ETHYLENE EFFECTS ON PEROXIDASES AND CELL-GROWTH PATTERNS IN PICEA-ABIES HYPOCOTYL CUTTINGS

The effect of 2-chloroethylphosphonic acid (ethrel) on cell growth pat terns and peroxidase activity (EC 1.11.1.7) and location in young Norw ay spruce cuttings (Picea abies [L.] Karst.) was investigated. The per oxidase activity in a fraction containing soluble and membrane bound e nzymes show a diurnal variation, with decreased activity during the li ght period and a corresponding increase during the following dark peri od. The decrease during the dap could to some extent be counteracted b y treatment with ethrel. It appears that ethrel affects only peroxidas es in the isolated membrane fraction, since peroxidases bound to the c ell wall were not affected by ethrel. In vitro experiments indicated t hat the hydrophobicity of soluble peroxidases was increased by treatme nt with ethylene. Cytochemical localization of peroxidase activity in differentiating tracheids revealed a clear ethrel-induced increase in the tonoplast. It appears that ethylene affects soluble peroxidases in vivo in such a way that they are directed to a more hydrophobic envir onment, like the tonoplast. Treatment with ethrel also changed the app earance of the rough endoplasmic reticulum (ER) and Golgi apparatus. D ilated ER cisternae were observed on electron micrographs, as a result of treatment with ethrel. The number of vesicles produced by the Golg i apparatus and also the amount of vesicles fusing with the plasma mem brane in secondary-wall-forming tracheids increased considerably. The results clearly indicate that the stimulatory effect of ethylene in sp ruce seedlings on lignification and cell wall formation, is due to a g eneral stimulation on both synthesis, transport and secretion of cell wall material and not on a stimulation of peroxidase activity as repor ted for other species.