Research School of Biology
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Research School of Biology
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Student OpportunitiesProspective PhD Students in this group
FacilitiesFacilities within the group include staff and workshops for experimental design and making supporting equipment, as well as four (4) stable isotope mass spectrometers in the stable isotope facility. Professor’s Farquhar lab has developed analytical techniques for stable isotope research in plants (C, O and H) and is running a stable isotope facility with four isotope ratio mass spectrometers. Analysis using these machines is available on a contract basis or for cooperative research, both inside and outside ANU. Seminar SeriesA weekly seminar series is presented by group members, visitors and invited speakers. When: Every Wednesday (unless otherwise notified) (Map: http://campusmap.anu.edu.au/largemap.asp - Bldg 46, E4) Time: 4pm Contact: For more information on these seminars, contact Prof Roderick Dewar on 6125-2447 or Roderick.Dewar@anu.edu.au LATEST SEMINAR : The seminar series takes a break over July and restarts on 05 August 2009. Wednesday 26 August 2009 Speaker: Dr Thomas Lennie Functional Ecology Group, Research School of Biology
Venue: Robertson Seminar Room Discussing: The effects of solutes on the phase behaviour of phospholipid embranes Synopsis: Severe dehydration is lethal for most biological species; however, there are a number of organisms which have evolved mechanisms to avoid damage during dehydration. One of these mechanisms is the accumulation of small solutes (e.g. sugars), which have been shown to preserve membranes by inhibiting deleterious phase changes at low hydration. Specifically, sugars reduce the gel to fluid phase transition temperatures of model lipid/water mixtures. PREVIOUS SEMINARS : Wednesday 01 July 2009 Speaker: Dr John Evans Environmental Biology Group, Research School of Biology
Venue: Robertson Seminar Room Discussing: Resistances along the CO2 diffusion pathway inside leaves Synopsis: CO2 faces a series of resistances while diffusing between the substomatal cavities and the sites of carboxylation within chloroplasts. The absence of techniques to measure the resistance of individual steps makes it difficult to define their relative importance. Resistance to diffusion through intercellular airspace differs between leaves, but is usually of minor importance. Leaves with high photosynthetic capacity per unit leaf area reduce mesophyll resistance by increasing the surface area of chloroplasts exposed to intercellular airspace per unit leaf area, Sc. Cell walls impose a significant resistance and could account for more than 50% of the total resistance. Most of the remaining resistance is imposed by one or more of the three membranes as mesophyll resistance can be altered by varying the expression of cooporins. Wednesday 17 June 2009 Speaker: Prof Fred Chow Photobioenergetics Group, Research School of Biology
Discussing: Chasing the Elusive Cyclic Electron Flow in Leaf Segments Synopsis: The main function of photosynthetic membranes is to store light energy in ATP and NADPH, which are used in the ratio of 3:2 in carbon assimilation. The membranes have four protein complexes and other smaller components to perform the task. Photosystem II (PS II) splits water into oxygen, electrons and protons. The electrons flow through PS II, the cytochrome bf complex and PS I in series (linearly) to give NADPH. The protons, deposited in a reservoir (the lumen), drive nature’s tiny motor, the ATP synthase, to form ATP. Linear electron flow alone, however, does not provide a sufficient supply of ATP in the required ratio of three ATP to two NADPH molecules for carbon assimilation, let alone additional ATP for other processes such as on-going repair of inevitably-photodamaged PS II. Therefore, cyclic electron flow around PS I occurs to deposit more protons in the lumen, at an efficiency of two protons per photon, compared with 1.5 protons per photon in linear electron flow. Because no net product is formed in cyclic electron flow, quantification of the flow rate has been difficult. This talk reports on our attempt to quantify cyclic electron flow in leaf segments under varied environmental conditions, as part of a broader investigation to probe the four photosynthetic membrane protein complexes in situ in leaves. Wednesday 10 June 2009 Speaker: Dr Nikolaos Fylass School of Geography, University of Leeds, Discussing: Variation of foliage properties and plant functional types across the Amazon Basin Synopsis: We analysed 1040 individual trees, positioned in 63 plots across the Amazon Basin, for a set of biochemical and structural traits. The amount of variation attributed to the taxonomic affinity and/or the location of the tree was estimated in order to quantify the phylogenetic and the environmental influence on these characters. In general intrinsic values of most trait pairs coordinate, although different species were found to be located at discrete locations along a common axis of coordination. Additionally, growth environment was found to substantially modify inter-relationships between key traits with the environmental effect of trait variation to a large degree predictable from observed edaphic and climatic variables. A three-way ordination incorporating species traits, plot level species abundances and soil/climatic conditions will be described. This analysis not only allowed the intensity of plant trait/environment associations to be quantified (through a mutual linkage to a plot level species abundance table) but also