Growth regulators and guaiacol peroxidase activity during the induction phase of somatic embryogenesis in Picea species

Biochemical studies during the induction phase of somatic embryogenesis in Picea abies [L.] Karst. and P. omorika [Pančić] Purk. can supplement our basic knowledge of the developmental processes accompanying the formation of embryogenic tissues from explants. Such studies may also contribute to finding the markers specific to the early stages of somatic embryogenesis of spruce species and, consequently, to the optimization of the process of initiation of embryogenic tissues from different types of plant explants treated with various growth regulator combinations. In this paper the effect of certain growth regulator systems on enzymatic activity was studied. The analysis of guaiacol peroxidase activity (EC 1.11.1.7), based on the spectrophotometric method, showed that this activity was the lowest in mature zygotic embryos (explants) and significantly higher in 8-week-old embryogenic and non-embryogenic calluses treated with various combinations of growth regulators. In the newly initiated embryogenic tissue, the activity of this enzyme decreased and remained at a lower level during proliferation, irrespective of the applied growth regulator combination. The type and concentration of growth regulators used for the initiation and proliferation of embryogenic tissues had no statistically significant effect on peroxidase activity, although during the initiation often its increased level was observed in calluses treated with 2.4-D. Detection of guaiacol peroxidase activity in the induction phase of somatic embryogenesis proves its participation in this process. The subsequent change in its activity indicates that this peroxidase can be a biochemical marker of somatic embryogenesis of the tested spruce species.