Tailoring confocal microscopy for real-time analysis of photosynthesis at single-cell resolution.

Photoautotrophs' environmental responses have been extensively studied at the organism and ecosystem level. However, less is known about their photosynthesis at the single-cell level. This information is needed to understand photosynthetic acclimation processes, as light changes as it penetrates cells, layers of cells, or organs. Furthermore, cells within the same tissue may behave differently, being at different developmental/physiological stages. Here, we describe an approach for single-cell and subcellular photophysiology based on the customization of confocal microscopy to assess chlorophyll fluorescence quenching by the saturation pulse method. We exploit this setup to (1) reassess the specialization of photosynthetic activities in developing tissues of non-vascular plants; (2) identify a specific subpopulation of phytoplankton cells in marine photosymbiosis, which consolidate energetic connections with their hosts; and (3) examine the link between light penetration and photoprotection responses inside the different tissues that constitute a plant leaf anatomy.

Diversity climate, trust, and turnover intentions: A multilevel dynamic system.

Past research on employee trust and diversity climate is cross-sectional and often overlooks the distinction between overall unit climate and individual perceptions of climate. The current article addresses the complex relationship between trust and diversity climate, including directionality, evolution over time, multilevel characteristics, and influence on the critical outcome of turnover intentions. Using a novel, a multilevel analysis of cross-lagged panel data with latent interactions, we examined 6 years of data from 3,218 faculty members across 294 departments in a large U.S. university. We then (a) separated within-department and between-department diversity climate perceptions, (b) examined the directionality and durability of the relationships among trust and diversity climate perceptions, and (c) examined employee turnover intentions as an outcome of the trust/diversity climate perception feedback process that we identified. Results revealed a reciprocal relationship between within-department diversity climate and trust. These relationships continued over the full 6-year period and, as hypothesized, were stronger in departments with more unsupportive diversity climates. When all three variables were modeled at both levels of analysis, an influence on future turnover intentions was observed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Moving beyond unwise replication practices: The case of romantic motivation.

Replication research holds an increasingly important place in modern psychological science. If such work is to improve the state of knowledge rather than add confusion, however, replication attempts must be held to high standards of rigor. As an example of how replication attempts can add confusion rather than clarity, we consider an article by Shanks and colleagues (2015). They conducted a meta-analysis of studies examining romantic motivation, using problematic criteria for the inclusion of effects and reached conclusions of a null effect that were unwarranted. A more rigorous and defensible approach, relying on a representative analysis of effects and p-curves, suggests a different, more positive conclusion with no evidence of p-hacking. Shanks et al. also conducted several experiments that suffered from numerous issues, such as relying on inappropriate subject samples (e.g., older adults likely to be less sensitive to mating manipulations than college students used in previous research), altered research methods, and demonstrably weak manipulations, among other problems. We discuss the broader implications of this case, to illustrate both the opportunities and the pitfalls inherent in attempts to replicate contextually sensitive research. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Too drained to help: a resource depletion perspective on daily interpersonal citizenship behaviors.

This article explores the role of within-person fluctuations in employees' daily surface acting and subsequent personal energy resources in the performance of organizational citizenship behaviors directed toward other individuals in the workplace (OCBI). Drawing on ego depletion theory (Muraven & Baumeister, 2000), we develop a resource-based model in which surface acting is negatively associated with daily OCBIs through the depletion of resources manifested in end-of-day exhaustion. Further integrating ego depletion theory, we consider the role of employees' baseline personal resource pool, as indicated by chronic exhaustion, as a critical between-person moderator of these within-person relationships. Using an experience-sampling methodology to test this model, we found that surface acting was indirectly related to coworker ratings of OCBI through the experience of exhaustion. We further found that chronic levels of exhaustion exacerbated the influence of surface acting on employees' end-of-day exhaustion. These findings demonstrate the importance of employees' regulatory resource pool for combating depletion and maintaining important work behaviors. Implications for theory and practice are discussed.

Fertile and selectively flirty: women's behavior toward men changes across the ovulatory cycle.

