76-The-use-of-the-electrolyte-leak-agemethod-for-assessing-cellmembrane-stability-as-awater-stress

TheuseoftheelectrolyteleakagemethodforassessingcellmembranestabilityasawaterstresstolerancetestindurumwheatMohammedBajji,Jean-MarieKinetandStanleyLutts*LaboratoiredeCytogénétique,UniversitécatholiquedeLouvain,5(bte13)PlaceCroixduSud,B-1348,Louvain-la-Neuve,Belgium;*Authorforcorrespondence(e-mail:lutts@bota.ucl.ac.be;phone:+32-10-472037;fax:+32-10-473435)Received2January2001;acceptedinrevisedform17April2001Keywords:Cellmembraneinjury,Droughttolerance,Electrolyteleakage,Osmoticstress,Polyethyleneglycol,TriticumdurumAbstractThisworkwascarriedouttoadapttheelectrolyteleakagetechniquetodurumwheatandthentoevaluateitsrelevanceintheassessmentofthecellmembranestabilityasamechanismofwaterstresstoleranceinthisspe-cies.Themethodcurrentlyusedisbasedoninvitrodesiccationofleaftissuesbyasolutionofpolyethyleneglycol(PEG)andasubsequentmeasurementofelectrolyteleakageintodeionisedwater.Itconsistsofthreesuc-cessivesteps:(1)awashingtreatmenttoremovesolutesfrombothleafsurfacesandcellsdamagedbycutting;(2)astressperiodduringwhichtheleaftissuesareplungedinaPEG-solutionand(3)arehydrationperiodduringwhichafter-effectsofthestressareevaluated.Duringthewashingperiod,themajorpartofelectrolyteswasremovedwithin15min.Varyingthestressconditionsinfluencedboththepercentandthekineticsofelec-trolyteleakageduringrehydration.Electrolyteleakageexhibitedacharacteristicpatternreflectingtheconditionofcellularmembranes(repairandhardening).Inpractice,werecommenda15-minutewashingtime,a10-hourstressperiodand4hofrehydration.Theextentofthecellmembranedamagenotonlycorrelatedwellwiththegrowthresponsesofwheatseedlingsbelongingtovariouscultivarstowithholdingwaterbutalsowiththerec-ognisedfieldperformancesofthesecultivars.Therelativeproportionofendogenousionslostintheeffusateduringtherehydrationstepmayvarystronglyaccordingtotheelementanalysedandtheprecisenutritionalsta-tusoftheplantshouldthereforebeconsidered.However,anincreaseininorganicionleakagedoesnotfullyexplaintherecordedPEG-inducedincreaseinelectricalconductivity(EC)