1
|
Ortega-Jimenez VM, Badger M, Wang H, Dudley R. Into rude air: hummingbird flight performance in variable aerial environments. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0387. [PMID: 27528777 DOI: 10.1098/rstb.2015.0387] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/07/2016] [Indexed: 11/12/2022] Open
Abstract
Hummingbirds are well known for their ability to sustain hovering flight, but many other remarkable features of manoeuvrability characterize the more than 330 species of trochilid. Most research on hummingbird flight has been focused on either forward flight or hovering in otherwise non-perturbed air. In nature, however, hummingbirds fly through and must compensate for substantial environmental perturbation, including heavy rain, unpredictable updraughts and turbulent eddies. Here, we review recent studies on hummingbirds flying within challenging aerial environments, and discuss both the direct and indirect effects of unsteady environmental flows such as rain and von Kármán vortex streets. Both perturbation intensity and the spatio-temporal scale of disturbance (expressed with respect to characteristic body size) will influence mechanical responses of volant taxa. Most features of hummingbird manoeuvrability remain undescribed, as do evolutionary patterns of flight-related adaptation within the lineage. Trochilid flight performance under natural conditions far exceeds that of microair vehicles at similar scales, and the group as a whole presents many research opportunities for understanding aerial manoeuvrability.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'.
Collapse
Affiliation(s)
| | - M Badger
- Integrative Biology, University of California, Berkeley, CA, USA
| | - H Wang
- College of Astronautics, Nanjing University of Aeronautics and Astronautics, People's Republic of China
| | - R Dudley
- Integrative Biology, University of California, Berkeley, CA, USA Smithsonian Tropical Research Institute, Balboa, Panama
| |
Collapse
|
2
|
South PF, Walker BJ, Cavanagh AP, Rolland V, Badger M, Ort DR. Bile Acid Sodium Symporter BASS6 Can Transport Glycolate and Is Involved in Photorespiratory Metabolism in Arabidopsis thaliana. Plant Cell 2017; 29:808-823. [PMID: 28351992 PMCID: PMC5435425 DOI: 10.1105/tpc.16.00775] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 02/08/2017] [Accepted: 03/28/2017] [Indexed: 05/19/2023]
Abstract
Photorespiration is an energy-intensive process that recycles 2-phosphoglycolate, a toxic product of the Rubisco oxygenation reaction. The photorespiratory pathway is highly compartmentalized, involving the chloroplast, peroxisome, cytosol, and mitochondria. Though the soluble enzymes involved in photorespiration are well characterized, very few membrane transporters involved in photorespiration have been identified to date. In this work, Arabidopsis thaliana plants containing a T-DNA disruption of the bile acid sodium symporter BASS6 show decreased photosynthesis and slower growth under ambient, but not elevated CO2 Exogenous expression of BASS6 complemented this photorespiration mutant phenotype. In addition, metabolite analysis and genetic complementation of glycolate transport in yeast showed that BASS6 was capable of glycolate transport. This is consistent with its involvement in the photorespiratory export of glycolate from Arabidopsis chloroplasts. An Arabidopsis double knockout line of both BASS6 and the glycolate/glycerate transporter PLGG1 (bass6, plgg1) showed an additive growth defect, an increase in glycolate accumulation, and reductions in photosynthetic rates compared with either single mutant. Our data indicate that BASS6 and PLGG1 partner in glycolate export from the chloroplast, whereas PLGG1 alone accounts for the import of glycerate. BASS6 and PLGG1 therefore balance the export of two glycolate molecules with the import of one glycerate molecule during photorespiration.
