Researchers from MIT have been able to filter water using plant xylem. In tests conducted with deionised water in which bacteria and dye were introduced, the xylem filter effectively removed both when subjected to pressure.
Xylem is a transport tissue in vascular plants that conducts water and dissolved nutrients upwards from the roots. Tracheids, which are cells in the xylem, are shorter and have smaller diameters in conifers, thereby offering higher resistance to flow but a greater cross-sectional area of the stem to conducting xylem tissue. This likely makes it the most suitable xylem tissues for filtration at the micron or larger scale.
The researchers prepared the xylem filter by removing the bark of pine tree branches and then inserting it into a tube. The pressure that was used for this study suggests that it is easily achievable using a gravitational pressure head. The device construction therefore seems to be simple, considering that the wood might have to be replaced often.
While these initial results are cause for optimism, the fact remains that these tests were conducted under laboratory conditions. This filter should work with real-world water samples.