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Anatomy of Stem Hyperplasia Called Tokkuri Disease in Chamaecyparis Obtusa

Yamamoto, Fukuju, Shimizu, Shunji, Hashizume, Hayato
Chamaecyparis obtusa, bark, cambium, hyperplasia, stems, tracheids, trees, wood anatomy, Japan
The stem hyperplasia called tokkuri-disease in Japan was observed on the lower part of stems of 25-29-year-old Chamaecyparis obtusa trees. The anatomy of the hyperplastic portions was characterised by rapid proliferation of the cambium, short and thin-walled tracheids, a large number of multiseriate rays, and thickened bark. The cambial activity in the hyperplastic portion was high in July and remained high until mid-October. Transverse sections show the hyperplastic portions of the cambium and growth ring boundaries are sinuous, whereas those in non-hyperplastic portions of the same trees or in normal trees are not. The sinuosity of cambia was closely related with cambial activity. The ecological and physiological causes of stem hyperplasia are discussed on the basis of anatomical studies.