Effect of Melatonin on the Growth of Dendrobium officinale Protocorm-Like Bodies

Dendrobium officinale Kimura & Migo is a perennial herbaceous plant of the genus Dendrobium in the family of Orchidaceae with high medicinal value. Melatonin (MT) is an indole-like tryptamine with functions such as regulating plant growth and development. This experiment investigated the effects of different concentrations of MT on the growth and development of protocorms of D. officinale protocorm-like bodies (PLBs). The results showed that the changes in morphological indicators such as color, cluster size, and surface changes were more significant under 75 mu M MT than those of 0 mu M (CK), and the appearance of white on the PLB surface was expedited, which was more conducive to the proliferation of PLBs. MT treatment of 100 mu M inhibited the differentiation of adventitious buds, and the contents of photosynthetic pigments, polysaccharides, and flavonoids were significantly increased. Moreover, as compared with CK, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in PLBs increased significantly, while the content of malondialdehyde (MDA) decreased gradually with 75 mu M or less. In conclusion, a concentration of 75 mu M melatonin can enhance the rapid propagation rate of D. officinale in vitro, providing insights into the effects of melatonin on the growth of tissue-cultured D. officinale seedlings.