Optimization of the protocorm-like body (PLB) formation of Phalaenopsis and Dendrobium hybrids was performed by determining the effects of plant growth regulators (PGRs) and different parts and division sizes of the PLB. For both genera, the base part was the best for the proliferation of PLBs, yielding the highest number of PLBs on a PGR-free medium for Phalaenopsis and medium containing 0.1μM NAA and 10.0μM BAP for Dendrobium. As regards the division size, four-division sections resulted in a higher PLB formation efficiency for Phalaenopsis, while two-division sections produced a higher PLB formation efficiency for Dendrobium. It is expected that these findings will be applicable to efficient PLB formation of other Phalaenopsis and Dendrobium orchids.

This is the first report describing the seasonal conditions affecting shoot regeneration by the chrysanthemum cv. Baeksun. The shoot regeneration from petal explants was found to be more favorable from September to December, reaching the highest values in December. In addition, the quality of the shoots was also influenced according to the season of the explant collection, where healthy and uniform plants were derived from the explants collected in December. Choosing the proper season for explant collection affected the successive plant growth parameters (i.e., plant height and fresh weight). Thus, the current results strongly suggest that season plays an important role in plant tissue culturing, which is an essential tool for micropropagation and Agro-bacterium-mediated genetic transformation studies.