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  • Author or Editor: Hisajiro Yukinaga x
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Microshoots of Japanese persimmon (Diospyros kaki L. cv. Jiro) were rooted in vitro. The roots were excised and cultured on solidified Murashige and Skoog medium. After 20 days of culture, adventitious shoots formed spontaneously and directly from the roots. Of all the tested cytokinins, 10–5 m zeatin in combination with 10–8 m IAA was the most effective in stimulating production of adventitious shoots. CPPU and 2iP also were effective cytokinins. Addition of a high concentration of auxin, especially 2,4-D, to the medium inhibited adventitious shoot formation. The percentage of root segments forming adventitious shoots increased with increasing segment length. Almost all of the longest roots (4 to 6 cm) formed adventitious shoots. Chemical names used: 6-benzyladenine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); indole-3-acetic acid (IAA); 2-isopentenyladenine (2iP); N-phenyl-N′-(2-chloro-4-pyridyl)urea (CPPU).

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When cultured in vitro, roots of four Japanese persimmon (Diospyros kaki L.) cultivars formed adventitious shoots on MS medium with 10 μm zeatin and 0.01 μm indole-3-acetic acid, although their organogenetic capacities varied. Histological study revealed that the origin of the adventitious shoots was the pericycle. The regenerated shoots grew well on the shoot proliferation medium (MS with 5 μm zeatin). Final rooting percentages of shoots regenerated from roots of three of the four cultivars were greater than those of shoots that originated from shoot tips and that had been subcultured >50 times. Shoots regenerated from `Jiro' roots rooted 10 days earlier, had more roots than those from shoot tips, and maintained higher rooting ability over ten subcultures. Rooted `Hiratanenashi' shoots regenerated from roots survived better after acclimatization than those from shoot tips. No obvious variants were observed either in vitro or in the field. The trees regenerated from roots flowered within 4 years. These findings suggest that partial rather than true rejuvenation was responsible for both the early flowering and the juvenile characteristics, i.e., the enhanced rooting ability, observed in the regenerated plants. Chemical name used: 6-(4-hydroxy-3-methylbut-2-enylamino) purine (zeatin).

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Growth of micropropagated Japanese persimmon trees (Diospyros kaki L. cv. Nishimurawase) during the initial 3 years after field establishment was compared with that of grafted trees on seedling stocks. Judging from the mean length of annual shoots per tree and the yearly increases in height, trunk diameter, and top and root dry mass, the grafted trees on seedling stocks grew poorly during the first and second growing seasons, while micropropagated trees, raised in an outdoor nursery, developed poorly only during the first growing season. In contrast, micropropagated trees raised in pots fared well soon after field establishment. These trees had more fine than middle and large roots; in contrast, grafted trees on seedling stocks had one large taproot, which died back to some extent after field establishment, with few fine roots.

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