Tissue cultures of Alternanthera brasiliana (L.) Kuntze were treated with different growth regulators (Kinetin and 2,4-D), tyrosine and Ultraviolet A radiation (UV-A; 320 - 400 nm) to investigate their effects on development and pigment production. Nodal segments of plantlets grown from seeds were inoculated in all tested media and different light conditions. After eight weeks, this material was used to evaluate biomass, chlorophyll and betacyanin production. The Murashige and Skoog (MS) + kinetin medium resulted in development of approximately four shoots/explant. This medium plus white light was the best combination for micropropagation with the highest rooting percentage and betacyanin production. Plantlets grown under UV-A illumination reduced biomass accumulation and worse Chlorophyll a / Chlorophyll b ratio. Addition of 2,4-D resulted in inhibition of pigment production and growth of plantlets.