Preece Enabling Medium

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Understanding Preece Enabling Medium: A Tissue Culture Essential

Tissue culture is an invaluable technique widely used in plant biotechnology, molecular biology, and genetics for propagating plants under sterile conditions. It enables the controlled growth of plant cells, tissues, or whole plants in an artificial nutrient medium under aseptic conditions. Among the various available tissue culture media, Preece Enabling Medium (PEM) is one formulation that plays a crucial role in enabling successful propagation and growth of plant tissues.

In this blog post, we’ll take an in-depth look at Preece Enabling Medium, its formulation, and its applications in tissue culture.


What is Preece Enabling Medium?

Preece Enabling Medium (PEM) is a specialized tissue culture medium designed for the growth, proliferation, and maintenance of plant cells and tissues in vitro. Named after Dr. Alan Preece, a prominent researcher in plant tissue culture, PEM is widely used in laboratories for the initiation of cultures from meristem or explants, and for the multiplication and rooting of plantlets.

The medium supplies plant tissues with the necessary nutrients, vitamins, organic compounds, and hormones required for healthy growth and development in vitro. PEM often serves as the foundational medium for more specialized plant culture systems where modifications can be made to tailor the conditions to a specific plant species or cultivar.


Applications of Preece Enabling Medium

Preece Enabling Medium is typically used for:

  1. Meristem Culture: PEM is a preferred choice for initiating cultures from plant meristems, which include the actively dividing tip of the plant shoot or root.

  2. Micropropagation: It is heavily used in micropropagation (clonal propagation) due to its ability to support the rapid multiplication of plant tissues and explants.

  3. Callus Induction: PEM can be modified slightly to promote callus induction – the process where undifferentiated plant cells grow from explants.

  4. Somatic Embryogenesis: The medium can support the development of somatic embryos from differentiated plant cells; this is particularly useful in genetic engineering and plant breeding programs.

  5. Rooting of Shoots: In many tissue culture protocols, PEM is used for inducing and promoting the rooting of regenerated shoots.


Formulation of Preece Enabling Medium (Per Liter)

The formulation of Preece Enabling Medium involves macronutrients, micronutrients, vitamins, carbohydrates, and growth regulators. Here’s its standard composition per liter, which can be adjusted depending on the plant’s specific needs.

Macronutrients:

  1. NH₄NO₃ (Ammonium nitrate) – 1650 mg
  2. KNO₃ (Potassium nitrate) – 1900 mg
  3. CaCl₂·2H₂O (Calcium chloride dihydrate) – 440 mg
  4. MgSO₄·7H₂O (Magnesium sulfate heptahydrate) – 370 mg
  5. KH₂PO₄ (Potassium dihydrogen phosphate) – 170 mg

Micronutrients:

  1. MnSO₄·H₂O (Manganese sulfate monohydrate) – 22.3 mg
  2. ZnSO₄·7H₂O (Zinc sulfate heptahydrate) – 8.6 mg
  3. CuSO₄·5H₂O (Copper sulfate pentahydrate) – 0.025 mg
  4. Na₂MoO₄·2H₂O (Sodium molybdate dihydrate) – 0.25 mg
  5. H₃BO₃ (Boric acid) – 6.2 mg
  6. CoCl₂·6H₂O (Cobalt chloride hexahydrate) – 0.025 mg
  7. KI (Potassium iodide) – 0.83 mg

Chelated Iron Source:

  1. FeSO₄·7H₂O (Ferrous sulfate heptahydrate) – 27.8 mg
  2. Na₂EDTA (Disodium Ethylenediaminetetraacetic acid) – 37.3 mg

Vitamins:

  1. Thiamine (Vitamin B₁) – 0.1 mg
  2. Pyridoxine HCl (Vitamin B₆) – 0.5 mg
  3. Nicotinic Acid – 0.5 mg

Carbon Source (Carbohydrate):

  1. Sucrose (Table sugar) – 30 grams

Plant Growth Regulators*:

  1. NAA (Naphthaleneacetic acid) – 0.5 mg
  2. BAP (6-Benzylaminopurine) – 1.0 mg

(*The concentration of growth regulators may vary according to the type of culture and the species of the plant.)

Gelling Agent:

  1. Agar – 7 grams if a solid medium is required.


Preparation of Preece Enabling Medium:

  1. Weigh and dissolve the macronutrients in about 800 mL of distilled water. Ensure each component is completely dissolved before adding the next.

  2. Add micronutrients and the chelated iron mixture (EDTA/FeSO₄) to the solution.

  3. Dissolve the vitamins, ensuring they mix properly with the basal medium.

  4. Add the sucrose and any growth regulators (BAP, NAA, etc.) as per your protocol.

  5. If preparing a solid medium, add agar and heat to dissolve properly.

  6. Adjust the pH of the medium to 5.8 using 1M KOH or HCl, as needed.

  7. Finally, top up the solution to 1 liter with distilled water, and autoclave at 121°C for 20 minutes to sterilize.


Final Thoughts

Preece Enabling Medium is an efficacious and flexible growth medium for various stages of plant tissue culture. Whether you’re working with meristem tips, micropropagating plantlets, or preparing callus cultures for somatic embryogenesis, PEM proves to be an optimal basal medium.

By modifying its ingredients, particularly the growth regulators, scientists can create a tailored environment for many plant species, ensuring maximal growth potential and healthier in vitro cultures. If you’re venturing into the world of plant tissue culture for the first time or are looking to diversify your in-lab media, Preece Enabling Medium provides an excellent foundation to build upon.


Overall Recommendations:

  • Always check for species-specific nutrient needs before settling on hormone concentrations or micronutrient levels.
  • Keep your workspace sterile to avoid contamination, which is a critical concern in tissue culture practices.
  • Trial and error with plant growth regulators might be necessary to find the best conditions for your specific plant species.

By adapting the PEM formulation according to plant-specific factors, researchers can achieve excellent results in plant propagation and experimental studies.


Happy culturing!

Disclaimer: The formulation given here is a generalized outline based on widely available data on Preece Enabling Medium. Consult specific plant tissue culture manuals or protocols before attempting any tissue propagation involving rare or uncommon species.

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