ultraviolet to the visible region allowed the conversion of extra light into near-infrared light (650-800 nm) and thus promoted the dual photosystem via the Emerson effect. ZGOCS@MSN was spherical with a size of 65±10 nm and good dispersion. A light conversion ability of up to 75 % under different wavelengths was achieved. Moreover, the electron transfer rate of photosynthesis increased by 100 % with a suitable ZGOCS@MSN concentration. Plant and animal models were used to explore the effects of the nanophosphor. ZGOCS@MSN distribution was tracked by monitoring its NIR emission in plant and animal tissues, demonstrating that this nanophosphor can be potentially utilized in plant growth.

Opening the Window on Higher Ed: An Interview with Christopher Newfield

Opening the Window on Higher Ed:An Interview with Christopher Newfield Jeffrey J. Williams (bio) The cost of college has skyrocketed, limiting access and causing the exponential growth of student debt. This is typically cast as a result of inevitable economic or historical change. Against that complacent view, Christopher Newfield shows how debt and many other current problems in American higher education arise from deliberate policies and politics, and he has become a leading figure in critical university studies. While most university budgets are forbiddingly complicated if not secret, in Unmaking the Public University: The Forty-Year Assault on the Middle Class (2008) Newfield traces the money trail and the ways that state universities have been defunded, with support diverted from public uses to private coffers. And while reformers and administrators might target particular problems, in The Great Mistake: How We Wrecked Public Universities and How We Can Fix Them (2016) he calls attention to the "devolutionary cycle," with problems like cuts in public funding answered by raising tuition, prompting rising student debt, in turn causing lack of confidence in public education, and so on, in an interlinking spiral. Overall, he argues that we need to reinfuse public higher education and the value of humanistic thinking for human development. Starting as a scholar of American literature, Newfield has focused on cultural politics and ideology, particularly the tension between liberal individualism and democratic equality. That tension is the topic of his first book, The Emerson Effect: Individualism and Submission in America (1996), which analyzes Ralph Waldo Emerson's imprint on American culture, which extols self-reliance but finally encourages "submissive individualism." Through the 1990s, Newfield turned to look at management culture and how it recirculates those values, writing on management theorist Tom Peters. In addition, he co-edited two collections about contemporary cultural politics, After Political Correctness: The Humanities and Society in the 1990s (with Ronald Strickland; 1995) and Mapping Multiculturalism (with Avery Gordon; 1996). Relevant to this interview, see also his essays, "What Was 'Political Correctness'?: Race, the Right, and Managerial Democracy in the Humanities" (Critical Inquiry 19.2 [1993]); "Recapturing Academic Business" (Social Text 15.2 [1997]); and "Corporate Culture Wars" (Corporate Futures, ed. George Marcus [1998]). [End Page 743] Over the past two decades, Newfield has focused on the American university. His study of management culture fed into his analysis of the development of the research university in Ivy and Industry: Business and the Making of the American University, 1880-1980 (2003). In addition to his books Unmaking the Public University and The Great Mistake, and numerous essays and reports, he also co-founded, co-edits, and sometimes writes for the site, Remaking the University, at http://utotherescue.blogspot.com/, an influential clearinghouse for discussion of contemporary issues and events in higher education, especially in large public systems such as California's. Born in 1958, Newfield grew up in Los Angeles and attended Reed College (BA, 1980) and Cornell University (PhD, 1988). After a brief sojourn at Rice University (1987-89), he taught at UC-Santa Barbara from 1989 to 2020, where he is Distinguished Professor emeritus. Since 2020, he is Director of Research at the Independent Social Research Foundation in London. This interview took place on July 16, 2021 via Zoom, with Newfield speaking from London. It was conducted by Jeffrey J. Williams in Pittsburgh, and transcribed by Bethie Wang, an MA in literary and cultural studies from Carnegie Mellon University. Jeffrey J. Williams: Over the past two decades, you have probably been the most persistent critic of higher education from the humanities. Could you encapsulate your analysis of contemporary higher education? Christopher Newfield: One overriding theme has been the shifting away from public to private rationales for higher education, which has been a disaster. This has been happening throughout my career, but was accelerated by the financial crisis. For example, there's been enormous state support for asset prices since the 1980s, starting when Greenspan was head of the Fed, through cheap money—that is, the constant flooding of the financial system whenever market prices start to fall with public dollars. That is very much the opposite of the state's treatment of the public sector...