Past research shows that men respond to women differently depending on where women are in their ovulatory cycle. But what leads men to treat ovulating women differently? We propose that the ovulatory cycle alters women's flirting behavior. We tested this hypothesis in an experiment in which women interacted with different types of men at different points in their cycle. Results revealed that women in the ovulatory phase reported more interest in men who had purported markers of genetic fitness as short-term mates, but not as long-term mates. Furthermore, behavioral ratings of the interactions indicated that women displayed more flirting behaviors when they were at high than at low fertility. Importantly, fertile women flirted more only when interacting with men who had genetic-fitness markers, not with other men. In summary, fertility not only alters women's behavior but does so in a context-dependent way that follows adaptive logic.

Affect spin and the emotion regulation process at work.

Regulating emotions is one of the most depleting activities that customer service employees are asked to do, but not all employees get burned out by the end of an emotionally laborious day. In the current study, affect spin-the trait variability of an individual's affective states-was hypothesized to increase strain and fatigue associated with emotion regulation, yet weaken the relation between recent strain and immediate fatigue. The authors examined these hypotheses in an experience sampling study of restaurant servers. Sixty-three servers completed surveys on 4 occasions during each of approximately 10 shifts (2,051 total surveys). Multilevel analyses supported the underlying model linking emotion regulation to fatigue at work as well as the hypothesized role of affect spin. Although affect spin reflects greater reactivity to affective events, it also provides some degree of a buffer from the fatiguing effects of these events.

Peacocks, Porsches, and Thorstein Veblen: conspicuous consumption as a sexual signaling system.

Conspicuous consumption is a form of economic behavior in which self-presentational concerns override desires to obtain goods at bargain prices. Showy spending may be a social signal directed at potential mates. We investigated such signals by examining (a) which individuals send them, (b) which contexts trigger them, and (c) how observers interpret them. Three experiments demonstrated that conspicuous consumption is driven by men who are following a lower investment (vs. higher investment) mating strategy and is triggered specifically by short-term (vs. long-term) mating motives. A fourth experiment showed that observers interpret such signals accurately, with women perceiving men who conspicuously consume as being interested in short-term mating. Furthermore, conspicuous purchasing enhanced men's desirability as a short-term (but not as a long-term) mate. Overall, these findings suggest that flaunting status-linked goods to potential mates is not simply about displaying economic resources. Instead, conspicuous consumption appears to be part of a more precise signaling system focused on short-term mating. These findings contribute to an emerging literature on human life-history strategies.

Service without a smile: comparing the consequences of neutral and positive display rules.

We used an experimental design to examine the intrapersonal and interpersonal processes through which neutral display rules, compared to positive display rules, influence objective task performance of poll workers and ratings provided by survey respondents of the poll workers. Student participants (N = 140) were trained to adhere to 1 of the 2 display rule conditions while delivering opinion surveys to potential patrons of an organization during a 40-min period. Results showed that, compared to positive display rules, neutral display rules resulted in less task persistence and greater avoidance behavior. These effects were mediated through a greater use of expression suppression. In addition, neutral display rules resulted in less positive respondent mood, which accounted for lower ratings of service quality and of overall favorability attitudes toward the sponsoring organization. The importance and ubiquity of neutral display rules are discussed, given the potential for positive and negative consequences at work.

A new setup for in vivo fluorescence imaging of photosynthetic activity.

Here, we describe a new imaging setup able to assess in vivo photosynthetic activity. The system specifically measures time-resolved chlorophyll fluorescence in response to light. It is composed of a fast digital camera equipped with a wide-angle lens for the analysis of samples up to 10 x 10 cm, i.e. entire plants or petri dishes. In the choice of CCD, we have opted for a 12-bits high frame rate [150 fps (frames per second)] at the expense of definition (640 x 480 pixels). Although the choice of digital camera is always a compromise between these two related features, we have designed a flexible system allowing the fast sampling of images (down to 100 micros) with a maximum spatial resolution. This image readout system, synchronized with actinic light and saturating pulses, allows a precise determination of F(0) and F(M), which is required to monitor PSII activity. This new imaging system, together with image processing techniques, is useful to investigate the heterogeneity of photosynthetic activity within leaves or to screen large numbers of unicellular algal mutant colonies to identify those with subtle changes in photosynthetic electron flow.

