COMPARATIVE ANATOMY AND ULTRASTRUCTURE OF ACTIVE AND DORMANT VASCULARCAMBIUM IN RHIZOME OF BOTRYCHIUM-TERNATUM

Vascular cambium of Botrychium ternatom rhizome varied according to ag e, position and season was studied by light and electron microscopy. C ambium at the 6th internode (6-year-old cambium) had the greatest numb er of active cambial cells in August and September, thus it was in the most active stage. The active cells were characterized by the presenc e of a large vacuole, few storage materials such as starch grains with in plastids or lipid droplets, a thin tangential wall; and various cel l organelles in the thin peripheral layer of cytoplasm, When the 6-yea r-old cambium reached its dormant season after November, the dormant c ells were filled with numerous storage materials and had few cell orga nelles, Our observations suggested that the initiation and cessation o f cambial activity may be correlated with the annual life cycle of thi s plant: the vegetative and reproductive leaves began to emerge in Jun e and July, respectively, and the sporophyll withered in November afte r the spore dispersal. Most cambial cells at the 10th internode, which remained in a dormant state throughout the year, were filled with num erous storage materials. Our results indicated that the activity of va scular cambium in the 10th internode was determinate.