Far-Red Carbon Dots as Efficient Light-Harvesting Agents for Enhanced Photosynthesis.

Sunlight utilization by plants via the photosynthesis process is limited to the visible spectral range. How to expand the utilization spectral range via construction of a hybrid photosynthetic system is a hot topic in this field. In this work, far-red carbon dots (FR-CDs) with excellent water solubility, good biocompatibility, high quantum yield (QY), and superior stability were prepared by a one-step microwave synthesis in 3 min. The as-prepared FR-CDs is an efficient converter transferring ultraviolet A (UV-A) light to 625-800 nm far-red emission, which can be directly absorbed and utilized by chloroplasts. Due to the broader spectral utilization of solar energy and Emerson effect, increased photosynthetic activity can be achieved both in vivo and in vitro when applied for Roman lettuce. The in vitro hybrid photosynthetic system via coating chloroplasts with FR-CDs presents higher electron transfer efficiency between PS II (photosystem II) to PS I (photosystem I), which consequently increases the ATP production. The in vivo experiment further confirms that FR-CDs-treated lettuce can induce a 28.00% higher electron transfer rate compared with the control group, which results in 51.14 and 24.60% enhancement of fresh and dry weights, respectively. This work is expected to provide a way for improving the conversion efficiency from solar energy to chemical energy. (PS II) to photosystem I (PS I), which consequently increases the ATP production. The in vivo experiment further confirms that FR-CDs-treated lettuce can induce a 28.00% higher electron transfer rate compared with the control group, which results in 51.14 and 24.60% enhancement of fresh and dry weights, respectively. This work is expected to provide a way for improving the conversion efficiency from solar energy to chemical energy.

Photochemical response of parsley (Petroselinum crispum (Mill.) Fuss) grown under red light: The effect on the essential oil composition and yield

The effect of different wavelengths on plants morphological characters has been widely described, but also the chemical composition of the essential oil is influenced by the lighting conditions in which they are grown. In the present study, the effect of both the enrichment (reverse Emerson effect) and the monochromatic lighting treatments with red light has been evaluated on the essential oil compositions of parsley (Petroselinum crispum (Mill.) Fuss). Multivariate statistical analysis was performed on the results, with both the hierarchical cluster and principal component analyses. Whilst the red-enrichment of the light spectrum did not induce major changes in the essential oil composition, the end of the day monochromatic red (660 nm) treatment caused a chemotype switch in the essential oil and relevant differences in the overall composition, with an increment of the relative abundance of oxygenated compounds, coupled with a relevant decrement in the abundance of phenylpropanoids. The extraction yields remained unchanged in all the three tested conditions of light (control, red-enriched and monochromatic red). Different lighting conditions could be used as a tool to modulate the compounds present in the essential oil, but further studies would be advisable to assess the effects on different species and chemical classes of compounds.

Effect of Long-Period Ordering of the Structure of a Plant on the Initial Stages of Photosynthesis

Using data on the structure of plant leaves, specific features of light propagation in biophotoniccrystal structures have been established by the transfer matrix method. Splitting of the stopband in two bands has been found. The density of photonic states and the electromagnetic field value have been calculated. The occurrence of two photosystems (splitting of the stopband in two bands), the peculiarity of the long-wavelength quantum yield and its enhancement (Emerson effect), and water dissociation in the soft mode due to an increase in the electromagnetic field on the layers are explained.

