A long-term stable and adjustable osmotic pump for small volume flow based on principles of phloem loading

An adjustable pump for microfluidics employing principles of osmoregulation analogous to those of phloem loading in plant leaves has been constructed and tested. Volume flow arises in a hollow fibre with vapour-permeable hydrophobic membrane. The fibre is connected to a source chamber filled with salt crystals and saturated salt solution. The source chamber takes up water through a relatively small membrane area and delivers saturated salt solution to one end of the capillary flow path within the hollow fibre. A stationary osmotic gradient is sustained in the hollow fibre lumen by constant input of saturated salt solution and radial osmotic water absorption. The strong temperature dependence of isothermal membrane distillation enables adjustment of the flow rate up to 20 nL/s. The pump provides pulse-free flow of any liquid with constant rate for at least 26 days without recharging the source chamber. Backpressures up to 1 bar decrease the flow rate by less than 4%. The volume delivered at a constant rate is more than 40 times larger than the volume of the source chamber. Osmoregulatory pumps of the described type may be useful for microinfusion, microdialysis and analytical microsystems

Cell wall properties of transgenic tobacco plants that express a yeast derived acid invertase in their vacuole

Transgenic tobacco plants that express a yeast derived acid invertase in their vacuole were used to analyse the effects of a modification in carbon allocation on cell wall properties and turgor pressure. Significant increases in turgor pressure, free and total acid content were detected in the transgenic lines. Cell wall neutral sugars were examined by gas chromatography and as a result the arabinose concentration was found to be significantly increased in leaf 6 of the transgenic plants. In contrast, fucose was reduced. However, the size exclusion limit of the pectin network was unaffected by the genetic manipulation