The Vacin & Went or VW medium is an optimization following studies of the pH stability of Knudson C solution, which can be used for asymbiotic germination of orchid seeds. The formula was developed to stabilize the pH, which can fall to suboptimal levels after autoclaving and after prolonged periods of culture in weakly buffered media (Vacin & Went, 1949).
Similar to the Knudson C (Knudson, 1946), it is rather minimalistic in design, containing only iron and manganese in addition to the essential macroelements. Other trace elements were supplemented only by impurities of the individual components, especially by using a high agar concentration.
This modification contains iron EDTA instead of iron tartrate. At the time of the development of the original VW medium, stable chelate complexes were not yet widely distributed. Over time, they became more common due to better nutrient availability. For example, Lim-Ho (1981) used the VW medium with Fe-EDTA for various culture phases in the in vitro propagation of Arachnis.
Notes:
The VW medium is not completely soluble in water. Vacin & Went indicated a solubility of 0.2 g/l at 25 °C for the calcium phosphate. However, the correct value is 0.02 g/l. The undissolved portion remains as a suspension and acts as an acidity regulator and gradually releases further calcium, respectively. To ensure uniform distribution, the medium should therefore be inverted several times shortly before pouring into the culture vessels (shaking may lead to undesirable foaming).
Due to the insoluble components, the medium is not suitable for sterile filtration.
In many cases, it can be helpful to enrich the VW medium with vitamins or complex additives such as coconut water to improve germination rate.
| Item information |
Value |
| GHS-Pictograms: |
00 |
| Specifications: |
Formula
| Component |
Amount |
Unit |
| Calcium phosphate |
200 |
mg/l |
| Potassium nitrate |
525 |
mg/l |
| Potassium dihydrogen phosphate |
250 |
mg/l |
| Magnesium sulfate (anh.) |
122 |
mg/l |
| Ammonium sulfate |
500 |
mg/l |
| Fe-EDTA trihydrate |
42.11 |
mg/l |
| Manganese sulfate monohydrate |
5.68 |
mg/l |
|
| Dosage: |
1.645 g/l |
| References: |
Knudson, Lewis. "A new nutrient solution for the germination of orchid seed." Amer. Orchid Soc. Bull. 15 (1946): 214-217.
Lim‐Ho, C.L. "Experimental findings of the tissue culture of orchid hybrids at the Singapore Botanic Gardens." Gard. Bull. 34 (1981): 148–160.
Vacin, Emil F., and F. W. Went. "Some pH changes in nutrient solutions." Botanical Gazette 110.4 (1949): 605-613.
|
| Storage Temperature: |
15 - 25 °C |
| OE-Warning: |
The absence of a classification according to GHS/CLP or warnings does not indicate that the product is not dangerous. |
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