Personality predictors of extreme response style.

Extreme response style (ERS) refers to the tendency to overuse the endpoints of Likert-type scales. This study examined the extent to which ERS is accounted for by measures of personality, specifically, intolerance of ambiguity, simplistic thinking, and decisiveness. One hundred and sixteen pairs of undergraduate students and one of their respective peers completed a battery of questionnaires assessing these personality measures, alongside three measures of extreme responding. Results indicate that peer ratings of intolerance of ambiguity and simplistic thinking interact with the primary participant's time spent on the survey to predict the primary participant's extreme responding. Thus, those who quickly complete surveys and are intolerant of ambiguity or are simplistic thinkers are most likely to exhibit ERS. These results have implications not only for surveys using rating scales, but also illustrate how epistemic personality factors more generally influence the processing of new information.

Perceptions of obesity across the lifespan.

OBJECTIVE: Previous research on obesity stereotyping has almost extensively involved looking at the perceptions that 5-21-year-old individuals have toward members of their own age in-group. Very little research has examined how people perceive obesity across the lifespan. The current research begins to address this gap by examining the extent to which individuals between 18 and 77 years of age stereotype obesity in 20, 40, and 60-year-old targets. METHODS AND PROCEDURES: A total of 106 male and 102 female white participants viewed nine standardized Adobe- cropped photos that depicted 20, 40, and 60-year-old faces on slender, large, and very large-sized bodies. After viewing each photo, participants evaluated the targets on six dimensions used in previous obesity stereotyping research. RESULTS: As predicted, heavier women were rated more negatively than thinner women on every dimension we examined. In addition, older women were rated more negatively than younger women on attractiveness, but more positively on every other dimension. Other main effects revealed that female (relative to male) and older (relative to younger) participants were more lenient in their ratings. Several two-way interactions revealed that the obesity stereotype for attractiveness is exaggerated when targets are younger, that males (compared to females) levy a greater penalty for increasing weight, and that this pattern is exaggerated more for younger men. DISCUSSION: This research shows a consistency across the lifespan in the extent to which participants, varying in weight, age, and sex, stereotype obesity. It also appears that, at least with respect to attractiveness, younger obese individuals are denigrated to a larger degree than older. In sum, this research shows prevalent and consistent patterns of obesity stereotyping across the lifespan.

An original adaptation of photosynthesis in the marine green alga Ostreococcus.

Adaptation of photosynthesis in marine environment has been examined in two strains of the green, picoeukaryote Ostreococcus: OTH95, a surface/high-light strain, and RCC809, a deep-sea/low-light strain. Differences between the two strains include changes in the light-harvesting capacity, which is lower in OTH95, and in the photoprotection capacity, which is enhanced in OTH95. Furthermore, RCC809 has a reduced maximum rate of O(2) evolution, which is limited by its decreased photosystem I (PSI) level, a possible adaptation to Fe limitation in the open oceans. This decrease is, however, accompanied by a substantial rerouting of the electron flow to establish an H(2)O-to-H(2)O cycle, involving PSII and a potential plastid plastoquinol terminal oxidase. This pathway bypasses electron transfer through the cytochrome b(6)f complex and allows the pumping of "extra" protons into the thylakoid lumen. By promoting the generation of a large DeltapH, it facilitates ATP synthesis and nonphotochemical quenching when RCC809 cells are exposed to excess excitation energy. We propose that the diversion of electrons to oxygen downstream of PSII, but before PSI, reflects a common and compulsory strategy in marine phytoplankton to bypass the constraints imposed by light and/or nutrient limitation and allow successful colonization of the open-ocean marine environment.

On the advantages of using green light to study fluorescence yield changes in leaves.

