SEM OBSERVATIONS ON 'TAWARA-SHIBO' (A SERIES OF SWELLINGS ALONG THE AXIS) STEMS OF CHAMAECYPARIS OBTUSA

The anatomy of tawara-shibo stems of Chamaecyparis obtusa (Siebold & Zucc.) Endl. was observed using a scanning electron microscope (SEM) and a light microscope. Tawara-shibo is a strange stem form with a series of swellings that appear at regular intervals along the stem axis. Multiseriate rays, trabeculae and related structures, and modified tracheids were frequently observed at swollen portions. These features were less frequent at non-swollen portions. We conclude that abnormal cambial activities, occurring at regular longitudinal intervals, cause the formation and development of these three anatomical features and higher growth rates at swollen portions. As a result of differences in growth rate between swollen and non-swollen portions, the stem form of tawara-shibo develops. It is suggested that formation of the characteristics observed in tawara-shibo stems is genetically controlled by hormonal secretion into or within the cambium.