(177) Evaluation of Different Factors on Regeneration of Plantlets from Embryos of Cycas revoluta Thunb

The micropropagation of Cycas revoluta Thunb. via somatic embryogenesis was tested on immature and mature embryos using 2,4-dichlorophenoxyacetic acid (2,4-D) in combination with benzyladenine (BA) or kinetin. In addition, the effect of media manipulation on the induction of adventitious buds was studied to optimize culture parameters for the regeneration of plantlets via organogenesis from mature embryos. Schenk and Hildebrandt basal medium containing six different NO3-: NH4+ ratios (from 90:10 to 65:35) and BA at 9 μm was used. The development of induced buds occurred on the medium containing the identical NO3-: NH4+ composition without growth regulators. The effects of two IBA concentrations on the rooting of elongated shoots were evaluated. The treatment of immature embryos with 2.26 μm 2,4-D and 0.44 μm BA and that of mature embryos with 0.9 μm 2,4-D and 4.40 μm BA promoted growth of embryogenic tissue followed by embryo formation that failed to develop further. Bud induction was obtained through the whole range of NO3-: NH4+ ratios tested. Small decrease in these ratios affected subsequent differentiation and growth. Adventitious shoots obtained on 70% NO3- showed two-fold increase in height and diameter compared with those regenerated on 75% NO3-. Furthermore, 7% of the former produced at the shoot base adventitious shoots that have similar morphology to offset growing at the base of mature plant. The rooting percentage of shoots was low. Considering the difficulty in achieving somatic embryogenesis, these results suggested that among micropropagation techniques organogenesis can be applicable for production of Cycas, although rooting is still the limiting factor.