In photosynthetic chains, the kinetics of fluorescence yield depends on the photochemical rates at the level of both Photosystem I and II and thus on the absorption cross section of the photosynthetic units as well as on the coupling between light harvesting complexes and photosynthetic traps. A new set-up is described which, at variance with the commonly used set-ups, uses of a weakly absorbed light source (light-emitting diodes with maximum output at 520 nm) to excite the photosynthetic electron chain and probe the resulting fluorescence yield changes and their time course. This approach optimizes the homogeneity of the exciting light throughout the leaf and we show that this homogeneity narrows the distribution of the photochemical rates. Although the exciting light is weakly absorbed, the possibility to tune the intensity of the light emitting diodes allows one to reach photochemical rates ranging from 10(4) s(-1) to 0.25 s(-1) rendering experimentally accessible different functional regimes. The variations of the fluorescence yield induced by the photosynthetic activity are qualitatively and quantitatively discussed. When illuminating dark-adapted leaves by a weak light, the kinetics of fluorescence changes displays a pronounced plateau which precedes the fluorescence increase reflecting the full reduction of the plastoquinone pool. We ascribe this plateau to the time delay needed to reduce the photosystem I electron acceptors.

Pocket-sized psychology studies: exploring daily diary software for palm pilots.

Daily dairies, also known as experience sampling methods (ESM) or everyday experience methods, are a common methodology utilized to provide insight into momentary psychological processes. Traditionally, such studies often have utilized paper-and-pencil surveys administered several times each day over a span of several days or weeks. However, advances in technology now allow these studies to be conducted using palmtop computers (i.e., personal digital assistants; PDAs). Three software packages for running these studies on the Palm operating system were explored and compared on a number of features Specifically, ESP (Experience Sampling Program, by Feldman Barrett & Barrett, 2001), iESP Version 3.2 (Intel Experience Sampling Program, by Intel Research Seattle & the University of Washington Computer Science and Engineering Department), and PMAT Version 2.0 (Purdue Momentary Assessment Tool, by the Military Family Research Institute at Purdue University) were examined, with their key features compared. These advances in software for running diary studies include a number of features that provide researchers with methods and information previously unavailable in diary studies and may expand the range of possibilities in diary study designs.

Episodic processes in emotional labor: perceptions of affective delivery and regulation strategies.

This study examined emotional labor processes from a within-person, episodic framework. The authors hypothesized that the influence of negative emotions on affective delivery would be lessened by regulation strategies for supervisor perceptions but not self-perceptions. In addition, difficulty maintaining display rules was hypothesized to mediate the relation between negative emotions and self-perceptions of affective delivery. Finally, the influence of surface acting strategies on these processes as well as correlations with individual differences was investigated. Hypotheses were tested using ecological momentary assessment of a sample of cheerleading instructors. Results suggest that surface actors can regulate emotions effectively on an episode-to-episode basis but find the episode more difficult. In addition, surface actors exhibit more general tendencies to devalue themselves and experience fewer positive emotions.

An episodic process model of affective influences on performance.

In this article, the authors present a model linking immediate affective experiences to within-person performance. First, the authors define a time structure for performance (the performance episode) that is commensurate with the dynamic nature of affect. Next, the authors examine the core cognitive and regulatory processes that determine performance for 1 person during any particular episode. Third, the authors describe how various emotions and moods influence the intermediary performance processes, thereby affecting performance. In the final section of the article, the authors discuss limitations, future research directions, and practical implications for their episodic process model of affect and performance.

Optimizing principal components analysis of event-related potentials: matrix type, factor loading weighting, extraction, and rotations.

OBJECTIVE: Given conflicting recommendations in the literature, this report seeks to present a standard protocol for applying principal components analysis (PCA) to event-related potential (ERP) datasets. METHODS: The effects of a covariance versus a correlation matrix, Kaiser normalization vs. covariance loadings, truncated versus unrestricted solutions, and Varimax versus Promax rotations were tested on 100 simulation datasets. Also, whether the effects of these parameters are mediated by component size was examined. RESULTS: Parameters were evaluated according to time course reconstruction, source localization results, and misallocation of ANOVA effects. Correlation matrices resulted in dramatic misallocation of variance. The Promax rotation yielded much more accurate results than Varimax rotation. Covariance loadings were inferior to Kaiser Normalization and unweighted loadings. CONCLUSIONS: Based on the current simulation of two components, the evidence supports the use of a covariance matrix, Kaiser normalization, and Promax rotation. When these parameters are used, unrestricted solutions did not materially improve the results. We argue against their use. Results also suggest that optimized PCA procedures can measurably improve source localization results. SIGNIFICANCE: Continued development of PCA procedures can improve the results when PCA is applied to ERP datasets.