through cluster analysis for four discrete tropical forest functional types to be identified. Wednesday 27 May 2009 Speaker: Assoc Prof Owen Atkin Functional Ecology Group, Research School of Biological Sciences Discussing: Impacts of thermal history on metablic scaling Synopsis: Using data from a wide range of biomes, a growing number of studies have shown that inter-specific variations in plant metabolic rates (e.g. photosynthesis and respiration) are linked to variations in related functional traits (e.g. tissue chemistry and/or area/mass relationships). Such studies have shown that while overall trends are held across biomes, there is also evidence that there is considerable scatter in such relationships. Given the importance of such scaling relationships for predicting shifts in vegetation patterns and changes in carbon fluxes between plants and the atmosphere, it is essential that the importance of individual climate parameters (e.g. temperature) in determining variations in functional trait scaling relationships be quantified. In this seminar, I present data on the impact of sustained changes in growth temperature on rates of respiration, photosynthesis and associated plant functional traits. The mechanisms underpinning thermal acclimation of respiration to sustained changes in growth temperature will be discussed. I show that in addition to altering the phenotype of individual plants, changes in growth temperature can alter scaling relationships used to predict rates of leaf and root respiration. This finding provides a framework via which thermal history can be better accounted for in coupled global climate-vegetation models. Wednesday 15 May 2009 Speaker: Prof Marilyn Ball Functional Ecology Group, Research School of Biological Sciences Discussing: Nitrogen fertilisation increases tree mortality under hot, dry conditions Synopsis: Field-based experiments conducted on eucalypt and mangrove species showed greater mortality of nitrogen fertilised trees when water was limiting under hot, dry conditions. Fertilising with nitrogen had no effect on hydraulic characteristics of twigs, but stimulated leaf area growth. Increasing atmospheric CO2 concentration around the eucalypts induced greater hydraulic conductance at the root/shoot junction, but the inhibition by nitrogen of root penetration into the soil led to enhanced death of the tree seedlings with the rapid onset of hot, dry weather conditions in summer. These results have far reaching implications for responses of forests to combined effects of increasing nutrient loads and climate change. Wednesday 06 May 2009 Speaker: Robert K. Niven UNSW@ADFA, Canberra Discussing: A Derivation of the Maximum Entropy Production Principle and Various Applications Synopsis: The maximum entropy principle (MaxEnt) of Jaynes is used to derive a conditional, local formulation of the "maximum entropy production'' (MEP) principle [1], which states that a flow system with variable flow(s) or gradient(s) will converge to a steady state position of maximum production of thermodynamic entropy. The analysis provides a steady state analogue of equilibrium thermodynamics, applicable to many complex flow systems including heat-induced (B'enard) convection, the Earth climate circulatory system, turbulent fluid flow, biochemical reactions and ecological systems. The analysis involves the synthesis of traditional engineering control volume analysis with a MaxEnt analysis, using a local "flux entropy" defined on the set of instantaneous fluxes through a fluid element. The analysis reveals a very different manifestation of the second law of thermodynamics in flow systems, which explains the formation of complex non-equilibrium systems, including life. Wednesday 22 April 2009 Speaker: Dr Charles Lineweaver RSES, RSAA & Planetary Scienec Institute, ANU
Discussing: Life, gravity and the second law of thermodynamics Synopsis: We review the cosmic evolution of entropy and the gravitational origin of the free energy required by life. All dissipative Wednesday 15 April 2009 Speaker: Mr Keith Schulze Environmental Group, RSBS Discussing: Evaluating the short-term regulatory effects of the ERECTA gene in Arabidopsis The ERECTA gene, known widely for its effects in the Landsberg erecta ecoptype of Arabidopsis, plays an important role in many The objective of this study is to separate those short-term direct effects of the ER gene from its long-term effects, on TE and the Wednesday 08 April 2009 Speaker: Dr Suan Chin Wong Environmental Biology Group, RSBS
Discussing: Humidity in the Intercellular Space of Leaves Does Not Saturate at High Transpiration Rate Wednesday 01 April 2009 Speaker: Ms Foteini Hassiotou University of Western Australia,
Discussing:
CO2 diffusion into sclerophylls: anatomical and physiological Wednesday 18 March 2009 Speaker: Dr Youshi Tazoe Environmental Biology Group, RSBS Discussing:
