Abstract
The Great Zelkova of Hirose Shrine (Zelkova serrata Makino) is considered to be about 1,000 years old and is reportedly difficult to propagate by axillary bud culture. Therefore, a new method of propagation was studied for this tree. Adventitious twigs, which grew from the trunk, were sampled in the end of October. The twigs were dipped in water, and nodal explants of the sprouts were cultured in Z medium for shoot elongation. Elongated shoots longer than 3 cm were cultured in R medium for rooting, and the remaining explants were re-cultured in the original test tubes. The shoots were cultured up to five times with a rooting rate of 63%. The shoots were maintained in darkness until the base of the shoot enlarged and showed a rooting rate of 84%. After acclimation and growth in a nursery, the plantlet survival rate was 76%. This method is effective for the preservation of natural monuments and precious trees that do not require mass propagation.
