RESUMO
Seedlings of Brassica napus were cultivated on a slowly rotating clinostat (1 rpm) or in the vertical control for 5 d. The root growth, the cotyledonary reserves and the transport of 14C-labeled sucrose from cotyledons to root system were studied in both cultural conditions. The biomass (fresh weight) of the root system was 35% higher in the horizontally clinorotated seedlings than in the controls. This increase was correlated with a greater degradation of reserve lipids and faster accumulation of sucrose in the cotyledons. The activity of isocitrate lyase, one of the two enzymes necessary to conversion of lipids into glucids, was also greater in the cotyledons of clinorotated seedlings. The labeling distribution of 14C in the cotyledons, the hypocotyl and the root system after 30, 60 and 120 min of application of 14C-labeled sucrose on the cotyledons showed higher translocation of the cotyledonary sucrose to the root system of clinorotated seedlings. In addition, we studied the effects of clinorotation on the biomass of the excised root system (of 10 d old seedlings) cultivated in a medium containing 1% sucrose. The horizontally clinorotated root system grew more than that of the controls. These results showed that the horizontal clinorotation acted on the root system growth and provoked a higher sucrose translocation from source to sink, i.e. from cotyledons to root system.
Assuntos
Brassica/metabolismo , Gravitação , Metabolismo dos Lipídeos , Raízes de Plantas/metabolismo , Rotação , Sacarose/farmacocinética , Transporte Biológico , Biomassa , Brassica/enzimologia , Brassica/crescimento & desenvolvimento , Radioisótopos de Carbono , Clorofila/metabolismo , Cotilédone/enzimologia , Cotilédone/crescimento & desenvolvimento , Cotilédone/metabolismo , Ácidos Graxos/metabolismo , Hipocótilo/enzimologia , Hipocótilo/crescimento & desenvolvimento , Hipocótilo/metabolismo , Isocitrato Liase/metabolismo , Raízes de Plantas/enzimologia , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/enzimologia , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Simulação de Ausência de PesoRESUMO
A cytological study was performed on Maize roots (Zea mays) which were grown in space (flight Biocosmos 1985) and on control roots on earth. Two criteria were selected: cell elongation in the cortical zone in the four mm of the extremity of the root and mitotic activity of the meristem. The results show that in microgravity the length of the meristem is reduced of 1/3 and that its mitotic activity increases of about twofold comparatively to the synchronous control. In parallel the cell differentiation begin closer to the root cap junction. These results are discussed relative to the influence of gravistimulation on cell proliferation and cell differentiation in roots.