Biochemical and biophysical characterization of photosystem I from phytoene desaturase and zeta-carotene desaturase deletion mutants of Synechocystis Sp. PCC 6803: evidence for PsaA- and PsaB-side electron transport in cyanobacteria.

In photosystem I, oxidation of reduced acceptor A(1)(-) through iron-sulfur cluster F(X) is biphasic with half-times of approximately 5-30 ns ("fast" phase) and approximately 150-300 ns ("slow" phase). Whether these biphasic kinetics reflect unidirectional electron transfer, involving only the PsaA-side phylloquinone or bi-directional electron transfer, involving both the PsaA- and PsaB-side phylloquinones, has been the source of some controversy. Brettel (Brettel, K. (1988) FEBS Lett. 239, 93-98) and Joliot and Joliot (Joliot, P., and Joliot, A. (1999) Biochemistry 38, 11130-11136) have attributed to nearby carotenoids electrochromic band shifts, accompanying A(1) reduction, centered at approximately 450 and 500-510 nm. As a test of these assignments, we separately deleted in Synechocystis sp. PCC 6803 the genes that encode phytoene desaturase (encoded by crtP (pds)) and zeta-carotene desaturase (encoded by crtQ (zds)). The pds(-) and zds(-) strains synthesize phytoene and zeta-carotene, respectively, both of which absorb to shorter wavelength than beta-carotene. Compared with wild type, the mutant A(1)(-) (FeS) - A(1)(FeS)(-) difference spectra, measured in cells and photosystem I complexes, retain the electrochromic band shift centered at 450 nm but show a complete loss of the electrochromic band shifts centered at 500-510 nm. Thus, the latter clearly arise from beta-carotene. In the wild type, the electrochromic band shift of the slow phase (centered at 500 nm) is shifted by 6 nm to the blue compared with the fast phase (centered at 506 nm). Thus, the carotenoid pigments acting as electrochromic markers during the fast and slow phases of A(1)(-) oxidation are different, indicating the involvement of both the PsaA- and the PsaB-side phylloquinones in photosystem I electron transport.

Cyclic electron flow under saturating excitation of dark-adapted Arabidopsis leaves.

The rate of cyclic electron flow measured in dark-adapted leaves under aerobic conditions submitted to a saturating illumination has been performed by the analysis of the transmembrane potential changes induced by a light to dark transfer. Using a new highly sensitive spectrophotometric technique, a rate of the cyclic flow of approximately 130 s(-1) has been measured in the presence or absence of 3-(3,4-dichloro-phenyl)-1,1-dimethylurea (DCMU). This value is approximately 1.5 times larger than that previously reported [Proc. Natl. Acad. Sci. U. S. A. 99 (2001) 10209]. We have characterized in the presence or absence of DCMU charge recombination process (t(1/2) approximately 60 micros) that involves P(700)(+) and very likely the reduced form of the iron sulfur acceptor F(X). This led to conclude that, under saturating illumination, the PSI centers involved in the cyclic pathway have most of the iron sulfur acceptors F(A) and F(B) reduced. In the proposed mechanism, electrons are transferred from a ferredoxin bound to a site localized on the stromal side of the cytochrome b(6)f complex to the Q(i) site. Two possible models of the organization of the membrane complexes are discussed, in which the cyclic and linear electron transfer chains are isolated one from the other.

Cohesion and performance in groups: a meta-analytic clarification of construct relations.

Previous meta-analytic examinations of group cohesion and performance have focused primarily on contextual factors. This study examined issues relevant to applied researchers by providing a more detailed analysis of the criterion domain. In addition, the authors reinvestigated the role of components of cohesion using more modern meta-analytic methods and in light of different types of performance criteria. The results of the authors' meta-analyses revealed stronger correlations between cohesion and performance when performance was defined as behavior (as opposed to outcome), when it was assessed with efficiency measures (as opposed to effectiveness measures), and as patterns of team workflow became more intensive. In addition, and in contrast to B. Mullen and C. Copper's (1994) meta-analysis, the 3 main components of cohesion were independently related to the various performance domains. Implications for organizations and future research on cohesion and performance are discussed.