Studies of vegetative propagation of the lychee (Litchi chinensis ...

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!< '" a: o >- :t: £5 8 a: .. U / / / / / / / ".--- -- r / / ---- /' ...- ...-,"'- W. S. Abutiate & N. Y. Nakasone (1972) Ghana Jnl agric. Sci. 5,201-211 .• ""':LvI . ~' Jr , ,~/r ' " '""Y...' •• .If
Vegetative propagation of the Iychee (Litchi chinensis Sonn.) contents. The contribution of the ray cells to the callus could also not be ascertained. Once the callus was formed, cell differentiation within it proceeded rapidly. A bridging callus from a Brewster stock 64 days after grafting is shown in Fig. 7. By the 64th day, vessels and xylem ray cells were well developed in the callus (Fig. 8). Other tissues such as sclereids (Fig. 9) developed later. The differentiation of the bridging callus into permanent tissues in lychee corroborated the findings of Mendel (1936) who observed that in citrus, the primary callus is not a transitory tissue which is destroyed but is transformed through differentiation into permanent tissue. Cambium regeneration in all the grafts occurred between the 74th and the 115th day after grafting. The determination of the exact time when the cambium differentiation started could not be ascertained due to the insufficiency of successful unions for sectioning. Within this period (74th to the 115th day) the two callus projections, one from each side of the bark (Fig. 10) grew actively and eventually met. Pith cells (Fig. 10) did not contribute to the graft union. By the 115th day the healing process was completed and the cambium regenerated (Figs 11 and 12). The extent of callus development in Kwai Mi and Brewster side-wedge grafts harvested 115 days after grafting is also shown in Figs 13, 14 and 15. In all cases callus was contributed by stock and scion but the former contributed a greater portion towards the eventual healing of the wound in the case of side-wedge grafts. In the case of approachgrafts callus contribution seemed to depend upon the cultivars used. Where a fast growing cultivar such as Brewster was approach-grafted to a slow grower such as Hak Ip, the greater contribution was made by the fast grower. Discussion The results of the various experiments showed a cultivar trend in the three subjects. A few cuttings from both girdled and non-girdled branches of Kwai Mi and Brewster from Kona and Poamoho rooted, whereas none of the Hak Ip cuttings rooted in any of the experiments. As pointed out earlier Hak Ip is the slowest grower among the three cultivars. The slow growth rate may be due to slow differentiation of tissues in the stem and Fig. 7. Transverse section through a 64-day-old callus tissue (ct) from Kwai Mi scion approach-grafted to Brewster rootstock (R) (x 38). Fig. 8. Detailed structure ofthe callus tissue (ct) from the Kwai Mi scion showing vessels (U) (X 136). Fig. 9. Further detailed structure ofthe callus tissue showing well-developed sclereids (m) (x 635). branches coupled perhaps with other factors not as yet determined. Histology of the graft union between Hak Ip and the other two cultivars also revealed the slow rate of proliferation of callus tissue, a condition which may explain the rooting failures.
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Studies of vegetative propagation of the lychee (Litchi chinensis ...

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