ABSTRACT
Sharkey and Singelis (1995 ) tested a model of embarrassment focusing on strength of independent self-construal, sensitivity to evaluation, and strength of interdependent self-construal. Their findings indicated social anxiety and self-construal explained 28% of the variance in embarrassability. Separately, social anxiety contributed 5.8%, with independent and interdependent self-construal explaining 6.6 and 5.2%, respectively, thus supporting the model. Sharkey and Singelis used Modigiliani's ( 1968 ) Embarrassability Scale, which focuses on embarrassing situations. The current study repeated the analysis but measured embarrassability as a disposition on a sample of Black African (59.8%), Colored (6.1%), Asian/Indian (5.9%), and White (28.2%) first-year psychology students (139 men, 485 women) between 18 and 51 years old (M = 19.5, SD = 2.9). The three constructs together explained about 47% of dispositional embarrassability. Social anxiety explained 25% of the variance, when controlling for independent and interdependent self-construal. Sharkey and Singelis' model may be more applicable to the explanation of situational embarrassability than dispositional embarrassability.
Subject(s)
Anxiety/psychology , Models, Psychological , Personality , Self Concept , Social Behavior , Adolescent , Adult , Female , Humans , Male , Middle Aged , Social Identification , South Africa , Students/psychology , Young AdultABSTRACT
Two hypotheses-that elevated night-time temperatures due to climate warming would enforce post-fire dormancy of Proteaceae seed due to low moisture, and that periods without rain during summer would exceed desiccation periods tolerated by Proteaceae seedlings-were tested empirically. Enforced dormancy, i.e., the inability to germinate due to an environmental restraint, was tested by measuring seed germination in 11 Proteaceae species in experimental mesocosms whose soils were artificially elevated by 1.4 and 3.5 °C above ambient by far-red wavelength filtered infrared lamps. Diminished totality of germination and velocities were observed in 91 and 64%, respectively, of the Proteaceae species tested. Drought resilience was tested in one-year-old seedlings of 16 Proteaceae species by withholding water from potted plants during summer in a greenhouse. The most drought-resilient Proteaceae species displayed the lowest initial transpiration rates at field capacity, the smallest declines in transpiration rate with decreasing soil water content, and the lowest water losses by transpiration. Projected drought periods leading to the complete cessation of transpiration in all Proteaceae species greatly exceeded the number of days without rain per month during summer in the current distribution ranges of those species. It was therefore concluded that enforced seed dormancy induced by elevated night-time temperatures is the post-fire recruitment stage of Proteaceae that is most sensitive to climate warming.
Subject(s)
Adaptation, Physiological , Droughts , Hot Temperature , Plant Dormancy/physiology , Proteaceae/physiology , Seasons , Seeds/physiology , Fires , Germination , Global Warming , Proteaceae/growth & development , Rain , Seedlings/growth & development , Seedlings/physiology , Seeds/growth & development , Soil , South Africa , Stress, Physiological , WaterABSTRACT
UNLABELLED: Antimicrobial peptides such as ubiquicidin (UBI) are believed to differentiate between mammalian and bacterial or fungal cells. (99m)Tc-UBI29-41 was previously tested for detecting infection in humans using SPECT. For the present study, the UBI fragment UBI29-41 (TGRAKRRMQYNRR) was conjugated to 1,4,7-triazacyclononane-triacetic acid (NOTA), radiolabeled with (68)Ga, and investigated in a rabbit infection model. METHODS: (68)Ga was obtained from a 1.85-GBq (68)Ge/(68)Ga generator. New Zealand White rabbits were anesthetized with ketamine/medetomidine before tracer administration and placed in a clinical PET/CT scanner. (68)Ga-1,4,7-triazacyclononane-1,4,7-triacetic-acid-ubiquicidin29-41 ((68)Ga-NOTA-UBI29-41) was formulated in saline solution, and 101 ± 41 MBq were administered intravenously. The tracer distribution was studied by PET/CT imaging in animals (a) that were healthy, (b) bearing muscular Staphylococcus aureus infections and turpentine oil-induced muscular inflammations, and (c) bearing ovalbumin-induced lung inflammations. Static PET/CT imaging was performed at different time intervals up to 120 min after injection. For calculation of target-to-nontarget ratios, standardized uptake values were normalized against healthy thigh muscle, representing nontargeted tissue. RESULTS: PET/CT images of healthy animals showed predominant distribution in the kidneys, liver, and bladder; heart and spleen showed moderate, declining uptake, only. The biologic half-life in blood was 29 min. Urinary accumulation of (68)Ga-NOTA-UBI29-41 peaked at 3.8 ± 0.91 percentage injected dose per gram (%ID) at 120 min, and 88 ± 5.2 %ID was recovered in total urine. (68)Ga-NOTA-UBI29-41 imaging in (b) selectively visualized the muscular infection site and was differentiated from sterile inflammatory processes. Standardized uptake value ratios for muscles (infected/inflamed) were 2.9 ± 0.93, 2.9 ± 0.50, 3.5 ± 0.86, and 3.8 ± 0.90 at 5, 30, 60, and 90 min after injection, respectively. Rabbit lungs with asthma showed insignificant uptake. CONCLUSION: (68)Ga-NOTA-UBI29-41 was strongly localized in bacteria-infected areas and minimally detected in a sterile inflammation area in rabbit muscles. The findings propose this compound to be an excellent first-line PET/CT tracer to allow the distinguishing of infection from inflammation.
Subject(s)
Gallium Radioisotopes , Heterocyclic Compounds/chemistry , Infections/diagnostic imaging , Infections/diagnosis , Radiopharmaceuticals , Ribosomal Proteins/chemistry , Tomography, Emission-Computed, Single-Photon/methods , Animals , Antimicrobial Cationic Peptides/chemistry , Heterocyclic Compounds, 1-Ring , Inflammation , Lung/drug effects , Positron-Emission Tomography/methods , Rabbits , Staphylococcal Infections/metabolism , Tissue Distribution , Tomography, X-Ray Computed/methods , Turpentine/chemistryABSTRACT
The present study describes the behaviour of photosystem II (PSII) in Amaranthus hypochondriacus and Amaranthus hybridus under water stress conditions, assessed by the analyses of the polyphasic rise in chlorophyll a fluorescence (O-J-I-P). We determined the adaptive behaviour in relation to the regulation of the different functional and structural parameters of PSII, which was a direct and rapid response due to changes in soil water status indicated by a decrease in leaf water potential and relative water content. It allows for the identification of specific key or limiting chlorophyll fluorescence parameters which could be used to identify traits conveying tolerance. For the above partial processes of PSII function studied, it seems that A. hybridus remained the more stable upon water stress (after 17 days of withholding water), concerning the specific energy fluxes of absorption/reaction centre (ABS/RC) apparent (antenna size) and trapping/reaction centre (TR/RC) (maximum trapping flux), as well as the density of the reaction centres/cross section (RC/CS) and the phenomenological trapping flux/cross section (TR(o)/CS). It was clear that amaranth adjusts the non-photochemical (k(n)) deactivation constant of PSII and to a less extend also the photochemical (k(p)) deactivation constant by means of photoregulation, which forms the basis of the quenching of chlorophyll a fluorescence. Although drought stress caused the deactivation of RCs leading to a decrease in the density of active RCs, the plants compensated by increasing the efficiency of the conversion of trapped excitation energy to electron transport beyond Q(A) (efficiency of exciton trapping/reaction centre: ET(o)/TR(o)). Subsequent damage to PSII might be the reason for the slow, or lack of recovery, for most of the parameters measured.