Far-Red Spectrum of Second Emerson Effect: A Study Using Dual-Wavelength Pulse Amplitude Modulation Fluorometry

Non-additive enhancement of the photosynthesis excited by simultaneous illumination with far-red light and light of shorter wavelengths is called as "second Emerson effect". Its action spectra are well-known as a photosynthetic yield's dependence on light wavelength in red (630-690 nm) spectral region at a constant-wavelength far-red illumination near 700-715 nm. However, the opposite dependence of the photosynthetic yield's of shorter constant-wavelength light (red or blue) on light wavelength in far-red (690-760 nm) spectral region was never studied. In this study the action spectrum of second Emerson effect was studied using a fast-Fourier dual-wavelength Pulse Amplitude Modulation (PAM) fluorometry. Chlorophyll fluorescence in ailanthus (Ailanthus altissima Mill.) leaves was excited with blue modulated light. Far-red induced decrease of fluorescence (fluorescence shift-FRIFS) was studied in response to illumination of leaves with a background light from 690 to 760 nm (10 nm step), calculating FRIFS = (F0-Fs)/F0, where F0-fluorescence measured without and Fs-with far-red light. Maximum FRIFS was observed at 720 nm (11.8%), but it still remained considerable at 740, 750 nm and a low FRIFS values were revealed at 690 and even at 760 nm. Measurements carried out with blue saturating flashes during and after far-red illumination showed the increase of quantum yield of Photosystem II (PSII), calculated as Fv/Fm at 720 nm background light. FRIFS had lower values under excitation with red modulating light. It is concluded that FRIFS is a result of a photochemical quenching caused by an additional selective far-red excitation of PSI in conditions when PSII is preferably excited by blue light thus leading the PSI to limit non-cyclic electron flow. The contradiction between the known absorption spectra of PSI-light harvesting complex I and the observed action spectrum of second Emerson effect (FRIFS spectrum) is discussed.

Ivy and Industry: Business and the Making of the American University, 1880-1980 (review)

Reviewed by: Ivy and Industry: Business and the Making of the American University, 1880–1980 Albert H. Teich (bio) Ivy and Industry: Business and the Making of the American University, 1880–1980. By Christopher Newfield. Durham, N.C.: Duke University Press, 2003. Pp. 290. $32.95. Twenty-first-century research universities are widely viewed as engines of economic growth for their communities, regions, and nations. Virtually all top research universities and most aspiring institutions have technology-transfer and licensing offices whose function is to exploit the results of their faculty's research in the commercial arena. Many have research parks intended to cultivate start-up companies and/or attract existing businesses. A growing number of universities employ lobbyists to persuade congressional representatives to appropriate funds directly to them, usually with the expectation that such "pork barrel" appropriations will bring economic benefits to their states or districts. Much has been written on the commercialization of academic research, especially since the passage of the Bayh-Dole Act in 1980. This law, which allowed universities to take ownership of patents arising from federally sponsored research, is widely regarded as a watershed in university-industry relations. Christopher Newfield's Ivy and Industry, which looks at the development of those relations in the century before Bayh-Dole, puts their [End Page 852] recent evolution in a useful long-term perspective. An English professor at the University of California at Santa Barbara, Newfield seems an unlikely writer to address this subject; his previous works include books titled The Emerson Effect: Individualism and Submission in America (1996) and Mapping Multiculturalism (1996). His analysis here is enriched, however, by his personal experience at Reed College, Cornell, and Rice, as well as Santa Barbara. Newfield sees research universities as having been a central component of the U.S. industrial system since the post–Civil War era. They supplied knowledge and managers for the emerging industrial economy. At the same time, they provided a home for "non-utilitarian knowledge" and curiosity-driven research. And they gave the professional middle class a humanistic perspective on themselves and society. A key aspect of Newfield's book, one that differentiates it from others on this subject, is its focus on what he calls "this double-edged industrial role." The author examines the ways in which corporate styles of management and business considerations have permeated the university. He examines the internal workings of the university, which he sees as subject to a dual management system—a corporate-style business side that runs the institution and sets policy, and an academic side controlled by the faculty. While some observers term this "shared governance," Newfield prefers to call it "divided governance," emphasizing the limits on the ability of the faculty to wield decision-making authority. In his view, the system serves the science faculty (in which individual academic entrepreneurs thrive) better than the humanities faculty, which he sees as beset by bureaucracy, vulnerable to business influences, and limited in its freedom of action. Nonetheless, he views the university as permanently dependent on humanism and he traces the response of humanists to the growing domination of the university by business. Newfield carries his analysis into the present, examining the impact of increased government interest in and support for stronger ties between universities and industry. This interest is a result of pressures from policymakers for practical results (i.e., economic benefits, jobs, international competitiveness) from the billions of federal dollars that are spent each year on academic research. He sees difficult challenges in these demands: the need for university research to maintain its independence in the face of commercial pressures; the need to reconcile the university's two missions of economic and personal development; and the need for universities to change as faculties and student bodies become increasingly diverse. This is not a book for policy wonks. It prescribes no courses of action, no approaches to solving the problems it identifies. But it is a provocative work. It offers humanists a way to think about the dilemmas their disciplines face in an increasingly technological environment. And it offers scientists, [End Page 853] technologists, and historians of science and technology an opportunity to see their domains from a perspective...

