摘要：Tissue recalcitrance remains a major problem limiting woody plant propagation using in vitro biotechnology methods. Increased
generation of reactive oxygen species and high phenol concentration in woody tissues are considered as the main reasons for tissue
recalcitrance in tissue culture. In this study, oxidative enzyme activity and total phenolic concentration were analyzed in vitro in both
rejuvenated and mature shoots of birch. The effect of two factors – subculture time and medium sucrose concentration – on peroxidase
and polyphenol oxidase activity, and total phenolic concentration in rejuvenated shoots were determined as possible rejuvenationaffecting
factors. The results showed that mature shoots had increased peroxidase and polyphenol oxidase activity in shoot apices and
stems but higher phenolic concentration in leaves as compared to rejuvenated shoots. Prolonged subculture time had significant effect
on peroxidase activity and polyphenol oxidase activity in shoot apices, and thus this factor did not affect maturation. However, high
sucrose concentration significantly increased total phenolic concentration in leaves and polyphenol oxidase activity in all plant parts,
thus enhancing shoot maturation and recalcitrance in vitro.
