STANDARDIZATION OF PLANT MICROPROPAGATION BY USAGE OF A LIQUID MEDIUM WITH POLYURETHANE FOAM PLUGS OR A SOLIDIFIED MEDIUM WITH THE GELLAN GUM GELRITE INSTEAD OF AGAR

Media solidified with the gellan gum Gelrite, e.g. 0.15–0.25% always showed better growth than media with a purified quality of agar, e.g. 0.60 – 1.0%.

Use of selected, elastic polyurethane foam qualities as plugs, - without any pretreatment -, e.g. Greiner "15/17", allowed comparable or better growth than media with purified agar (0.60%). Pu foam plugs with liquid media (10ml, like solid media) seemed to have a lower buffer capacity. The pH was 0.5–1 more acid after growth as compared with agar 0.6% or Gelrite 0.2%.

Pu-foam qualities could be further improved by purification procedures. Growth on G "15/17" foam plugs washed with pure EtOH were still somewhat inferior to growth on Gelrite 0.2% as regards dry weight but not shoot height.

Increasing agar or Gelrite concentrations led to a decrease of shoot height, dry weight (a similar ratio counts for fresh weight), root number and even length of root hairs.

Increase of agar from 0.50% to 1.0% in five steps led to a continuous decrease of pH after growth of appr. 0.4 whereas the pH values of the surface of Gelrite media (0.15–0.65%) remained nearly constant.

Compensating the different chemical composition of the utilized agar by addition of Al, Cu, Sr, Ti, V and Na and that of Gelrite by addition of potassium sulfate and Si left the superior properties of Gelrite media unchanged.

The brittleness or brittle point of Gelrite media was in the low concentration range nearly identical with agar media but in the range above 0.25% higher.

Gelrite media seemed to be more "elastic" as the dynamic gel strength was found to be linear for a larger concentration range than for agar media. In addition syneresis of Gelrite media seemed to be more distinctive and after growth the gels were obviously more liquid than agar gels. This indicates more lightly bound resp. associated water than in agar media.

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