SummaryDuring Arabidopsis seed development large quantities of mucilage, composed of pectins, are deposited into the apoplast underneath the outer wall of the seed coat. Upon imbibition of mature seeds, the stored mucilage expands through hydration and breaks the outer cell wall that encapsulates the whole seed. Mutant seeds carrying loss-of-function alleles of AtSBT1.7 that encodes one of 56 Arabidopsis thaliana subtilisin-like serine proteases (subtilases) do not release mucilage upon hydration. Microscopic analysis of the mutant seed coat revealed no visible structural differences compared with wild-type seeds. Weakening of the outer primary wall using cation chelators triggered mucilage release from the seed coats of mutants. However, in contrast to mature wild-type seeds, the mutant's outer cell walls did not rupture at the radial walls of the seed coat epidermal cells, but instead opened at the chalazal end of the seed, and were released in one piece. In atsbt1.7, the total rhamnose and galacturonic acid contents, representing the backbone of mucilage, remained unchanged compared with wild-type seeds. Thus, extrusion and solubility, but not the initial deposition of mucilage, are affected in atsbt1.7 mutants. AtSBT1.7 is localized in the developing seed coat, indicating a role in testa development or maturation. The altered mode of rupture of the outer seed coat wall and mucilage release indicate that AtSBT1.7 triggers the accumulation, and/or activation, of cell wall modifying enzymes necessary either for the loosening of the outer primary cell wall, or to facilitate swelling of the mucilage, as indicated by elevated pectin methylesterase activity in developing atsbt1.7 mutant seeds.
Interaction of poly(2-vinylpyridine)−poly(ethylene oxide) (P2VP-b-PEO) diblock copolymers with noble
metal compounds in aqueous media and metal nanoparticle formation in such systems were studied. In
all cases, the characteristics of the micelles filled with metal compounds strongly depend on the nature
and geometry of the metal compound, which, in turn, influences the morphology of the finally produced
metal nanoparticles. Metal compound addition induces micellization even at very low pH values, where
the P2VP-b-PEO block copolymers are dissolved molecularly. The driving force of such a micellization is
the coordination of VP units with metal ions, which proceeds by three different basic scenarios, depending
on the type of metal compound and the pH of the medium. In all the cases the P2VP-b-PEO micelles
containing metal compounds work as “nanoreactors” for metal nanoparticle formation.
Highly ordered funnel-like BaCrO 4 superstructures with a complex form and a remarkable self-similar growth pattern as well as very long BaSO 4 fiber bundles with repetitive growth patterns can be readily generated by using sodium polyacrylate as a structure directing agent in the mineralization process. The formation of fibers and fiber bundles as well as finer morphological details can be effected by variations of the temperature, pH, and concentration.
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