Melatonin-induced Rhizome Proliferation, Differentiation, and Rooting during Rapid Propagation of Cymbidium goeringii and Cymbidium faberi

Abstract

Melatonin plays an important role in plant resistance to stress. The role of melatonin in the propagation of plant tissue, such as rhizome proliferation, differentiation, and seedling rooting in Cymbidium species, remains unknown. In this study, we selected C. goeringii and C. faberi as experimental materials and attempted to understand the effect of melatonin on this process. We found that 1.0 μM melatonin was beneficial for rhizome proliferation of C. goeringii, with a proliferation rate of 5.52. In terms of C. faberi, the highest proliferation rate of 8.29 was observed in the medium with 0.5 μM melatonin. In proliferation, the cut rhizome of C. goeringii is more likely to cause browning phenomenon than that of C. faberi. The addition of melatonin can significantly inhibit the browning phenomenon and improve the survival rate of C. goeringii rhizome. The highest number of shoot buds per explant (3.11 after 60 days) was observed in the medium with 1.0 μM melatonin. The number of shoot buds per explant (3.28 after 60 days) was significantly higher for C. faberi in the medium with 5.0 μM melatonin than that for the control. Furthermore, culture medium incorporated with 1.0 μM of melatonin had the best comprehensive effect of seedling height and root number and length of C. goeringii. By contrast, 0.5 μM melatonin significantly promoted root elongation of C. faberi, reaching 1.77 cm, whereas it was 0.28 cm in the control. We demonstrated that melatonin in specific concentrations effectively promote rhizome proliferation, differentiation, and seedlings rooting in the rapid propagation of C. goeringii and C. faberi.