Murashige and Skoog (MS) Medium: The Gold Standard for Plant Tissue Culture
Introduction
Murashige and Skoog (MS) Medium, developed by plant physiologists Toshio Murashige and Folke K. Skoog in 1962, has become an essential cornerstone in the field of plant tissue culture. Widely regarded as the “gold standard,” MS medium supports in vitro plant growth by providing a well-suited nutrient environment for plant cells, tissues, and organs. Given its ability to promote regeneration, tissue multiplication, and callus formation, MS medium is widely utilized in research, agriculture, and biotechnology.
In this blog post, we will explore what MS medium is, its key ingredients, and common applications in plant tissue culture. We’ll also provide the basic formulation for preparing Murashige and Skoog (MS) medium on a per liter basis.
What is MS Medium?
Murashige and Skoog (MS) medium is a chemically defined plant tissue culture medium. Its development was a groundbreaking advance for plant science because it allowed researchers to grow plant tissues in vitro under controlled conditions. The medium contains a variety of essential nutrients, including macronutrients, micronutrients, vitamins, and a carbon source (typically sucrose), that are necessary for plant cell division, growth, and differentiation when cultivated in controlled environments.
MS medium is highly versatile because it can be adapted by adjusting factors such as the concentration of hormones (auxins and cytokinins), which determines the type of tissue culture outcome desired: callus formation, root development, shoot initiation, or even germination.
Key Components of MS Medium
MS medium includes the following components:
Macronutrients:
These are essential in large quantities for cell growth.- Nitrogen (N) as nitrate (NO₃⁻) and ammonium (NH₄⁺) sources
- Phosphate (PO₄³⁻)
- Potassium (K⁺)
- Calcium (Ca²⁺)
- Magnesium (Mg²⁺)
- Sulfate (SO₄²⁻)
Micronutrients:
These elements are required in trace amounts for enzymatic activities and metabolic processes.- Iron (Fe)
- Manganese (Mn)
- Zinc (Zn)
- Boron (B)
- Copper (Cu)
- Molybdenum (Mo)
- Cobalt (Co) – usually in negligible or trace amounts
Vitamins:
Vitamins aid in the enzymatic processes that regulate metabolic function.- Thiamine (Vitamin B1)
- Nicotinic acid (Niacin)
- Pyridoxine (Vitamin B6)
Carbon Source:
- Commonly, sucrose is used as a carbon and energy source, as plants grown in vitro do not photosynthesize well due to controlled lighting and closed conditions.
- Hormones (Plant Growth Regulators):
- Depending on the specific experiment and desired outcome, plant hormones can be added to the medium to control cell differentiation. Auxins (e.g., Indole-3-acetic acid [IAA], 2,4-Dichlorophenoxyacetic acid [2,4-D]) stimulate root initiation, whereas cytokinins (e.g., Kinetin, Benzylaminopurine [BAP]) promote shoot and meristem development.
Applications of MS Medium
Murashige and Skoog medium is widely employed in numerous plant biotechnology techniques and applications. Some of its main uses include:
Micropropagation:
MS medium can be tailored to regenerate plants from small tissue samples (explant). This is highly useful for propagating plants that are difficult to grow from seed or for the mass production of plant varieties with desirable traits.Callus Induction:
By adjusting nutrient concentrations and adding specific hormones, MS medium can induce callus formation (a mass of undifferentiated plant cells) from plant tissues.Genetic Engineering and Transformation:
MS medium is used as a selectable growth medium in experiments involving molecular transgenesis (e.g., Agrobacterium-mediated transformation) where desirable genetic traits can be introduced to the plant genome.Plant Regeneration:
Plant tissue (such as stem, leaf, or root explants) can be cultured in MS medium to regenerate entire plants. Different growth regulators (hormones) within MS medium determine whether roots, shoots, or entire plants will form.Embryo Rescue:
In cases where hybrid plants may produce viable embryos but not viable seeds, MS medium can be employed to help grow embryos and rescue them.- Somatic Embryogenesis:
MS medium also supports somatic embryogenesis, where plant embryos are generated from somatic or non-reproductive plant cells. This technique is fundamental to many plant breeding and genetic engineering projects.
MS Medium Formulation (Per Liter)
Here is the standard formulation for Murashige and Skoog (MS) medium, on a per liter basis:
| Component | Concentration |
|---|---|
| Macronutrients | |
| NH₄NO₃ (Ammonium Nitrate) | 1650 mg/L |
| KNO₃ (Potassium Nitrate) | 1900 mg/L |
| CaCl₂•2H₂O (Calcium Chloride) | 440 mg/L |
| MgSO₄•7H₂O (Magnesium Sulfate) | 370 mg/L |
| KH₂PO₄ (Potassium Phosphate) | 170 mg/L |
| Micronutrients | |
| H₃BO₃ (Boric Acid) | 6.2 mg/L |
| MnSO₄•H₂O (Manganese Sulfate) | 22.3 mg/L |
| ZnSO₄•7H₂O (Zinc Sulfate) | 8.6 mg/L |
| Na₂MoO₄•2H₂O (Sodium Molybdate) | 0.25 mg/L |
| CuSO₄•5H₂O (Copper Sulfate) | 0.025 mg/L |
| CoCl₂•6H₂O (Cobalt Chloride) | 0.025 mg/L |
| KI (Potassium Iodide) | 0.83 mg/L |
| Iron Source | |
| Na₂-EDTA (Disodium EDTA) | 37.3 mg/L |
| FeSO₄•7H₂O (Ferrous Sulfate) | 27.8 mg/L |
| Vitamins | |
| Thiamine-HCl (Vitamin B1) | 0.1 mg/L |
| Pyridoxine (Vitamin B6) | 0.5 mg/L |
| Nicotinic Acid (Niacin) | 0.5 mg/L |
| Carbon Source | |
| Sucrose | 30,000 mg/L |
| Agar (if solid medium) | 7–8 g/L |
Note: pH of the medium is typically adjusted to between 5.6 and 5.8 before autoclaving. If solid medium is required, agar is added before sterilization to solidify the medium post-autoclaving.
Conclusion
Murashige and Skoog (MS) medium remains one of the most widely used plant culture media in laboratories around the world. Its broad range of applications, from basic research to agricultural innovation, has made it indispensable for scientists. By providing the right combination of macronutrients, micronutrients, vitamins, and hormones, MS medium allows for the successful in vitro growth and multiplication of plant cells, helping push the boundaries of plant research. Whether you’re looking to clone plants on a massive scale or explore genetic modifications, MS medium is a versatile and reliable foundation upon which your plant tissue culture experiments can flourish.