Abstract
Variation in plant cells and tissues subcultured repeatedly in an artificial medium has been reported on many occasions. A well known case is the ‘habituation’' (GAUTHRET, 1955) of tissues which was caused by means of subculture in a medium containing a low concentration of auxin so that they became able to grow without the exbgenous auxin which had originally been required. In recent years, through repeated subculture on the same nutrient medium, several kinds of cfone have been obtained which differ from the original cultures in pigmentation, form, growth rate, and nutrient requirements (ARYA et al., 1962 ; Fox, 1963 ; STEWARD, 1963 ; BLAKELY et al., 1964 ; MURASHIGE et al., 1964). Also, the variation of totipotency in cultured tissues during the process of subculture has been reported. For example, a loss in the ability of the cultures to regenerate adventive buds and roots has been recognized (SKOOG et al., 1948 ; MURAS}IIGE et al., 1964). These kinds of variation in cultures are important problems that should be duly considered when the technique of tissue culture is being used. This paper reports the nature of the variation of totipotency in cultured tissues originated from carrot roots. In this experiment, it is also confirmed that the potency of regeneration in cultures dwindles to zero in the process of subculture, and that, on the other hand, there are hereditary differences in the totipotency of individual carrot roots.