The Emerson Effect: Individualism and Submission in America.

This work presents a revisionist account of Ralph Waldo Emerson's influential thought on individualism, in particular his political psychology. The author analyzes the interplay of liberal and authoritarian impulses in Emerson's work in various domains: domestic life, the changing New England economy, theories of poetic language, homoerotic friendship, and racial hierarchy. Focusing on neglected later writings, Newfield shows how Emerson explored the tensions between autonomy and community - and consistently resolved these tensions by abandoning crucial elements of both and redefining autonomy as a kind of liberating subjection. He argues that in Emersonian individualism, self-determination is accompanied by submission to authority, and examines the influence of this submissive individualism on the history of American liberalism. In a reading of Emerson's early and neglected later works, the study analyzes Emerson's emphasis on collective, or corporate, world-building, rather than private possession. Tracing the development of this corporate individualism, he illuminates contradictions in Emerson's political outlook, and the conjunctions of liberal and authoritarian ideology they produced.

Charles Stacy French: A tribute

Charles Stacy French, one of the great men of photosynthesis research, died on 13 October 1995. He received his PhD at Harvard University where he associated with William Arnold, Caryl Haskins, later president of the Carnegie Institution of Washington, and Pei-Sung Tang. He did early work on the photosynthesis of photosynthetic bacteria with Robert Emerson and later with Otto Warburg. French worked for three years with James Franck in Chicago. His associates there included Hans Gaffron, Robert Livingston, Warren Butler and Roderick Clayton. After spending three years at the University of Minnesota he became the director of the Department of Plant Biology of the Carnegie Institution of Washington and remained there until he retired in 1973. French's research career at the Carnegie Institution was marked by the development of novel and ingenious pieces of equipment such as the French pressure cell used to prepare chloroplast particles to measure partial reactions of photosynthesis. He developed the first recording fluorescence spectrophotometer and demonstrated efficient energy transfer between certain photosynthetically-active pigments, a spectrophotometer that measured the first derivative of absorbance, as well as a novel analog computer to show that complex absorption curves in living plants are produced by a number of distinct forms of chlorophyll occurring in vivo. French used the Blinks rate-measuring oxygen electrode to measure action spectra of oxygen evolution by photosynthesis automatically. He and Jack Myers did some of the pioneering work on the Emerson effect showing the necessary cooperation of two photosystems in photosynthesis. French used the Carnegie Institution's fellowship program to bring large numbers of scientists from around the world to his laboratory. When Stacy French died in 1995, the field of photosynthesis lost one of its great and early pioneers.