Subject(s)
Amaranthus/enzymology , Photosystem II Protein Complex/metabolism , Stress, Physiological/physiology , Water , Chlorophyll/metabolism , Chlorophyll A , Spectrometry, Fluorescence , Time FactorsABSTRACT
Positive psychological characteristics and executive function are correlated with gratitude, satisfaction with life, and forgiveness. The goal of this study was to replicate these findings while examining two additional constructs, namely, hope and optimism. 113 students (25 men, 88 women) between the ages of 17 to 24 years (M = 19.4, SD = 1.5) volunteered to participate. Positive correlations between executive function and gratitude were found but mixed results were obtained for forgiveness and satisfaction with life. Hope and optimism correlated positively with executive function and hierarchical multiple regression analysis indicated that they contributed significantly to the explanation of executive functioning. Further investigation into relationships between executive functioning, its neurobiological substrates, and positive psychological attributes is recommended.
Subject(s)
Altruism , Executive Function , Personal Satisfaction , Quality of Life/psychology , Social Behavior , Aspirations, Psychological , Female , Goals , Humans , Individuality , Male , Motivation , Personality Inventory/statistics & numerical data , Psychometrics/statistics & numerical data , Students/psychology , Young AdultABSTRACT
The aim of this study was to quantify the effect of the pollutant, trifluoroacetate (TFA), on growth and photosynthesis of Phaseolus vulgaris (C(3)) and Zea mays (C(4)) in order to elucidate the physiological and biochemical basis of its inhibitory action. In whole plant studies, photosynthetic gas exchange, fast phase fluorescence kinetics and Rubisco activity were measured in parallel over a 14-day period in plants cultivated in a water culture system with NaTFA added at concentrations ranging from 0.625 to 160mgl(-1). Although initial stimulation of some photosynthetic parameters was observed at low TFA concentrations early on in the experiment, marked inhibition occurred at higher concentrations. In general Z. mays was affected more severely than P. vulgaris showing a large TFA-induced decrease in both apparent carboxylation efficiency (ACE) and in vitro Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase; EC 4.1.1.39) activity. Analysis of photosynthetic gas exchange revealed that besides constraints on mesophyll processes such as Rubisco activity, stomatal limitation also increased with increasing TFA concentration, especially in P. vulgaris. In depth analysis of the fast phase fluorescence transients pointed at TFA-induced uncoupling of the oxygen evolving complex (OEC) and inhibition of electron transport beyond Q(a) including possible constraints on the reduction of end electron acceptors of photosystem I.
Subject(s)
Carbon Dioxide/metabolism , Phaseolus/drug effects , Photosynthesis/drug effects , Plant Stomata/physiology , Ribulose-Bisphosphate Carboxylase/antagonists & inhibitors , Trifluoroacetic Acid/toxicity , Zea mays/drug effects , Electron Transport/drug effects , Electron Transport/physiology , Hydrocarbons, Fluorinated/metabolism , Oxygen/metabolism , Phaseolus/growth & development , Phaseolus/metabolism , Photosynthesis/physiology , Photosystem II Protein Complex/metabolism , Zea mays/growth & development , Zea mays/metabolismABSTRACT
Dark chilling affects growth and yield of warm-climate crops such as soybean [Glycine max (L.) Merr.]. Several studies have investigated chilling-stress effects on photosynthesis and other aspects of metabolism, but none have compared effects of whole-plant chilling (WPC; shoots and roots) with that of aboveground chilling in legumes. This is important because low root temperatures might induce additional constraints, such as inhibition of N(2) fixation, thereby aggravating chilling-stress symptoms. Effects of dark chilling on PSII, shoot growth, leaf ureide content and photosynthetic capacity were studied in two soybean genotypes, Highveld Top (chilling tolerant) and PAN809 (chilling sensitive), in experiments comparing effects of WPC with that of shoot chilling (SC). Both treatments inhibited shoot growth in PAN809 but not Highveld Top. Also, WPC in PAN809 caused a decrease in leaf ureide content followed by severe chlorosis and alterations in O-J-I-P fluorescence-rise kinetics, distinct from SC. A noteworthy difference was the appearance of a Delta K peak in the O-J-I-P fluorescence rise in response to WPC. These genotypic and treatment differences also reflected in the degree of inhibition of CO(2) assimilation rates. The appearance of a Delta K peak, coupled with growth inhibition, reduced ureide content, chlorosis and lower CO(2) assimilation rates, provides mechanistic information about how WPC might have aggravated chilling-stress symptoms in PAN809. We introduce a model explaining how chilling soil temperatures might trigger N-limitation in sensitive genotypes and how characteristic changes in O-J-I-P fluorescence-rise kinetics are linked to changes in carbon and nitrogen metabolism.
