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 a 3:1 ratio, 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.
Iron was added in the form of the tartrate salt to prevent chlorosis, which can occur when free iron (such as ferrous sulfate in Knudson C) is used due to its low availability after precipitation.
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. The iron tartrate is also a slightly soluble compound, and an undissolved fraction remains even after autoclaving. 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.
At the time of development, the commercial availability of the iron complexes used today was severely limited. Therefore, in addition to this original formulation, we also offer modifications with other complex compounds such as Fe-EDTA.
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 |
| Release class: |
Release class 0 |
| Media components: |
macro elementsmicro elements |
| 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 |
| Iron(III) tartrate |
23,13 |
mg/l |
| Manganese sulfate monohydrate |
5,68 |
mg/l |
|
| GHS-Pictograms: |
00 |
| Dosage: |
1.626 g/l |
| References: |
Knudson, Lewis. "A new nutrient solution for the germination of orchid seed." Amer. Orchid Soc. Bull. 15 (1946): 214-217.
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. |
The newest safety datasheets or certificate of analysis (CoA) can get requested by using our contact form. They also can be requested during the order process or directly per mail via [email protected].