Collapse
Affiliation(s)
- Paul F South
- Global Change and Photosynthesis Research Unit, U.S. Department of Agriculture/Agricultural Research Service, Urbana, Illinois 61801
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801
| | - Berkley J Walker
- Global Change and Photosynthesis Research Unit, U.S. Department of Agriculture/Agricultural Research Service, Urbana, Illinois 61801
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801
| | - Amanda P Cavanagh
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801
| | - Vivien Rolland
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra ACT 0200, Australia
| | - Murray Badger
- Australian Research Council Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra ACT 0200, Australia
| | - Donald R Ort
- Global Change and Photosynthesis Research Unit, U.S. Department of Agriculture/Agricultural Research Service, Urbana, Illinois 61801
- Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801
- Department of Plant Biology, University of Illinois, Urbana, Illinois 61801
| |
Collapse
|
3
|
Rungrat T, Awlia M, Brown T, Cheng R, Sirault X, Fajkus J, Trtilek M, Furbank B, Badger M, Tester M, Pogson BJ, Borevitz JO, Wilson P. Using Phenomic Analysis of Photosynthetic Function for Abiotic Stress Response Gene Discovery. Arabidopsis Book 2016; 14:e0185. [PMID: 27695390 PMCID: PMC5042155 DOI: 10.1199/tab.0185] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Monitoring the photosynthetic performance of plants is a major key to understanding how plants adapt to their growth conditions. Stress tolerance traits have a high genetic complexity as plants are constantly, and unavoidably, exposed to numerous stress factors, which limits their growth rates in the natural environment. Arabidopsis thaliana, with its broad genetic diversity and wide climatic range, has been shown to successfully adapt to stressful conditions to ensure the completion of its life cycle. As a result, A. thaliana has become a robust and renowned plant model system for studying natural variation and conducting gene discovery studies. Genome wide association studies (GWAS) in restructured populations combining natural and recombinant lines is a particularly effective way to identify the genetic basis of complex traits. As most abiotic stresses affect photosynthetic activity, chlorophyll fluorescence measurements are a potential phenotyping technique for monitoring plant performance under stress conditions. This review focuses on the use of chlorophyll fluorescence as a tool to study genetic variation underlying the stress tolerance responses to abiotic stress in A. thaliana.
Collapse
Affiliation(s)
- Tepsuda Rungrat
- ARC Centre of Excellence for Plant Energy Biology, Australian National University, Australia
| | - Mariam Awlia
- ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Australia
| | - Tim Brown
- ARC Centre of Excellence for Plant Energy Biology, Australian National University, Australia
| | - Riyan Cheng
- ARC Centre of Excellence for Plant Energy Biology, Australian National University, Australia
| | - Xavier Sirault
- High Resolution Plant Phenomics Centre, CSIRO Agriculture, Australia
| | - Jiri Fajkus
- Photon Systems Instruments (PSI), Czech Republic
| | | | - Bob Furbank
- ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Australia
- High Resolution Plant Phenomics Centre, CSIRO Agriculture, Australia
| | - Murray Badger
- ARC Centre of Excellence for Translational Photosynthesis, Australian National University, Australia
| | - Mark Tester
- King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Barry J Pogson
- ARC Centre of Excellence for Plant Energy Biology, Australian National University, Australia
| | - Justin O Borevitz
- ARC Centre of Excellence for Plant Energy Biology, Australian National University, Australia
| | - Pip Wilson
- ARC Centre of Excellence for Plant Energy Biology, Australian National University, Australia
| |
Collapse
|
4
|
Brown TB, Cheng R, Sirault XRR, Rungrat T, Murray KD, Trtilek M, Furbank RT, Badger M, Pogson BJ, Borevitz JO. TraitCapture: genomic and environment modelling of plant phenomic data. Curr Opin Plant Biol 2014; 18:73-9. [PMID: 24646691 DOI: 10.1016/j.pbi.2014.02.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 02/04/2014] [Accepted: 02/09/2014] [Indexed: 05/18/2023]
Abstract
Agriculture requires a second green revolution to provide increased food, fodder, fiber, fuel and soil fertility for a growing population while being more resilient to extreme weather on finite land, water, and nutrient resources. Advances in phenomics, genomics and environmental control/sensing can now be used to directly select yield and resilience traits from large collections of germplasm if software can integrate among the technologies. Traits could be Captured throughout development and across environments from multi-dimensional phenotypes, by applying Genome Wide Association Studies (GWAS) to identify causal genes and background variation and functional structural plant models (FSPMs) to predict plant growth and reproduction in target environments. TraitCapture should be applicable to both controlled and field environments and would allow breeders to simulate regional variety trials to pre-select for increased productivity under challenging environments.
