Biotechnology of the Tree Fern Cyathea smithii Hook. f. (Soft Tree Fern, Katote). I. Morphogenic Potential of Shoot Apical Dome, Plant Regeneration, and Nuclear DNA Content of Regenerants in the Presence of TDZ and NAA


 In nature, the tree fern
 Cyathea smithii
 lacks meristem multiplication; therefore, a system of vegetative propagation in vitro is required to protect the species’ gene resources. Experiments were carried out on the apical dome of
 C. smithii
 J. D. Hooker (soft tree fern, Katote) to determine its morphogenic potential using 1/2 strength of Murashige and Skoog medium containing various concentration of thidiazuron [TDZ; 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea)] (0.01, 0.1, 1.0, and 5.0 µM) supplemented with naphthalene acetic acid (0.25 µM). The success of the treatments was determined by the number of regenerants per explant, level of regenerant development, and nuclear DNA content in the green mesophyll cells. The highest number of regenerants was achieved in the presence of 5.0 µM TDZ and the lowest at 0.01 µM TDZ. The quality of development of the regenerants was expressed as the number of formed leaves and their growth per individual plantlet. The highest growth and development of regenerants occurred at the lowest concentration of TDZ (0.01 µM), and the lowest growth and development of regenerants occurred at the highest TDZ concentration (5.0 µM); however, the number of regenerants showed the opposite. In gametophytes, the nuclear DNA content ranged from 4.74–4.78 pg representing haploid level, whereas in sporophytes it ranged from 8.45–9.13 pg and was diploid. These results prove the stability of the regenerant genome after TDZ treatment of meristematic cells.