Abstract An efficient protocol for in vitro plant propagation of Cyrtopodium paludicolum has been developed using root tips dissected from well-developed seedlings. Root tips were cultured on Knudson medium supplemented with α-naphthaleneacetic acid (NAA), and/or thidiazuron (TDZ). TDZ did not induce protocorm-like bodies (PLBs) in the NAA absence, indicating phytoregulators synergistic effect. Medium supplemented with 1.34 μM NAA and 2.27 μM TDZ resulted in better response on PBLs, and subsequent shoot differentiation (55.25 shoots per explant), and in better rooting number and root length responses, favoring acclimatization with 90% of survived plants. However, the medium supplemented with only NAA (1.34 μM) resulted in 33.50 shoots per explant. Histological sections confirmed that only one PLB was induced per responsive root tip, and it showed numerous dispersed and extended meristemoids, or division centers that originated new PBLs. Additionally, this protocol could be an excellent model to study molecular aspects of root to shoot conversion.

A Bixa orellana L. é uma planta perene denominada urucu ou urucum, pertencente à família Bixaceae, muito utilizada na culinária, devido às suas propriedades de corante natural, cuja germinação é dificultada, devido às suas características próprias. Objetivou-se elucidar o mecanismo de dormência das sementes de urucum e avaliar o efeito de diferentes métodos para a sua quebra, aliados a diferentes temperaturas para a germinação. Os mecanismos de escarificação utilizados foram: químico (com ácido sulfúrico concentrado e etanol, em imersão por cinco minutos), físico (escarificação com lixa) e térmico (em água a 70ºC, por dois minutos, e, em seguida, sob temperaturas de 20ºC, 25ºC, 30ºC e 20-30ºC, para germinação). Avaliou-se a quantidade de água embebida pelas sementes e percentagem, primeira contagem e índice de velocidade de germinação, assim como o comprimento do hipocótilo e da raiz principal. Para as sementes que não germinaram, aplicou-se o teste de tetrazólio, para verificar a sua viabilidade. Concluiu-se que os tratamentos utilizados para a quebra da dormência não afetaram a viabilidade das sementes de urucum. Recomenda-se a escarificação com lixa ou ácido sulfúrico, por cinco minutos, e as temperaturas de 25ºC ou 20-30ºC.

Bixa orellana L. is a perennial plant known as annatto or achiote, which belongs to the Bixaceae family and is widely used in cooking, due to its properties of natural dye, whose germination is affected by its own characteristics. This study aimed at elucidating the dormancy mechanism of annatto seeds and evaluating the effect of different methods for breaking it, under different germination temperatures. The scarification methods were: chemical (with concentrated sulfuric acid and ethanol, under immersion for five minutes), physical (scarification with sand paper) and thermic (in water at 70ºC, for two minutes, and then under temperatures of 20ºC, 25ºC, 30ºC and 20-30ºC, for germination). The amount of water absorbed by seeds, and percentage, first counting and germination rate, as well as hypocotyl and taproot length, were evaluated. For the seeds that did not germinate, the tetrazolium test was applied to verify their viability. It was concluded that the treatments used for dormancy breaking did not affect the annatto seeds viability. Scarification with sand paper or sulfuric acid, for five minutes, and temperatures of 25ºC or 20-30ºC are recommended.