Collapse
Affiliation(s)
- Tim B Brown
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia
| | - Riyan Cheng
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia
| | - Xavier R R Sirault
- High Resolution Plant Phenomics Centre, Plant Industry, CSIRO, Australia
| | - Tepsuda Rungrat
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia
| | - Kevin D Murray
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia
| | - Martin Trtilek
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia; High Resolution Plant Phenomics Centre, Plant Industry, CSIRO, Australia; Photon Systems Instruments, Czech Republic; ARC Centre of Excellence in Plant Energy Biology, Australia
| | - Robert T Furbank
- High Resolution Plant Phenomics Centre, Plant Industry, CSIRO, Australia
| | - Murray Badger
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia; ARC Centre of Excellence in Plant Energy Biology, Australia
| | - Barry J Pogson
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia; ARC Centre of Excellence in Plant Energy Biology, Australia
| | - Justin O Borevitz
- Division of Plant Sciences, Research School of Biology, Australian National University, Australia.
| |
Collapse
|
5
|
Tcherkez GGB, Bathellier C, Stuart-Williams H, Whitney S, Gout E, Bligny R, Badger M, Farquhar GD. D2O Solvent Isotope Effects Suggest Uniform Energy Barriers in Ribulose-1,5-bisphosphate Carboxylase/Oxygenase Catalysis. Biochemistry 2013; 52:869-77. [DOI: 10.1021/bi300933u] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Guillaume G. B. Tcherkez
- Institut de Biologie des Plantes,
CNRS UMR 8618, Université Paris-Sud 11, 91405 Orsay cedex, France
- Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris,
France
| | - Camille Bathellier
- Institut de Biologie des Plantes,
CNRS UMR 8618, Université Paris-Sud 11, 91405 Orsay cedex, France
- Research School of
Biology, Australian National University, Canberra ACT 0200,
Australia
| | - Hilary Stuart-Williams
- Research School of
Biology, Australian National University, Canberra ACT 0200,
Australia
| | - Spencer Whitney
- Research School of
Biology, Australian National University, Canberra ACT 0200,
Australia
| | - Elisabeth Gout
- Laboratoire de
Physiologie Cellulaire
Végétale, CEA-Grenoble, 17
rue des Martyrs, 38009 Grenoble cedex, France
| | - Richard Bligny
- Laboratoire de
Physiologie Cellulaire
Végétale, CEA-Grenoble, 17
rue des Martyrs, 38009 Grenoble cedex, France
| | - Murray Badger
- Research School of
Biology, Australian National University, Canberra ACT 0200,
Australia
| | - Graham D. Farquhar
- Research School of
Biology, Australian National University, Canberra ACT 0200,
Australia
| |
Collapse
|
6
|
Buxton L, Badger M, Ralph P. EFFECTS OF MODERATE HEAT STRESS AND DISSOLVED INORGANIC CARBON CONCENTRATION ON PHOTOSYNTHESIS AND RESPIRATION OF SYMBIODINIUM SP. (DINOPHYCEAE) IN CULTURE AND IN SYMBIOSIS(1). J Phycol 2009; 45:357-365. [PMID: 27033814 DOI: 10.1111/j.1529-8817.2009.00659.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The influence of temperature and inorganic carbon (Ci ) concentration on photosynthesis was examined in whole corals and samples of cultured symbiotic dinoflagellates (Symbiodinium sp.) using combined measurements from a membrane inlet mass spectrometer and chl a fluorometer. In whole corals, O2 production at 26°C was significantly limited at Ci concentrations below ambient seawater (∼2.2 mM). Further additions of Ci up to ∼10 mM caused no further stimulation of oxygenic photosynthesis. Following exposure to 30°C (2 d), net oxygen production decreased significantly in whole corals, as a result of reduced production of photosynthetically derived oxygen rather than increased host consumption. Whole corals maintained a rate of oxygen evolution around eight times lower than cultured Symbiodinium sp. at inorganic carbon concentrations <2 mM, but cultures displayed greater levels of photoinhibition following heat treatment (30°C, 2 d). Whole corals and cultured zooxanthellae differed considerably in their responses to Ci concentration and moderate heat stress, demonstrating that cultured Symbiodinium make an incongruous model for those in hospite. Reduced net oxygen evolution, in whole corals, under conditions of low Ci (<2 mM) has been interpreted in terms of possible sink limitation leading to increased nonphotochemical energy dissipation. The advantages of combined measurement of net gas exchange and fluorometry offered by this method are discussed.
