RESUMO Reguladores de crescimento (RCs) e tipos de vedação de frascos que permitem as trocas gasosas podem favorecer o desenvolvimento de sistemas de propagação in vitro de plantas. O objetivo do presente estudo foi avaliar os efeitos da suplementação de citocinina na indução de multibrotações e a influência das trocas gasosas no desenvolvimento in vitro de microestacas de Jacaranda cuspidifolia Mart. Segmentos nodais foram cultivados em meio suplementado com diferentes concentrações (0,25; 0,5; 1,0 e 2,0 mg L-1) de 6-benziladenina (BA). No tratamento controle não houve adição de RCs. Após 30 dias de cultivo, as microestacas foram isoladas e transferidas para um meio de enraizamento suplementado com 1,0 mg L-1 de ácido indol-3-butírico. Nesta etapa, os frascos de cultura foram vedados com tampas rígidas de polipropileno com membrana porosa (1 M; 21 μL L-1 s-1 CO2) ou sem membrana (0 M; 14 μL L-1 s-1 CO2). A suplementação de citocinina induziu a ativação de gemas axilares de J. cuspidifolia. Os maiores números de gemas foram observados nos explantes cultivados na presença de 0,5 – 1,0 mg L-1 BA. As microestacas mantidas em frascos com maior nível de troca gasosa (1M) apresentaram maior porcentagem de enraizamento e maiores comprimentos de raiz e de parte aérea. A análise microscópica mostrou maior diferenciação dos tecidos foliares nas plantas mantidas em frascos com maior nível de troca gasosa (1M). Essas plantas também apresentaram maior espessura do mesofilo e consequentemente maior espessura da lâmina foliar. Os resultados obtidos fornecem novas informações para o estabelecimento de um sistema eficiente de propagação in vitro para J. cuspidifolia.

ABSTRACT Plant growth regulators (PGRs) and types of flasks sealing that allow gas exchange can favor the development of in vitro plant propagation systems. The objective of the present study was to evaluate the eff ects of cytokinin supplementation on the induction of shoot proliferation and the influence of gas exchange on the in vitro development of Jacaranda cuspidifolia Mart microcuttings. Nodal segments were cultured in medium supplemented with diff erent concentrations (0.25; 0.5; 1.0 and 2.0 mg L-1) of 6-benzyladenine (BA). In the control treatment, there was no addition of PGRs. After 30 days of culture, the microcuttings were isolated and transferred to a rooting medium supplemented with 1.0 mg L-1 indole-3-butyric acid. At this stage, the culture fl asks were sealed with rigid polypropylene lids with a porous membrane (1 M; 21 μL L-1 s-1 CO2) or with no membrane (0 M; 14 μL L-1 s-1 CO2). Cytokinin supplementation induced the activation of axillary buds of J. cuspidifolia. The highest numbers of shoots were observed in explants cultivated in the presence of 0.5–1.0 mg L-1 BA. The microcuttings kept in flasks with a higher level of gas exchange (1M) had a higher percentage of rooting and greater root and shoot lengths. Microscopic analysis showed a greater differentiation of leaf tissues in plants kept in flasks with a higher level of gas exchange (1M). These plants also showed greater mesophyll thickness and, consequently, greater leaf blade thickness. The results provide new information for establishing an efficient in vitro propagation system for J. cuspidifolia.

ABSTRACT The availability of reliable and reproducible micropropagation systems is a decisive step to successfully propagate plant species with slow growth and low germination rate. The effect was investigated of gibberellin (GA) and cytokinin (CK) in the in vitro germination and development of Dietes bicolor (Steud.) Sweet ex Klatt. Seeds were inoculated in Water + Agar; in Murashige e Skoog (MS) medium without plant growth regulators (PGRs) and in MS medium supplemented with 1 or 2 mg L-1 gibberellic acid or 6-benzylaminopurine. The germination, growth, and architecture of the plants presented significant alterations according to the treatments. Germination percentage increased at 2 mg L-1 GA. Plants grown on the GA-supplemented medium also showed larger leaves. The presence of CK in the culture medium induced the activation of axillary shoot buds and reduced the root length. CK and GA had antagonistic effects on the thickness of the leaf tissues. The activation of multiple shoots in plants cultured with CK in the medium allowed the in vitro propagation of approximately three plants per germinated seed. The results obtained in the present study bring an unprecedented description of a germination system for a higher yield in D. bicolor micropropagation.

Resumo A compreensão do comportamento in vitro de explantes de flamboyant cultivados em meio de cultura suplementado com diferentes tipos e concentrações de citocininas pode auxiliar na otimização de sistemas de regeneração estabelecidos para essa espécie vegetal. Objetivou-se com o presente estudo avaliar o comportamento de explantes cotiledonares de flamboyant quando cultivados na presença de elevadas concentrações de 6-benziladenina (BA) ou cinetina (KIN). Segmentos cotiledonares obtidos de plântulas germinadas in vitro foram inoculados em meio de cultura Murashige e Skoog (MS), suplementado com diferentes concentrações (1, 2, 4, 8 mg L-1) de 6-benziladenina (BA) ou cinetina (KIN). No tratamento controle não foi adicionado reguladores de crescimento. Após 40 dias de cultivo, independente da concentração utilizada, os tratamentos suplementados com BA apresentaram maiores porcentagens de formação de calos e massa fresca, em comparação aos tratamentos suplementados com KIN. A formação de gemas adventícias foi observada principalmente nos tratamentos suplementados com BA. Análises histológicas evidenciaram que a formação de gemas adventícias ocorreu na periferia de calos formados a partir de células do mesofilo, nas regiões de seccionamento do explante. Os resultados obtidos fornecem novas informações para o estabelecimento de um sistema de micropropagação de flamboyant, uma importante espécie arbórea ornamental.

Abstract Understanding the in vitro performance of royal poinciana explants cultured in media supplemented with different types and concentrations of cytokinins may aid in the optimization of regeneration systems established for this woody species. In the present study we evaluate the in vitro performance of royal poinciana cotyledonary explants cultured in the presence of high concentrations of 6-benzyladenine (BA) and kinetin (KIN). Cotyledonary segments obtained from in vitro germinated seedlings were inoculated in Murashige and Skoog (MS) medium, supplemented with different concentrations (1, 2, 4, 8 mg L-1) of BA or KIN. In the control treatment, no plant growth regulators (PGRs) were added. After 40 days of culture, regardless of the concentration used, the treatments supplemented with BA presented higher calli percentage and fresh mass compared to treatments supplemented with KIN. Adventitious shoots were mainly observed in BA-treatments. Histological analysis showed that adventitious shoots formed at the periphery of callus formed from mesophyll cells in the regions of the explant sectioning. The results obtained provide new information for the establishment of a micropropagation system for royal poinciana, an important ornamental tree species.