Subject(s)
Cold Temperature , Glycine max/physiology , Photosystem II Protein Complex/physiology , Soil , Carbon Dioxide/metabolism , Chlorophyll/metabolism , Darkness , Genotype , Kinetics , Photosynthesis/radiation effects , Photosystem II Protein Complex/genetics , Plant Leaves/genetics , Plant Leaves/metabolism , Plant Leaves/physiology , Plant Shoots/growth & development , Plant Shoots/metabolism , Plant Shoots/physiology , Glycine max/genetics , Glycine max/metabolismABSTRACT
In the experiments reported in this paper, we characterised the physiological and biochemical factors involved in the chilling-induced inhibition of photosynthetic carbon metabolism in soybean [Glycine max (L.) Merr.] genotypes of temperate and tropical adaptation. Plants of Maple Arrow (temperate genotype) and Java 29 (tropical genotype) were exposed to a single night at 8 degrees C. Dark chilling resulted in the inhibition of diurnal CO2 assimilation rate and decreased stomatal conductance in both genotypes. Further analysis, however, revealed a difference in the response of the two genotypes. Stomatal limitation was largely responsible for the inhibition of CO2 assimilation in Maple Arrow, whereas mesophyll limitation dominated the inhibition in Java 29. The results indicate that inhibition of stromal fructose-1,6-bisphosphatase (sFBPase; EC 3.1.3.11) activity and impaired electron transport capacity were responsible for the decrease in ribulose-1,5-bisphosphate (RuBP) regeneration capacity in Java 29. Sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity was progressively inhibited during the light period in this genotype and might impose an additional constraint on photosynthesis. Maple Arrow appears to possess, at least with respect to photosynthetic carbon metabolism, physiological and biochemical characteristics that contribute towards its superior dark chilling tolerance.
Subject(s)
Carbon Dioxide/metabolism , Carbon/metabolism , Glycine max/metabolism , Photosynthesis/physiology , Climate , Darkness , Electron Transport , Genotype , Kinetics , South Africa , Glycine max/geneticsABSTRACT
The growth stage of a soybean [Glycine max (L.) Merrill] plant may influence its physiological response to dark chilling. Opposed to vegetative development, the intense nutrient and energy requirements of the developing seeds during pod filling could cause additional chilling damage and decreased recovery capacity. Previously, we investigated dark chilling tolerance during vegetative development in two soybean genotypes, 'Maple Arrow' and 'Fiskeby V' and consistently found that photosynthesis and symbiotic nitrogen fixation (SNF) was less affected by dark chilling in 'Maple Arrow'. In this study we describe the dark chilling response of the same genotypes during pod filling. Our aim was to establish whether the potential selection criteria for dark chilling tolerance, identified during vegetative development, was equally sensitive during pod filling. The results indicate that photosynthesis is less affected by dark chilling in 'Maple Arrow' than in 'Fiskeby V', not only during vegetative development, but also during the critical reproductive stage of pod filling. 'Fiskeby V' also lacks the ability to restore normal photosynthetic capacity during an extended recovery treatment. The decrease of nodule ureide content indicates that SNF was inhibited to a similar extent in both genotypes. Nodule ureide content was reduced more than stem ureide content, suggesting that the former is a more sensitive indicator of chilling stress effects on SNF. The results indicate that certain photosynthetic and fluorescence parameters are sensitive indicators of dark chilling tolerance throughout plant development and should prove valuable in future breeding programmes aimed at increasing the chilling tolerance of soybean.