Collapse
Affiliation(s)
- Lucy Buxton
- Department of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, AustraliaARC Centre of Excellence in Plant Energy Biology, Molecular Plant Physiology Group, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory, AustraliaDepartment of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Murray Badger
- Department of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, AustraliaARC Centre of Excellence in Plant Energy Biology, Molecular Plant Physiology Group, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory, AustraliaDepartment of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Peter Ralph
- Department of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, AustraliaARC Centre of Excellence in Plant Energy Biology, Molecular Plant Physiology Group, Research School of Biological Sciences, The Australian National University, Canberra, Australian Capital Territory, AustraliaDepartment of Environmental Sciences, Institute for Water and Environmental Resource Management, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| |
Collapse
|
7
|
de Longevialle AF, Hendrickson L, Taylor NL, Delannoy E, Lurin C, Badger M, Millar AH, Small I. The pentatricopeptide repeat gene OTP51 with two LAGLIDADG motifs is required for the cis-splicing of plastid ycf3 intron 2 in Arabidopsis thaliana. Plant J 2008; 56:157-68. [PMID: 18557832 DOI: 10.1111/j.1365-313x.2008.03581.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Summary The Arabidopsis thaliana chloroplast contains 20 group-II introns in its genome, and seven known splicing factors are required for the splicing of overlapping subsets of 19 of them. We describe an additional protein (OTP51) that specifically promotes the splicing of the only group-II intron for which no splicing factor has been described previously. This protein is a pentatricopeptide repeat (PPR) protein containing two LAGLIDADG motifs found in group-I intron maturases in other organisms. Amino acids thought to be important for the homing endonuclease activity of other LAGLIDADG proteins are missing in this protein, but the amino acids described to be important for maturase activity are conserved. OTP51 is absolutely required for the splicing of ycf3 intron 2, and also influences the splicing of several other group-IIa introns. Loss of OTP51 has far-reaching consequences for photosystem-I and photosystem-II assembly, and for the photosynthetic fluorescence characteristics of mutant plants.
Collapse
Affiliation(s)
- Andéol Falcon de Longevialle
- Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009 WA, Australia
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Takahashi S, Bauwe H, Badger M. Impairment of the photorespiratory pathway accelerates photoinhibition of photosystem II by suppression of repair but not acceleration of damage processes in Arabidopsis. Plant Physiol 2007; 144:487-94. [PMID: 17400706 PMCID: PMC1913796 DOI: 10.1104/pp.107.097253] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Oxygenation of ribulose-1,5-bisphosphate catalyzed by Rubisco produces glycolate-2-P. The photorespiratory pathway, which consists of photorespiratory carbon and nitrogen cycles, metabolizes glycolate-2-P to the Calvin cycle intermediate glycerate-3-P and is proposed to be important for avoiding photoinhibition of photosystem II (PSII), especially in C3 plants. We show here that mutants of Arabidopsis (Arabidopsis thaliana) with impairment of ferredoxin-dependent glutamate synthase, serine hydroxymethyltransferase, glutamate/malate transporter, and glycerate kinase had accelerated photoinhibition of PSII by suppression of the repair of photodamaged PSII and not acceleration of the photodamage to PSII. We found that suppression of the repair process was attributable to inhibition of the synthesis of the D1 protein at the level of translation. Our results suggest that the photorespiratory pathway helps avoid inhibition of the synthesis of the D1 protein, which is important for the repair of photodamaged PSII upon interruption of the Calvin cycle.
