Jones, RJ, Hoegh-Guldberg, O, Larkum, AWD & Schreiber, U 1998, 'Temperature-induced bleaching of corals begins with impairment of the CO2 fixation mechanism in zooxanthellae', Plant, Cell and Environment, vol. 21, no. 12, pp. 1219-1230.
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The early effects of heat stress on the photosynthesis of symbiotic dinoflagellates (zooxanthellae) within the tissues of a reef-building coral were examined using pulse-amplitude-modulated (PAM) chlorophyll fluorescence and photorespirometry. Exposure of Stylophora pistillata to 33 and 34 °C for 4 h resulted in (1) the development of strong non-photochemical quenching (qN) of the chlorophyll fluorescence signal, (2) marked decreases in photosynthetic oxygen evolution, and (3) decreases in optimal quantum yield (F(v)/F(m)) of photosystem II (PSII). Quantum yield decreased to a greater extent on the illuminated surfaces of coral branches than on lower (shaded) surfaces, and also when high irradiance intensities were combined with elevated temperature (33 °C as opposed to 28 °C). qN collapsed in heat-stressed samples when quenching analysis was conducted in the absence of oxygen. Collectively, these observations are interpreted as the initiation of photoprotective dissipation of excess absorbed energy as heat (qN) and O2-dependent electron flow through the Mehler-Ascorbate-Peroxidase cycle (MAP-cycle) following the point at which the rate of light-driven electron transport exceeds the capacity of the Calvin cycle. A model for coral bleaching is proposed whereby the primary site of heat damage in S. pistillata is carboxylation within the Calvin cycle, as has been observed during heat damage in higher plants. Damage to PSII and a reduction in F(v)/F(m) (i.e. photoinhibition) are secondary effects following the overwhelming of photoprotective mechanisms by light. This secondary factor increases the effect of the primary variable, temperature. Potential restrictions of electron flow in heat-stressed zooxanthellae are discussed with respect to Calvin cycle enzymes and the unusual status of the dinoflagellate Rubisco. Significant features of our model are that (1) damage to PSII is not the initial step in the sequence of heat stress in zooxanthellae, and (2) light plays ...
O'Meara, TJ, De Lucca, S, Sporik, R, Graham, A & Tovey, E 1998, 'Detection of inhaled cat allergen.', Lancet (London, England), vol. 351, no. 9114, pp. 1488-1489.
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Ralph, PJ 1998, 'Photosynthetic response of laboratory-cultured Halophila ovalis to thermal stress', Marine Ecology-Progress Series, vol. 171, pp. 123-130.
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Chlorophyll a fluorescence was able to rapidly detect responses of laboratory-cultured Halophila ovalis to acute changes in temperature. Six heating (27.5, 30.0, 32.5, 35.0, 37.5 and 40.0 degrees C) and 6 chilling (10.0, 12.5, 15.0, 17.5, 20.0 and 22.5 d
Ralph, PJ 1998, 'Photosynthetic responses of Halophila ovalis (R. Br.) Hook. f. to osmotic stress', Journal Of Experimental Marine Biology And Ecology, vol. 227, no. 2, pp. 203-220.
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Chlorophyll fluorescence was used to monitor the onset, development and recovery from hyper- and hypo-osmotic stress effects of the seagrass, Halophila ovalis (R. Br.) Hook. f. H. ovalis was able to tolerate rapid transfer from normal (35 ppt) seawater t
Ralph, PJ & Burchett, M 1998, 'Impact of petrochemicals on the photosynthesis of Halophila ovalis using chlorophyll fluorescence', Marine Pollution Bulletin, vol. 36, no. 6, pp. 429-436.
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Laboratory-cultured Halophila ovalis showed tolerance to petrochemical exposure up to 1% (w/v) solution of Bass Strait crude oil, an oil dispersant (Corexit 9527) and a mixture of crude oil and dispersant, Quantum yield, as measured by chlorophyll fluore
Ralph, PJ & Burchett, M 1998, 'Photosynthetic response of Halophila ovalis to heavy metal stress', Environmental Pollution, vol. 103, no. 1, pp. 91-101.
