Efeitos fotomorfogênicos no desenvolvimento in vitro de Bixa orellana L.

Abstract

Bixa orellana, commonly known as annatto, is a plant whose seeds are used as a source of food colorants and in traditional medicine. This study evaluated the effect of light quality on the morphophysiology of B. orellana germinated and cultivated in vitro under different WPM medium proportions and hormonal concentrations. The experiments were conducted at the Plant Tissue Culture Laboratory of the Federal University of Uberlândia. To overcome seed dormancy, four treatments were applied (sulfuric acid, gibberellic acid, a combination of both, and a control), and the seeds were cultivated on standard medium under white, blue, and red LED light. During seedling development, media containing 0%, 25%, 75%, and 100% of the standard WPM nutrient concentration were used, and chlorophyll content, root length, seedling height, and number of leaves were evaluated. Callus induction was performed using hypocotyl explants cultivated under different equimolar concentrations of cytokinin (6-benzylaminopurine) and auxins (naphthaleneacetic acid or 2,4-dichlorophenoxyacetic acid) under each light condition, with evaluations based on developmental stage, fresh and dry mass. The results indicate that sulfuric acid treatment was effective in overcoming dormancy. White light promoted better morphophysiological development of seedlings and calli, and the 100% WPM medium proved superior for photosynthetic pigment biosynthesis. The combinations of 6-benzylaminopurine and naphthaleneacetic acid were more effective in callus development. Therefore, it is concluded that light quality, medium composition, hormonal concentrations, and the method of dormancy breaking influence the in vitro cultivation of annatto.