Softening-up mannan-rich cell walls

The softening and degradation of the cell wall (CW), often mannan enriched, is involved in several processes during development of higher plants, such as meristematic growth, fruit ripening, programmed cell death, and endosperm rupture upon germination. Mannans are also the predominant hemicellulosic CW polymers in many genera of green algae. The endosperm CWs of dry seeds often contain mannan polymers, sometimes in the form of galactomannans (Gal-mannans). The endo-beta-mannanases (MANs) that catalyse the random hydrolysis of the beta-linkage in the mannan backbone are one of the main hydrolytic enzymes involved in the loosening and remodelling of CWs. In germinating seeds, the softening of the endosperm seed CWs facilitates the emergence of the elongating radicle. Hydrolysis and mobilization of endosperm Gal-mannans by MANs also provides a source of nutrients for early seedling growth, since Gal-mannan, besides its structural role, serves as a storage polysaccharide. Therefore, the role of mannans and of their hydrolytic enzymes is decisive in the life cycle of seeds. This review updates and discusses the significance of mannans and MANs in seeds and explores the increasing biotechnological potential of MAN enzymes.

The 15th International Geological Congress, South Africa (1929): The Resurgence of Wegener’s Continental Drift Theory

The 15th International Geological Congress was held in South Africa in 1929. Many interesting issues were tackled, thanks to the development of geophysical techniques, ideas about magmatic differentiation, and the origin of the Karroo System, among others. The importance of the Congress from the point of view of the history of geology lies in the fact that an ‘inflection point’ occurred as regards thinking about the continental drift theory that had been proposed by Wegener a few years earlier. It can be said that the contributions of Du Toit allowed a deepening in the theoretical bases of this scientific hypothesis, which celebrated its first hundred years in 2012.

Intención y eficacia en el dibujo de la ciudad. el Concurso de Madrid de 1929

Se analiza el Concurso de anteproyectos para la urbanización y extensión de Madrid de 1929 desde un punto de vista gráfico. Tras contextualizar el proceso, se estudian los dibujos que de él se derivaron, tanto los planos de Información de la Ciudad, elaborados por los servicios municipales, como los que surgieron en la respuesta de los concursantes. Se hace especial mención de los realizados por el equipo que quedó en primer lugar, el encabezado por Zuazo y Jansen.