Subject(s)
Cold Temperature , Darkness , Glycine max/metabolism , Nitrogen Fixation , Symbiosis , Carbon Dioxide/metabolism , Chlorophyll/analysis , Chlorophyll A , Fluorescence , Photosynthesis , Plant Leaves/metabolism , Plant Leaves/physiology , Seeds/metabolism , Seeds/physiology , Glycine max/physiologyABSTRACT
Sub-optimal night temperatures below 15 degrees C (dark chilling) frequently reduce soybean [Glycine max (L.) Merrill] production. Nitrate application is known to alleviate some of the negative effects of low root zone temperatures, probably by counteracting the inhibition caused by decreased symbiotic nitrogen fixation (SNF). Under field conditions, however, dark chilling is frequently not accompanied by low root zone temperatures. The possibility that nitrate might increase dark-chilling tolerance under these conditions is still largely unexplored. In addition to quantifying vegetative development by means of the plastochron index, O-J-I-P (O-I(1)-I(2)-P) chlorophyll a fluorescence transients were recorded in soybean genotypes of contrasting chilling tolerance during and following exposure to dark chilling in the absence of low root zone temperatures. Plants, inoculated with the N(2)-fixing bacteria, Bradyrhizobium japonicum, were grown with and without nitrate supplementation. The recorded O-J-I-P chlorophyll a fluorescence transients were analysed by the so-called JIP-test which translates stress-induced alterations in these transients to changes in biophysical parameters that quantifies the energy flow through photosystem II (PSII). One of these parameters, the performance index (PI(ABS)), combines the three main functional steps (light energy absorption, excitation energy trapping, and conversion of excitation energy to electron transport) of photosynthetic activity by a PSII reaction centre complex into a single multiparametric expression. By using the PI(ABS) we could convincingly show that nitrate supplementation considerably enhances dark-chilling tolerance and recovery capacity of plants in the absence of low root zone temperatures. This was especially true for the chilling-sensitive genotype ('Java 29'), suggesting that the response of SNF to dark chilling might be an important factor contributing towards genotypic differences in chilling tolerance. Our results corroborated previous reports about the superior chilling tolerance of 'Maple Arrow', a chilling-tolerant genotype. The results obtained indicated that the PI(ABS) is a far more sensitive indicator of dark-chilling stress than the maximum quantum yield of primary photochemistry (F(V)/F(M)).
ABSTRACT
The effects of dark chilling on CO2 assimilation, chlorophyll a fluorescence kinetics and nitrogen fixation were compared in two Glycine max (L.) Merr. genotypes. The aim was to elucidate the mechanisms by which photosynthesis was inhibited as well as identification of selection criteria for dark chilling tolerance. Seedlings were dark chilled (8 degrees C) for 9 consecutive nights but kept at normal day temperatures (28 degrees C). CO2 gas exchange analysis indicated that photosynthesis in Maple Arrow was inhibited largely as a result of stomatal limitation, while in Fiskeby V, it indicated inhibition of the mesophyll reactions. Increased intercellular CO2 concentration and decreased carboxylation efficiency suggested loss of Rubisco activity in Fiskeby V, although no effect on the KM (CO2) of Rubisco was observed. Quantification and deconvolution of the Chl a fluorescence transients into several phenomenological and biophysical parameters (JIP-test) revealed large genotypic differences in the response of PSII to dark chilling. These parameters differentially changed in the two genotypes during the progression of the chilling treatment. Among them, the performance index, reflecting several responses of the photochemical apparatus, provided the best preliminary overall assessment of the genotypes. In contrast, the quantum yield of primary photochemistry varphiPo (FV/FM) was quite insensitive. The recovery of most of the JIP-test parameters in Maple Arrow after 6 and 9 nights of dark chilling was a major genotypic difference. Genotypic differences were also observed with regard to the ureide response and N2 fixation appeared to be more sensitive to dark chilling than CO2 assimilation. The JIP-test provided information consistent with results derived from CO2 assimilation and N2 fixation studies suggesting that it can substitute the much more time-consuming methods for the detection of chilling stress and can well satisfy the requirements of a rapid and accurate screening method.