EFEITO DAS XILOGLUCANAS DE SEMENTES E DERIVADOS NO CRESCIMENTO DE Arabidopsis thaliana

EFFECT OF SEED XYLOGLUCANS AND DERIVATES ON THE GROWTH OF Arabidopsis thaliana

RESUMO

Estudos realizados com xiloglucanas (XG) extraídas de sementes de Hymenaea courbaril L. (jatobá) mostraram que esse biopolímero apresenta atividade biológica, promovendo o crescimento de coleóptilos de trigo. Na micropropagação da macieira, foi mostrado que o meio de cultura contendo uma mistura de XG e ágar leva à formação de maior número de brotações com raízes e maior comprimento dessas que o meio solidificado com ágar. O objetivo do presente trabalho foi verificar o efeito da XG de sementes de jatobá coletadas em Sinop/MT (XGS) e em Cuiabá/MT (XGC) e da XGC hidrolisada com uma celulase (XGCH), além da XG de sementes de Tamarindus indica L. (XGT) coletadas na Bahia/BA, no crescimento de plântulas de Arabidopsis thaliana (L.) Heynh. cultivadas in vitro. No primeiro experimento, XGCH (0,25; 25 e 250 nM) ou XGC (0,5; 50 e 500 nM) foram acrescentadas a um meio MS ½ líquido. O segundo experimento comparou as XGs das diferentes fontes: XGC (500 nM), XGS (1200 nM) e XGT (800 nM), usando meio de cultura solidificado com 6 g.L-1 de ágar. Sementes de Arabidopsis thaliana recémgerminadas em placas de petri, durante 4-5 dias, foram colocadas nos meios de cultura com as diferentes concentrações de XGs, em sala de crescimento, para obtenção de plântulas. Quando plântulas foram cultivadas em meio de cultura líquido, houve diminuição do crescimento das raízes na presença da XGC e de XGCH na concentração mais alta e o efeito foi inverso na concentração mais baixa. Em meio de cultura semi-sólido, as XGs também inibiram o crescimento. Concluiu-se que as XGs apresentam papel biológico nas plântulas de Arabidopsis thaliana, estimulando ou inibindo o crescimento do sistema radicular e a formação de raízes laterais. Esses efeitos opostos variaram em função da espécie vegetal doadora das sementes contendo XG, do local de coleta das sementes, da forma da XG usada (hidrolisada ou não) e da sua concentração nos meios de cultura.

Palavras-chave:
atividade biológica; xiloglucana; oligossacarídeos

ABSTRACT

Studies on xyloglucan (XG) extracted from Hymenaea courbaril L. (jatoba) seeds showed that this biopolymer has biological activity that enhanced wheat coleoptiles growth. In apple tree micropropagation, the culture medium containing XG combined with agar induced a higher multiplication rate, rooting rate and root length than medium solidified with agar only. The purpose of this study was to determine the effect of XG from jatobá seeds extracted from jatoba seeds collected in Sinope/MT (XGS) and Cuiabá/MT (XGC), and from XGC hydrolysed with a cellulase (XGCH), as well from Tamarindus indica seeds (XGT) collected in Bahia/BA, on the growth of in vitro cultured Arabidopsis thaliana plantlets. In the first experiment, XGCH (0.25, 25 and 250 nM) or XGC (0.5, 50 and 500 nM) were added to a liquid half-strength MS medium. In the second experiment, XGs from several origins were compared: XGC (500 nM), XGS (1200 nM) and XGT (800 nM), using culture medium solidified with 6 g.L-1agar. Arabidopsis thaliana L. seeds germinated in Petri plates for 4 to 5 days were transferred to culture media containing the different concentrations of XGs and cultured in a growing room. When the plantlets were cultured in a liquid medium, their growth was very slow in the presence of XGC and XGCH at the highest concentration tested, and it was faster at the lowest concentration. In the semi-solid culture medium, XGs also reduced growth. It was concluded that XGs can play a biological role in Arabidopsis thaliana (L.) Heynh. plantlets, stimulating or inhibiting the root system growth and the lateral root formation. These opposite effects varied according to the plant specie that furnished the seeds containing XG, as well as the place where the seeds were collected, to the XG form used (hydrolyzed or not) and to its concentration in the culture media.

Keywords:
visgueiro; biometry; morphology; forest seed

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Datas de Publicação

• Publicação nesta coleção
  Jul-Sep 2008