Characterization of thermal damage to the photosynthetic electron transport system in potato leaves

Fluorescence, absorbance and photoacoustic methods were used to examine in situ various functional aspects of the photochemical apparatus of chloroplasts in potato leaves ( Solanum tuberosum L.) briefly pre-exposed in the dark to a wide range of elevated temperatures (32°C–45°C). Measurements of the Emerson enhancement of photosynthetic O 2 evolution and the flash-induced reduction of the oxidized reaction center pigment of photosystem I demonstrated that selective denaturation of photosystem II in potato leaves started at a ‘low’ temperature of 32°C. Analysis of the characteristics of chlorophyll fluorescence induction in sub- and super-saturating light revealed two targets of mild heat stress: (i) an irreversible inhibition of electron donation to PSII and (ii) a reversible reduction of excitation energy trapping by the PSII reaction centers, with the former effect being identified as the major determinant of the loss of photosynthesis. A second phase of thermal denuration of photosystem II occurred at temperatures higher than around 38°C, resulting in a dramatic loss of PSII-mediated electron transport. Measurements of chlorophyll fluorescence decay kinetics after short and long flashes of intense light indicated that high temperatures up to 42°C had no inhibitory effect on the acceptor side of photosystem II: the rate of electron transfer from the primary (Q A) to the secondary (Q B) electron acceptor of photosystem II and the fraction of Q B-non-reducing photosystem-II centers remained unchanged whereas the intersystem electron flow appeared to be stimulated. It was also observed that photosystem-I photochemistry, as probed by the photochemical energy storage in far-red light, the quantum yield of photosystem I for the Emerson effect and the kinetics of P 700 photooxidation by strong far-red light, was fully preserved in heat-treated potato leaves (at least, up to 45°C). From the presented data, one can propose the following sequence of events leading to the loss of photosynthetic electron transport in heated potato leaves: inhibition of water splitting (at leaf temperatures higher than 32°C)< reduced efficiency of energy trapping by photosystem II centers < alteration of the electron flow after Q A ( > 42° C) < PSI ( > 45° C) .

Prolonged chilling under moderate light: effect on photosynthetic activity measured with the photoacoustic method

Abstract Exposure of tomato plants to a mild chilling temperature and relatively low ambient photon flux density for an extended period (10°C and 400 μmol photons m−2 s−1 d and 5°C night for 6 d) resulted in a significant decrease in the variable chlorophyll fluorescence, the quantum yield of oxygen evolution and the amount of total absorbed energy stored in photochemical intermediates, but not in the chlorophyll concentration or in the activity of ribulose biphosphate carboxylase. These results indicate that photochemical processes involving PSII were affected, and might reflect photoinhibitory effects on the photosynthetic apparatus.Chilling treatment had relatively small influence on the maximal extent of the Emerson effect. This observation, together with the sharp decrease found in the quantum yield of oxygen evolution, could be reconciled with the above results only if some dependency between the two photosystems was assumed. On the basis of this interpretation, it was concluded that the strong Emerson effect after chilling still reflects the typical imbalance between PSI and PSII centres, even though populations of such unaffected pairs are smaller than in the untreated plants.The relatively new photoacoustic technique employed in this study is shown to be useful both as a diagnostic tool and as a means of investigating changes in photochemical activity in the study of environmental stress effects on photosynthesis. The results support the view that photoinhibition can play an important role in limiting photosynthetic activity, and therefore productivity, in chilling‐sensitive plants such as the tomato under the natural conditions that prevail during the winter in mediterranean climates.

