Inordertodeterminetheroleofalginate-derivedoligosaccharides(ADO)indroughtstressresistanceoftomato(Ly-copersiconesculentumMiller)seedlings,theleaveswereexposedtodifferentconcentrationsofADO(0.05%,0.10%,0.20%,0.30%and0.50%)afterdroughtstresswassimulatedbyexposingtherootsto0.6molL-1PEG-6000solutionfor6h.Changesinbiomass,electrolyteleakageandmalondialdehyde(MDA),freeproline,totalsolublesugars(TSS)andabscisicacid(ABA),theenzymeactivitiesofcatalase(CAT),superoxidedismutase(SOD),peroxidase(POD)andphenylalanineammonia-lyase(PAL)weremeasuredtoinvestigatetheeffectsofADOtreatment.TheresultsshowedthatthetreatmentwithanADOconcentrationof0.20%exhibitedthehighestperformanceofdroughtstressresistanceinthetomatoseedlingsbydecreasingtheelectrolyteleakageandtheconcentrationofMDA,increasingthecontentsoffreeproline,TSSandABA,andincreasingtheactivitiesofCAT,SOD,PODandPALaftertreatmentwithADO.Itissuggestedthatchangesinelectrolyteleakage,MDA,osmoticsolutes,ABA,anti-oxidativeenzymeandPALactivitieswereresponsiblefortheincreaseddroughtstressresistanceintomatoseedlings.Toourbestknowledge,thisisthefirstreportoftheeffectofADOtreatmentonenhancingthedroughtstressresistanceoftomatoseedlings.
