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I'm designing an experiment where the roots of the plant will grow in a sterile environment while the shoot will grow in a non-sterile grow room. For this reason the environments of the shoot and the root should have some form of physical separation.
Is there any material that allows roots to grow through it but will stop fungi and bacteria?
I might have found a solution! Kuijken et al. (2015) first germinate seeds in a sterile eppendorf filled with agar and nutrients. They then cut off the bottom of the eppendorf and stick it through the lid of a sterile plastic jar and pad it with sterile cotton. So I guess they are using the agar as a material that is permeable to the roots and "impermeable" to bacteria and fungi.
Kuijken, R. C., Snel, J. F., Heddes, M. M., Bouwmeester, H. J., & Marcelis, L. F. (2015). The importance of a sterile rhizosphere when phenotyping for root exudation. Plant and Soil, 387(1-2), 131-142.
I suggest using an inorganic substrate (soil) and drip irrigation with a solution of 300 to 1000 ppm hydrogen peroxide. Peroxide is a well-known antiseptic and in these concentrations are not likely to damage root tissues. I do use peroxide in these concentrations for control of fungus in my garden and immerse roots in it when repotting bonsai and other potted plants. Furthermore there is a commercial broad spectrum fungicide preparation sold under the brand name Zerotol. However, all these applications, the existence of the peroxide solution on plant tissues is temporary/transient. I have not, however, used the peroxide solution as the sole source of plant water as I am suggesting, nor do I know of any studies of its use in this way.
I grow trees in Turface MVP, a high-fired montmorillonite clay and use only inorganic fertilizers, yet indigenous mycorrhiza spontaneously appears in my pots. Pumice is commonly used as a bonsai substrate used in association with organic fertilizers that are utilized only through bacterial action. This is to say that I don't think there is a solid growth substrate that is inherently antiseptic.
