Early Release of ABA from Cell Walls During Rose Petal Protoplast Isolation

During the isolation of rose petal protoplasts, two successivetransient abscisic acid (ABA) accumulations were detected whendigest medium and tissue slices were assayed simultaneously,using polyclonal antibodies raised against (+)-ABA. Late accumulation,occurring after more than 1 h of incubation, was observed, whetherenzymes were present or not, in a hyperosmotic medium. Veryearly accumulation, occurring at a maximum of 15 min after thebeginning of incubation, was observed only in the presence ofcellulolytic and pectinolytic enzymes. The ABA level could beincreased by the addition of tetcyclacis, an inhibitor of mono-oxygenaseknown to delay ABA oxidation. The need for cell wall digestingenzymes to observe this first ABA increase suggested that itwas due to a release from the cell wall. Analysis by radioimmunoassay(RIA) and high performance liquid chromatography (HPLC) showedthat ABA and another non-acidic immunoreactive compound werereleased from purified cell walls by the same enzymes. Key words: ABA, cell wall, protoplast, rose petal