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This paper deals with the photosynthetic effects of a range of heavy metals on the seagrass Halophila ovalis. In this study, the photosynthetic response of laboratory-cultured II. ovalis to four heavy metals (Cu, Cd, Pb, Zn) was investigated. The results
Ralph, PJ, Gademann, R & Dennison, WC 1998, 'In situ seagrass photosynthesis measured using a submersible, pulse-amplitude modulated fluorometer', Marine Biology, vol. 132, no. 3, pp. 367-373.
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Assessments of photosynthetic activity in marine plants can now be made in situ using a newly developed, submersible, pulse-amplitude modulated (PAM) fluorometer: Diving-PAM. PAM fluorometry provides a measure of chlorophyll a fluorescence using rapid-li
Ralph, PJ, Morrison, DJ & Addison, A 1998, 'A quantitative study of the patterns of morphological variation within Hormosira banksii (Turner) Decaisne (Fucales : Phaeophyta) in south-eastern Australia', Journal Of Experimental Marine Biology And Ecology, vol. 225, no. 2, pp. 285-300.
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Homzosira banksii shows a considerable degree of morphological variability throughout its range in south-eastern Australia, apparently in relation to the local habitat, and there have been several previous qualitative attempts to categorize this variatio
Razmovski, V, O'meara, T, Hjelmroos, M, Marks, G & Tovey, E 1998, 'Adhesive tapes as capturing surfaces in Burkard sampling', Grana, vol. 37, no. 5, pp. 305-310.
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Ritchie, RJ & Larkum, AWD 1998, 'Uptake of Thallium, a Toxic Heavy-Metal, in the Cyanobacterium Synechococcus R-2 (Anacystis nidulans, S. Leopoliensis) PCC 7942', Plant and Cell Physiology, vol. 39, no. 11, pp. 1156-1168.
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Uptake of the toxic heavy-metal, thallium, was studied in the cyanobacterium Synechococcus R-2 (PCC 7942) using clinically available 201Tl+. Thallium was found to distribute across the plasmalemma passively, and so the accumulation ratio of the ion ([TI+]i/[Tl+]o) could be used to calculate the apparent membrane potential (Δψi,o) of the cells (ETli,o+=Δψi,o). The permeability of the plasmalemma to Tl+ (PTl+≈1 to 5 nm s-1) is higher than that of K+. Valinomycin does not increase the permeability of Tl+. Transient changes in the Δψi,o of cells, because of electrogenic transport of ions, could be detected from its effects upon the uptake rate of Tl+. HCO3- hyperpolarized Synechococcus cells, whereas NH4+, CH3NH3+, and K+ led to depolarization. The use of Tl+ as a reporter of Δψi,o has some inherent limitations. Tl+ is toxic at very low concentrations (inhibitory effects are apparent after about 6 h at concentrations as low as 1 mmol m-3). The rate of equilibration is slow (t1/2≈5 to 20 min). Equilibration of Tl+ takes about 2 h, which limits its value as a membrane potential probe. Large amounts of Tl+ bind to the surface of the cells making the method impracticable for measuring accumulation ratios of less than about 10 (Δψi,o values smaller than about -60 mV). Cultures continuously exposed to Tl+ (10 mmol m-3) eventually become Tl+ resistant by actively extruding Tl+ (ΔμTli,o+=-3±0.2 kJ mol-1) and so thallium cannot be used as a Δψi,o probe in such cells.
Mitchell, JG, Barbara, G, Dillon, L, Pearson, L, Seymour, JR, Blackburn, N, Bergerson, B & Luchsinger, R 1998, 'Motility in marine bacteria', Australia.
Seymour, JR & Mitchell, JG 1998, 'Millimetre-scale distributions of marine bacteria.', Australia.