DNA amplification in Cymbidium protocorms in vitro, as it relates to cytodifferentiation and hormone treatment

Abstract

As was shown in recently published work (Nagl, 1972b; Nagl et al., 1972) differentiation of protocorms of the orchid Cymbidium is accompanied by endomitotic nuclear cycles and by DNA amplication. The present report specifies the kind of cells and the period of development in which extra replications do occur. It is also shown that treatment with growth regulators and inhibitors of nucleic acid synthesis, which all are known to change cytodifferentiation, cause characteristic alterations in the 3H-thymidine labelling index and the mitotic index. We assume, therefore, that changes at the level of the nuclear cycle might play an important role in the differentiation of the protocorms.