The Role of Cyclic and Pseudocyclic Photophosphorylation in Photosynthetic14CO2Fixation inHydrodictyon africanum

Experiments are reported in which the effects on photosynthesis of various inhibitors of cyclic photophosphorylation were investigated. These inhibitors, generally had only a small inhibitory effect on photosynthesis, and the inhibition was not increased by conditions which inhibit pseudocyclic photophosphorylation. These inhibitors do not inhibit the Emerson enhancement effect. From these results it was concluded that photosynthesis does not need any ATP other than that produced in non-cyclic photophosphorylation. The effects of these inhibitors on active K influx in light-anaerobic conditions in the presence or absence of C02 suggest that some of the ATP produced by non-cyclic photophosphorylation can be used to support active K influx. The results are discussed in relation to the mechanism of the Emerson effect, the stoichiometry of non-cyclic photophosphorylation, and the ATP requirements for autotrophic growth.

ON THE EMERSON ENHANCEMENT EFFECT IN THE FERRICYANIDE HILL REACTION IN CHLOROPLAST FRAGMENTS*

Abstract— The Emerson effect is demonstrated in the ferricyanide Hill reaction when the rates of steady‐state oxygen evolution are measured in spinach chlorplast fragments exposed to red (650 nm) and far‐red (700 nm) light of high but not saturating intensity. However, at very low light intensity, the Emerson effect could not be observed. These experiments suggest that ferricyanide can be reduced at two sites. At low light intensity, the rate at one site predominates and at this site one photochemical system is active. At high light intensity, however, the action at a site that is dependent on the cooperation of two photochemical systems predominates.The action spectra of the ferricyanide Hill reaction measured in the presence of an excess of 650 nm or in the excess of 700 nm light show two peaks: one at 650 nm due to chlorophyll b and the other around 675 nm due to chlorophyll a. The ratio of chlorophyll a to chlorophyll b peaks is about 1.4 when 650 nm background light is used; the same ratio is about 0.7 with 700 nm background light. The two pigment systems seem to contain both chlorophyll a and chlorophyll b but in different proportions.

A theory of light utilization in plant photosynthesis

A model for the photochemical steps in photosynthesis is described in which only one type of reaction center participates in the chemical conversion of excitation energy. Two types of energy-collecting pigment systems can occur, but in distinction to most current models the energy is delivered to a unique type of chlorophyll-enzyme complex. Of the two photochemical steps in photosynthesis, one is mediated by the metastable triplet state of chlorophyll in this complex and the other requires singlet excitation for efficient operation. The nature of chlorophyll in the two pigment systems is identified on the basis of spectroscopic evidence. The far-red absorbing pigment, P700, is considered to be a crystallized chlorophyll that may participate in photosynthetic energy collection but is not essential for the overall process. The model is tested by comparisons with experimental evidence from fluorescence, afterglow, the Emerson effect, reversible bleaching, and alternate photochemical pathways.

Role of two photosynthetic pigment systems in cytochrome oxidation, pyridine nucleotide reduction, and fluorescence

The investigations of two light reactions in photosynthesis driven by different pigment systems started with Emerson’s discovery that in the green alga Chlorella pyrenoidosa the rate of photosynthesis in light beams of 700 and 650 applied simultaneously, was higher than the sum of the rates in each beam separately (Emerson, Chalmers &amp; Cederstrand 1957). This effect has been called ‘Emerson effect’ or ‘enhancement effect’. Since the quantum efficiency of light of 700 mp, compared with that of 650 mpwas rather low, the increase in rate in the two beams was attributed to an enhancement of the photosynthetic efficiency of light of 700 nip, by light of 650 mp. In this paper we will present evidence that the rate of photosynthesis at both wavelengths is enhanced. Action spectra for the Emerson effect were determined by measuring the extra increase in photosynthesis obtained by adding light of various wavelengths to constant illumination of 700 mp. The action spectrum for the Emerson effect in Chlorella showed maxima at 650 and 480 mp, which indicated that light absorbed by chlorophyll b was particularly effective in the enhancement. In the red alga Porphyridium cruentum photosynthesis brought about by light absorbed in the region around 680 mp was ‘enhanced’ by light absorbed by the phycobilins phycocyanin and phycoerythrin (Brody &amp; Emerson 1959). It was concluded that efficient photosynthesis was only possible, if at least one of the accessory pigments was excited (Emerson et al. 1957; Brody &amp; Emerson 1959).