Carbon isotope discrimination and photosynthesis : Mesophyll conductance to CO2 in a C3 plant and CO2 leakiness from the bundle sheath cells in a C4 plant Measuring carbon isotope discrimination during CO2 exchange helps us to know the flow of CO2 inside leaves. In C3 plants, diffusion of CO2 into leaves is restricted not only by stomata but also by the intercellular airspaces and liquid phase into chloroplasts, which was defined as the mesophyll conductance to CO2 diffusion (gm). However, little is known on whether gm changes with respect to photon flux density (PFD) and CO2 partial pressure (pCO2). In this study, the effects of PFD and/or pCO2 on gm were examined in wheat leaves using a membrane inlet mass spectrometer. Measurements were made in 2% O2 to reduce the fractionation associated with photorespiration. In wheat, gm was independent of PFD between 200 and 1500 mmol m-2 s-1 and was independent of pCO2 between 80 and 500 mbar. In C4 plants, CO2 is concentrated around Rubisco in the bundle-sheath (BS) cells by a CO2-concentrating mechanism. Some CO2 concentrated by this mechanism leaks back to mesophyll cells or intercellular spaces and the ratio of the rate of CO2 leakage from BS cells to the rate of CO2 fixation by PEPC was defined as the CO2 leakiness (f), which has been estimated by measuring carbon isotope discrimination during CO2 exchange. Although f remains constant over a wide range of CO2 and temperatures, f shows a tendency to increase when measured at low PFDs (40-240 mmol m-2 s-1). How f increases at low PFDs is unknown. In this study, we examined the changes in f when PFD was transiently changed using Flaveria bidentis (NADP-ME type, dicot). When PFD was transiently changed from high (2000 mmol m-2 s-1) to low (300 mmol m-2 s-1), f changed quickly from 0.3 to 0.8 before decreasing to 0.5 after 90 min. When PFD was changed from low to high, f reduced from 0.5 to 0.3. Wednesday 11 March 2009 Speaker: Dr Caille Bathellier Universite de Paris-Sud, Visiting Fellow, Environmental Biology Group, RSBS Discussing:
An isotopic approach to root respiratory metabolism in French bean C3 photosynthesis discriminates against 13C so that plant organic matter is on average 13C-depleted by 20‰ compared to atmospheric CO2. However, other post-photosynthetic discriminations (e.g. during dark respiration) occur that may modify the δ13C of plant organic matter. While leaf dark respiration has been shown to produce 13C-enriched CO2, root respiration, though poorly documented, seems to produce 13C-depleted CO2. In the present study, the origin of the 13C-natural abundance in respired CO2 of intact bean roots was investigated in relation to substrate availability under continuous darkness. In contrast to leaves, root-respired CO2 is 13C-depleted as compared to sucrose, and the 13C-signal does not correlate at all with the respiratory quotient (that is, the type of respired substrates). Such an isotopic divergence between leaves and roots appears when leaves turn to autotrophy. Isotopic labeling data demonstrate that the 13C-depletion in respired CO2 is caused by both the contribution of the pentose phosphate pathway (PPP) to the CO2 efflux (22%), and the quasi-stochiometric relationship between the PDH and the Krebs cycle fluxes. Under continuous darkness, the relative PPP flux is kept constant and the consumption of (13C-depleted) lipids compensates for the decrease of the flux associated with the Krebs cycle. Such a pattern results in an invariant δ13C of respired CO2. Taken as a whole, it is concluded that, unless the 13C photosynthetic fractionation varies at the leaf level, the root 13C-signal does not change under natural environmental conditions throughout a circadian day/night cycle, thereby buffering isotopic daily variations in ecosystems. Wednesday 25 February 2009 Speaker: Mr Wee Ho Lim Environmental Biology Group, RSBS Discussing: What do climate models tell us about our water availability in the past and future? What will happen to water availability in the future? Will it remain the same or will it change? Wednesday 18 February 2009 Speaker: Dr Mark G. Tjoelker Dept of Ecosystem Science and Management, Texas A&M University Discussing: Plant respiration and temperature: Acclimation and adaptation in a warming world The temperature response of plant respiration is a fundamental relationship in the global carbon cycle. The patterns and mechanisms of short-term temperature acclimation and long-term climatic adaptation of respiration remain poorly understood, but are important in constraining respiratory carbon flux with climate warming. A plant trait-based approach using nitrogen may be useful in quantifying general predictive relationships of leaf and whole-plant respiration across diverse plant taxa and in informing the debate concerning metabolic scaling theory. Wednesday 11 February 2009 Speaker: Associate Professor William Sherwin School of Biological, Earth and Environmental Sciences, UNSW Visiting Fellow, Environmental Biology Group, RSBS Discussing:
Genes are Information – Who would have guessed? Everyone knows that genes are information, so it comes as a shock to realise that over 50 years of knowledge about the flow of computer information has rarely been applied directly to genes. We quantify genetic biodiversity using Shannon's information index. Simulations, and trials on a diverse array of species, from birds to snails to flies to trees, shows that the information approach vastly improves genetic assessment of dispersal between populations – a vital tool for conservation management. The hierarchical information approach also adapts well to analysis of variation within populations, linkage between DNA sequence elements, and other genetical and ecological tasks. Sherwin WB, Jabot F, Rush R, Rossetto M 2006 Measurement of biological information with applications from genes to landscapes Molecular Ecology 15:2857-2869. Rossetto M, Kooyman R, Sherwin WB, Jones R. 2008. Dispersal limitations, rather than bottlenecks or habitat specificity, can restrict the distribution of rare and endemic rainforest trees. Amer. J Bot 95(3): 321–329. Click here for details of other previous seminars.
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Page last updated: 28 August 2009 Please direct all enquiries to: RSB Webmaster Page Authorised by: Director, RSBS |
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