The transplantation shock treatment (20) involves housing at least one tree seedling (210) indoors, and exposing the tree seedlings to artificial ultraviolet light indoors prior to outdoor life. At least a portion of the incident ultraviolet light is produced by LEDs. Preferably, the artificial ultraviolet light is applied in small doses during the major part of nursing of the tree seedlings and/or during a single period in the end of an indoors nursing period. Independent claims are also included for: (1) a light device for plant treatment； and (2) a use of artificial light to treat transplantation shock in plants.
