Abstract
The effects of paclobutrazol, light emitting diodes (LEDs) and sucrose on inflorescence development in vitro were investigated in photoperiodically day-neutral Euphorbia millii. Paclobutrazol, a growth retardant, was mandatory to the shift from the vegetative to reproductive stage. Inflorescence development in the apical bud was observed after 21-30 days of culture on MS medium containing paclobutrazol. Different light qualities also influenced in vitro flowering of E. millii. Highest flowering percentage (90%), number of inflorescences per plantlet, percentage of mature inflorescences and early flowering (days to first bloom) were observed in fluorescent light. Among the LED treatments, red light reduced the flowering percentage, whereas blue, red plus far-red and blue plus far-red LED stimulated flowering in vitro. Sucrose concentration also influenced the growth and morphogenic patterns of in vitro plantlets. Sucrose at 5% enhanced inflorescence differentiation. The results indicate that inflorescence development of E. millii plantlets in tissue culture can serve as a potential model to study the role of paclobutrazol, LEDs and sucrose in the flowering process of a day-neutral plant that does not require external signals for flower induction. Also the technique described here can be used as an efficient method for production of early, synchronized and profuse flowering of E. millii pot plants.