Emerson Effect in Isolated Chloroplasts

THE oxygen production resulting from flash illumination of chloroplast fragments was determined, using the method previously described1. Spinach leaves were ground in 0.35 M sodium chloride, 0.037 M magnesium chloride, 0.01 M ascorbate and 0.1 M tris buffer adjusted to pH 7.6. After centrifugation, the chloroplasts were washed once in the grinding medium but without ascorbate and broken in the same medium diluted ten times. The reaction mixture contained, in a final volume of 2 ml., chloroplast fragments containing 0.15 mg chlorophyll and the following (in µmoles): potassium ferricyanide, 3; sodium chloride, 70; magnesium chloride, 10; adenosine triphosphate, 1.5; inorganic phospate, 30; tris buffer, 50, adjusted to pH 7.4. Throughout the measurements the reaction mixture was maintained at 5° ± 1° C and was flushed with nitrogen gas containing less than 1 p.p.m. oxygen. Flashes, from Philips photoflux bulbs, were of sufficient intensity to saturate the reaction (2.8 × 10−6 lumens, 35-msec duration). The change of oxygen yield per single flash was used to determine the rate of decline of activity of the chloroplasts with time.

Effects of red and far-red light on the fluorescence yield of chlorophyll in vivo

The fluorescence of chlorophyll a and C-705 in green leaves has been investigated during the induction period of photosynthesis in air and in nitrogen. A brief illumination of a leaf with red light causes an increased yield of chlorophyll a fluorescence which persists for a longer period in nitrogen than air. The increased fluorescence yield, produced by red light, can be inhibited by a subsequent irradiation with far-red light. The action spectrum for the effect of far-red light shows a maximum near 705 mμ. The effects of red and far-red light on the fluorescence yield of chlorophyll a are thought to be another manifestation of the second Emerson effect.

The primary process of photosynthesis: An interpretation of the Emerson effect and of the light-induced spectral changes at 7,000 A

The Franck, and the semiconductor, theories of the primary process of photosynthesis are reviewed and discussed. In addition, an extension of the electron transfer theory of photosynthesis is presented and a new interpretation of the Emerson effect and of the light-induced spectral changes observed in algae at 7,000 A is given in terms of this extended theory.

Studies on the Second Emerson Effect in the Hill Reaction in Algal Cells

This paper shows that the "second Emerson effect"1 exists not only in photosynthesis, but also in the quinone reduction (Hill reaction), in Chlorella pyrenoidosa and Anacystis nidulans. The peaks at 650 mmu, 600 mmu, 560 mmu, 520 mmu, and 480 mmu, observed in the action spectrum of this effect in the Hill reaction in Chorella, are attributable to chlorophyll b; the occurrence of an additional peak at 670 mmu, 620 mmu, and of two (or three) peaks in the blueviolet region suggests that (at least) one form of chlorophyll a contributes to it. In analogy to suggestions made previously in the interpretation of the Emerson effect in photosynthesis, these results are taken as indicating that excitation by light preferentially absorbed by one (or two) forms of chlorophyll a (Chl a 690 + 700), needs support by simultaneous absorption of light in another form of chlorophyll a (Chl a 670)-directly or via energy transfer from chlorophyll b-in order to produce the Hill reaction with its full quantum yield. In Anacystis, the participation of phycocyanin in the Emerson effect in the Hill reaction is revealed by the occurrence, in the action spectrum of this effect, of peaks at about 560 mmu, 610 mmu, and 640 mmu; a peak at 670 mmu, due to Chl a 670, also is present.