Comparative Biochemistry and Physiology, Part A 150 (2008) S51–S55

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Comparative Biochemistry and Physiology, Part A

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when they accumulate them and what they use when they experience comprising raffinose, stachyose and verbascose.

Society for Experimental Biology Annual Main Meeting6th – 10th July 2008, Marseille, France

YSAS — YOUNG SCIENTIST AWARD SESSION

YSAS.1Grow fast–die young: Exploring the growth–survival trade-offin plants

R. Atkinson (University of Sheffield)

The reasons why fast growing organisms typically ‘die young’, isa fundamental question in evolutionary ecology. There have beenmany studies across a variety of taxa, indicating that there is afundamental trade-off in resource allocation to traits which promotegrowth and those which promote maintenance and defence of theindividual, creating a ‘growth–survival’ trade-off, yet its physiologi-cal basis is largely unknown. In this study I aim to identify themechanistic basis of this trade-off and for this purpose usemonocarpic plants, which only flower and fruit once before wholeorganism senescence.

Key to understanding physiological differences between plants isknowledge of what different species store as reserve compounds,

stress (e.g. eaten by herbivores). There is very little informationavailable regarding the compounds stored by the vast majority ofplants. I am able to address this issue, due to recent advances inmetabolic profiling, by mass spectrometry. This allows a non-targetedapproach to identifying important compounds that differ between thespecies. I have analysed samples obtained from four monocarpicthistles, harvested at several points in the year, from the nutrient poorsoil at a Site of Special Scientific Interest (SSSI) in the Peak DistrictNational Park. These thistles develop large roots suggestive of storagereserves. I have extracted and analysed the metabolites in these roots,after optimising the mass spectrometry technique for detecting thestorage compounds that are present. A Principle Components Analysis(PCA) of the data (shown below) reveals that the species can beseparated by their root metabolite content. The four thistle species(indicated by colour) cluster discretely according to the PCAmodel. AnOrthogonal Partial Least Squares-discriminant analysis of potentialstorage compounds indicate that the species are distinguishable byrelative concentrations of sucrose and the raffinose series of fructans,

S52 Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S51–S55

I have used the storage compound information from this field data,in combination with a large outdoor exploratory experiment, toinvestigate storage dynamics of a range of species with very differentgrowth strategies. This experiment comprises eight species and twotreatments of one or two full defoliations in a randomised blockdesign. I have measured under-ground/above-ground biomass andstorage compounds after six harvests. I show that, by the end of thegrowth season, defoliated plants have significantly less storagebiomass available for spring re-growth and that biomass in defoliatedand control plants varies depending on species and growth rates. Isuggest that the costs of fast growth after defoliation treatmentsinclude reduced fecundity and the ‘ultimate cost’, which is death ofthe organism.

In conclusion, the growth–survival trade-off is a major andubiquitous trade-off, which explains much of the ecological and life-history variation between species. It is exciting to begin to discern themechanistic basis of this trade-off, especially due to recent advances inmetabolic profiling.

doi:10.1016/j.cbpa.2008.04.039

YSAS.2Beyond buoyancy and vision: The potential for the Root effect todeliver oxygen to tissues other than the swim bladder and eye

J.L. Rummer, C.J. Brauner (University of British Columbia)

Teleost fish possess a unique, pH-sensitive hemoglobin (Hb) that,in the presence of an acidosis, substantially reduces the affinity andcarrying capacity for O2 (Root effect). To date, this efficient O2 deliverymechanism is only known for filling a swim bladder (SB) against hugepressure gradients (N50 atm) associated with depth and foroxygenating the metabolically active, yet avascular retinal tissue ofthe eye. In spite of the clear benefits to O2 delivery for buoyancy andvision, no study has been conducted to determine whether the Rooteffect may be important in optimizing O2 delivery to other tissuessuch as muscle, which is the focus of this research.

Fig. 1. Representative trace depicting real-time changes in extracellular pHan acid induced Root effect (vertical dashed line furthest to the left), adrene(CA) induced short-circuiting (vertical line on the right) over the course o

During environmental or exercise-induced stress, blood pH mayfall; however, some fish regulate red blood cell (RBC) intracellular pH(pHi) by releasing catecholamines that activate the sodium/proton(Na+/H+) exchanger (βNHE) on the RBCmembrane. The βNHE removesH+s from the RBC resulting in an intracellular alkalosis, an increase inHb–O2 affinity, and O2 uptake at the respiratory surfaces is safe-guarded, which is the ultimate goal of this mechanism. In ourproposed model, when adrenergically stimulated blood encountersplasma-accessible carbonic anhydrase (CA), an enzyme found in theRBC but also membrane-bound and potentially plasma-accessible inselect locations, it will catalyze H+s removed from the RBC to form CO2.This CO2 will back-diffuse into the RBC creating an intracellularacidosis (extracellular alkalosis), reducing Hb–O2 affinity, and ulti-mately elevating PO2 via the Root effect. We created an in vitro closedsystem using rainbow trout (Oncorhynchus mykiss) blood where wecan (1) simulate an acid-induced Root effect, (2) adrenergicallystimulate the RBCs, and finally (3) short-circuit the βNHE via CA(CA-mediated Root effect), all of which can be monitored in real-time(Fig. 1). Data generated currently support our Hypothesis: adrenergicRBC pH regulation can be short-circuited in the presence of plasma-accessible CA, therefore generating a Root effect increase in PO2. In fact, ifthis scenario also occurs in the tissues of O. mykiss, CA-mediatedshort-circuiting of adrenergic pH regulation can facilitate an increasein PO2 over 30 times that which would be generated in vertebratespossessing only a Bohr shift! We are ready to test our model in vivo byimplanting fiber-optic O2 sensors in O. mykissmusclewhile simulatingenvironmental and exercise stress with and without CA blockers.Furthermore, even though CA is not found in general circulation, thereare membrane-bound and potentially plasma-accessible isoforms inmuscle endothelia, and research is underway to localize this enzymeto understand the relationship between location and function of theshort-circuiting.

Teleost fish, which are more numerous than all other vertebratescombined (terrestrial and aquatic), have evolved an extraordinary O2

delivery mechanism, the Root effect, that allows O2 delivery to the eyeand to the SB, thus allowing efficient buoyancy regulation, which maybe one of the most important factors responsible for the extensiveadaptive radiation in teleost fishes. Therefore, it is particularlyinteresting that the Root effect has not yet been investigated forgeneral O2 delivery. If the Root effect can also facilitate general O2

(light gray, y-axis on the left) and PO2 (black, y-axis on the right) uponrgic stimulation (middle vertical dashed line), and carbonic anhydrasef time (minutes).