Collapse
Affiliation(s)
- Shunichi Takahashi
- Molecular Plant Physiology Group and Australian Research Council Centre of Excellence in Plant Energy Biology, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia.
| | | | | |
Collapse
|
9
|
Abstract
Cyanobacteria, algae, aquatic angiosperms and higher plants have all developed their own unique versions of photosynthetic CO(2) concentrating mechanisms (CCMs) to aid Rubisco in efficient CO(2) capture. An important aspect of all CCMs is the critical roles that the specialised location and function that various carbonic anhydrase enzymes play in the overall process, participating the interconversion of CO(2) and HCO(3) (-) species both inside and outside the cell. This review examines what we currently understand about the nature of the carbonic anhydrase enzymes, their localisation and roles in the various CCMs that have been studied in detail.
Collapse
Affiliation(s)
- Murray Badger
- Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, P.O. Box 475, Canberra, ACT, 2601, Australia,
| |
Collapse
|
10
|
Eichelmann H, Price D, Badger M, Laisk A. Photosynthetic parameters of leaves of wild type and Cyt b6/f deficient transgenic tobacco studied by CO2 uptake and transmittance at 800 nm. Plant Cell Physiol 2000; 41:432-9. [PMID: 10845456 DOI: 10.1093/pcp/41.4.432] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Parallel measurements of CO2 assimilation and 800 nm transmission were carried out on intact leaves of wild type and cytochrome b6/f deficient transgenic tobacco grown at different light intensities and temperatures, with the aim to diagnose rate-limiting processes in photosynthesis and investigate their adaptations to growth conditions. Maximum CO2- and light-saturated photosynthetic rate, mesophyll conductance, assimilatory charge and specific carboxylation efficiency were determined from CO2 fixation measurements and postillumination P700 rereduction time constant was measured from the transient of the 800 nm signal. Results show that growth conditions continue to modulate the expression of genes in transgenic plants, interfering with the antisense modulation, but under all environmental conditions the antisense treatment to decrease Cyt b6/f complexes ensured that the control of electron/proton transport rate by proton backpressure on the PSI donor side was stronger than the control by electron backpressure on the PSI acceptor side. Coordinated control of gene expression and enzyme activation ensures that different parts of the photosynthetic machinery--components of the electron transport chain, ribulose-1,5-bisphosphate carboxylase/oxygenase, enzymes of the sucrose and starch synthesis chains-are synthesized more or less proportionally under different environmental conditions and in case of mild genetic interference.
Collapse
Affiliation(s)
- H Eichelmann
- Tartu Ulikooli Molekulaar- ja Rakubioloogia Instituut, Estonia
| | | | | | | |
Collapse
|
11
|
Flexas J, Badger M, Chow WS, Medrano H, Osmond CB. Analysis of the relative increase in photosynthetic O(2) uptake when photosynthesis in grapevine leaves is inhibited following low night temperatures and/or water stress. Plant Physiol 1999; 121:675-84. [PMID: 10517860 PMCID: PMC59431 DOI: 10.1104/pp.121.2.675] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/1999] [Accepted: 07/06/1999] [Indexed: 05/18/2023]
Abstract
We found similarities between the effects of low night temperatures (5 degrees C-10 degrees C) and slowly imposed water stress on photosynthesis in grapevine (Vitis vinifera L.) leaves. Exposure of plants growing outdoors to successive chilling nights caused light- and CO(2)-saturated photosynthetic O(2) evolution to decline to zero within 5 d. Plants recovered after four warm nights. These photosynthetic responses were confirmed in potted plants, even when roots were heated. The inhibitory effects of chilling were greater after a period of illumination, probably because transpiration induced higher water deficit. Stomatal closure only accounted for part of the inhibition of photosynthesis. Fluorescence measurements showed no evidence of photoinhibition, but nonphotochemical quenching increased in stressed plants. The most characteristic response to both stresses was an increase in the ratio of electron transport to net O(2) evolution, even at high external CO(2) concentrations. Oxygen isotope exchange revealed that this imbalance was due to increased O(2) uptake, which probably has two components: photorespiration and the Mehler reaction. Chilling- and drought-induced water stress enhanced both O(2) uptake processes, and both processes maintained relatively high rates of electron flow as CO(2) exchange approached zero in stressed leaves. Presumably, high electron transport associated with O(2) uptake processes also maintained a high DeltapH, thus affording photoprotection.
