Plant tissue culture media provides all the necessary nutrients and growth regulators required for in vitro growth and development of plant cells, tissues, and organs. It is a carefully formulated blend designed to support aseptic cultivation.
Here's a breakdown of the key components:
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Macronutrients: These are essential elements needed in relatively large quantities. Examples include:
- Nitrogen (N): Crucial for protein and nucleic acid synthesis.
- Phosphorus (P): Important for energy transfer and membrane structure.
- Potassium (K): Involved in enzyme activation and osmotic regulation.
- Calcium (Ca): Essential for cell wall structure and signaling.
- Magnesium (Mg): A component of chlorophyll and an enzyme activator.
- Sulfur (S): A constituent of certain amino acids and proteins.
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Micronutrients: These elements are required in smaller amounts but are still vital for plant metabolism. Examples include:
- Iron (Fe): Important for chlorophyll synthesis and electron transport.
- Manganese (Mn): Involved in photosynthesis and enzyme activation.
- Zinc (Zn): An enzyme activator and important for growth regulation.
- Boron (B): Essential for cell wall synthesis and carbohydrate metabolism.
- Copper (Cu): A component of certain enzymes.
- Molybdenum (Mo): Important for nitrogen metabolism.
- Chlorine (Cl): Involved in photosynthesis and osmotic regulation.
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Vitamins: These organic compounds act as cofactors for various enzymes. Common vitamins added to plant tissue culture media include:
- Thiamine (Vitamin B1): Involved in carbohydrate metabolism.
- Nicotinic acid (Niacin): A component of NAD and NADP.
- Pyridoxine (Vitamin B6): Involved in amino acid metabolism.
- Myo-inositol: Involved in cell wall synthesis and signal transduction.
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Amino Acids and Nitrogen Supplements: These provide a readily available source of nitrogen for plant cells.
- Amino acids like glycine, alanine, and arginine are often added.
- Other nitrogen sources like casein hydrolysate can also be used.
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Sugars: Serve as a carbon source and provide energy for plant cells. Sucrose is the most commonly used sugar, but other sugars like glucose and fructose can also be used.
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Undefined Organic Supplements: Complex mixtures of organic compounds that can enhance plant growth. Examples include:
- Coconut water: Contains various growth factors and nutrients.
- Yeast extract: A source of vitamins, amino acids, and other organic compounds.
- Casein hydrolysate: A source of amino acids and peptides.
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Solidifying Agents or Support Systems: Used to provide a solid or semi-solid support for plant tissues.
- Agar: The most common solidifying agent.
- Gellan gum (Gelrite): Another gelling agent used in plant tissue culture.
- Liquid media can be used with support systems like filter paper bridges or polyurethane foam.
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Plant Growth Regulators (PGRs): Hormones that regulate plant growth and development. The most commonly used PGRs in plant tissue culture are:
- Auxins: Promote cell division, cell elongation, and root formation. Examples include: Indole-3-acetic acid (IAA), 2,4-Dichlorophenoxyacetic acid (2,4-D), and Naphthaleneacetic acid (NAA).
- Cytokinins: Promote cell division, shoot formation, and delay senescence. Examples include: Kinetin (KIN), 6-Benzylaminopurine (BAP), and Zeatin.
- Gibberellins (GAs): Promote stem elongation and seed germination.
- Abscisic acid (ABA): Involved in stress responses and dormancy.
- Ethylene: Involved in fruit ripening and senescence.
Different plant species and tissue types may require different formulations of culture media for optimal growth and development. Common media formulations include Murashige and Skoog (MS) medium, Gamborg's B5 medium, and Woody Plant Medium (WPM). The precise composition of the media is crucial for achieving the desired results in plant tissue culture.
