Photoautotrophic micropropagation of Rhododendron

Photoautotrophic micropropagation (no sugar in the medium under a controlled environment) has many advantages over conventional photomixotrophic micropropagation (using sugar-containing medium), such as promoted growth and development of plantlets in vitro and enhanced percent survival ex vitro with many different plant species. Rhododendron is an important ornamental woody species, which often shows low multiplication rates and low percentages of rooting in vitro and survival ex vitro in conventional photomixotrophic micropropagation, and which could possibly benefit from photoautotrophic culture. In the present study, photoautotrophic culture was investigated during the multiplication and preparation stages of Rhododendron micropropagation. Based on the results, suitable conditions for obtaining a large number of Rhododendron plantlets with enhanced growth included the absence of plant growth regulators in the medium, a relatively high photosynthetic photon flux, a high CO ₂ concentration, two-leafed nodal cuttings as expiants and full-strength medium. Normal roots were obtained in the absence of plant growth regulators, although the percentages of rooted plantlets were low. Further research is needed to enhance rooting in photoautotrophic micropropagation.