关键词: 杜仲, 形成层活动周期, 过氧化物酶同工酶, 酯酶同工酶

Abstract: The cambium of Eucommia ulmoides Oliv resumed its activities in mid-March. It ceased to produce new phoem cells at the end of July, but continued to differentiate into xylem cells until mid-August, at which time the cambium became dormant albeit subsequent differentiation of newly formed immature phloem and xylem cells into mature ones continued until December. In consistent with the periodicity of cambial activity, the variability of peroxidase isozyme activity as demonstrated by isozymography was most significant in the cambial region. PO I and PO II presented only in the spring when cambium activity was resumed. The activity of PO III was weakened in summer and increased gradually reaching to the highest level in winter. The variability of esterase isozyme activity in the vascular tissues was in consistent with the periodicity of cambial activity. Isozyme bands of EST III-V near the negative pole of the zymograph disappeared in specimens collected during growth season and its activity was revived when cambium became dormant. Isozymes of EST II being the most active and present over time, might play an important role in devolopment and differentiation of vascular tissues.

Key words: Eucommia ulmoides Oliv, periodicity of cambial activity, peroxidase isozyme, esterase isozyme