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This experiment was carried out to clarify seasonal changes of the rooting ability in vivo and in vitro, and to clarify relationship between rooting ability and endogenous growth substances of cuttings in herbaceous cutting of Gypsophila paniculata L. cv. Bristol Fairy. In in vivo cutting, the cuttings taken in May and September showed high rooting percentages (above 80%). Whereas the cuttings in July and August showed much lower rooting percentages, and few of the cuttings taken in October were rooted. Callus was formed at only spring cuttings, and the death rate of cuttings increased in June and July. In in vitro cutting, regardless of taking time all cuttings showed even rooting percentages ranged 67.5 to 75%. The addition of the May and July extracts to MS medium in vitro cutting, resulted in root promoting effect of the May extracts, and root inhibiting effect of the July extracts. The activities of auxin-like substances and rooting co-factors were high in spring and early summer, decreased in July and August, and increased again in September, whereas in October the activity of rooting inhibitors appeared high. The activities of endogenous auxin-like substances contained in the stem tissue were not less than those in the leaf tissue.
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