ABSTRACT
To elucidate one mechanism by which putrescine (Put) functions in plant signaling under osmotic stress, Put and ABAcontents, and plasma membrane-NADPH oxidase (PM-NOX) activity were detected in wheat seedling leaves. Underosmotic stress, ABA and Put contents, PM-NOX activity, and PM-NOX-dependent O2.- production all increased. Theinhibitor tungstate (T) of ABA bio-synthesis reduced the increases in ABA and Put contents under osmotic stress. Theinhibitor D-arginine (D-Arg) of Put bio-synthesis didn’t reduce osmotic-induced increase of ABA, but it inhibited theincreases of PM-NOX activity and O2. - production, and the inhibitory effects were reversed by exogenous Put. Thesefindings suggested that ABA might regulate Put biosynthesis, and Put might regulate PM-NOX activity. Treatments withthree inhibitors imidazole (I), diphenylene iodonium (DPI) and pyridine (P) of PM-NOX reduced significantly not only O2. -production, but also the stress-induced increase of Put content, which indicated that O2. - production might regulate Putbiosynthesis. Treatments with EGTA (Ca2? chelator), La3? and verapamil (V) (Ca2? channel blockers) reduced significantly the stress-induced increase of Put content, which suggested that Ca2? might regulate Put biosynthesis. With thesefindings, it could be concluded that Put was involved in ABA signaling induced by osmotic stress via regulating PM-NOXactivity in wheat seedling leaves.