Collapse
Affiliation(s)
- J Flexas
- Molecular Plant Physiology and Photobioenergetics Groups, Research School of Biological Sciences, Institute of Advanced Studies, Australian National University, Box 475, Canberra, Australian Capital Territory 2601, Australia
| | | | | | | | | |
Collapse
|
12
|
Messinger J, Badger M, Wydrzynski T. Detection of one slowly exchanging substrate water molecule in the S3 state of photosystem II. Proc Natl Acad Sci U S A 1995; 92:3209-13. [PMID: 11607525 PMCID: PMC42135 DOI: 10.1073/pnas.92.8.3209] [Citation(s) in RCA: 183] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The exchangeability of the substrate water molecules at the catalytic site of water oxidation in photosystem II has been probed by isotope-exchange measurements using mass spectrometric detection of flash-induced oxygen evolution. A stirred sample chamber was constructed to reduce the lag time between injection of H2(18)O and the detecting flash by a factor of more than 1000 compared to the original experiments by R. Radmer and O. Ollinger [(1986) FEBS Lett. 195, 285-289]. Our data show that there is a slow (t1/2 approximately 500 ms, 10 degrees C) and a fast (t1/2 <25 ms, 10 degrees C) exchanging substrate water molecule in the S3 state of photosystem II. The slow exchange is coupled with an activation energy of about 75 kJ/mol and is discussed in terms of a terminal manganese oxo ligand, while the faster exchanging substrate molecule may represent a water molecule not directly bound to the manganese center.
Collapse
Affiliation(s)
- J Messinger
- Research School of Biological Sciences, Australian National University, Canberra, Australia
| | | | | |
Collapse
|
13
|
Abstract
We examined 10 common indicators of social isolation and assessed which, if any, are related to subjective well-being among elderly individuals. The quantitative measures (no daily contact and minimal weekly contact), no children, having no children plus being unmarried, and having no children plus living alone, were unrelated to either global happiness or life satisfaction. The combined indicators of living alone and being unmarried as well as single indicators of having no companions or having no confidants were related at the bivariate level to both measures of well-being. When controlling for demographic, economic, and health factors, having no confidants and no companions were significantly and independently related to subjective well-being. These findings suggest that practitioners who seek information on living arrangements or marital status as proxy measures of lower psychological well-being are utilizing the wrong predictors.
Collapse
Affiliation(s)
- N L Chappell
- Centre on Aging, University of Manitoba, Winnipeg
| | | |
Collapse
|
14
|
Chappell NL, Strain LA, Badger M. Self-care in health and in illness. Compr Gerontol B 1988; 2:92-101. [PMID: 3228802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
This paper focuses on self-care, both expectations and actual behaviours, as health behaviour and as illness behaviour among a random sample of elderly individuals living in the community in a Canadian city (n = 743). The conceptualization of both health and illness behaviour follows Mechanic's (1,2) definition of illness behaviour as selective, interpretive, and evaluative. The data reveal a gap between intentions and behaviours, with elderly individuals de-emphasizing the importance of self-care and overemphasizing the importance of professional contact in their intentions compared with their behaviours. Further, self-care as health and as illness behaviour are uncorrelated with one another. Virtually all individuals engage in some health maintenance behaviours. Approximately two-thirds engage in self-care or do nothing as an initial response to common ailments. While different correlates emerge for each, health beliefs are significantly related, irrespective of whether it is health or illness behaviour.
Collapse
Affiliation(s)
- N L Chappell
- Centre on Aging, University of Manitoba, Winnipeg, Canada
| | | | | |
Collapse
|