Epiphyllous buds developed on leaves of shoots derived from in vitro cultured apices of sunflower seedlings. This phenomenon was cytokinin-dependent but only occurred when the cytokinin was supplied via the cultured apices producing the leaf-bearingshoots. A 1-day exposure of apices to cytokinin was sufficient for epiphyllous bud induction, although an exposure of more than 4 days yielded maximal shoot development frequencies from these buds. Preculture of complete donor seedlings on cytokinin-supplemented media and subsequent culture of excised leaves on hormone-free medium was insufficient to induce epiphyllous bud formation. Buds became macroscopically visible after 9-11 days. At this time, epiphyllous buds consisted of a functional meristem producing true shoots which were capable of seed production. The meristems were formed by a multicellular process originating from subepidermal layers on the adaxial leaf side. The role of cytokinin and other potential factors in the induction of epiphyllous buds on sunflower leaves is discussed.
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