Plant Tissue Culture Medium Short Notes | Biotechnology

In this article we will discuss about:- Composition of Culture Medium

• Media used in plant tissue culture contain nutritional components.
• Nutritional components are essential for growth and development of cultured tissue
• The success of the tissue culture depends very much on the type of culture media used.
• Each plant tissue culture medium must contain the following essential components to support invitro plant growth.
• These are as follows. 

1) Macro inorganic nutrients

2) Micro inorganic nutrients

3) Iron (as chelating agent)

4) Vitamins

5) Carbon sources

6) Organic nitrogen

7) Plant growth regulators

8) Agar (as gelling substance)

1. Macro nutrients

• Need of macro nutrients is higher.
• It is present in milli molar (mM) quantities (more than 30 ppm/1 or mg/1)
• Macro nutrients provide both anions and cations for the plant cells.
• Macro nutrients are nitrogen (as NO3 and NH4),phosphorus(PO4),potassium(K),sulphur(a s SO4),magnesium(Mg),and calcium(Ca).
• Macro nutrients have structural and functional role in protein synthesis, cell wall synthesis enzyme Co-factors and membrane integrity.

Nitrogen:

• In organic form used as amino acids, different organic acids and casein hydrolysate.
• In inorganic form used as Nitrate or ammonia.
• Nitrogen is major component of all plant tissue culture media.
• Nitrogen helps to synthesis complex organic molecule.

Potassium:

• K ion is present in high concentration in the cytoplasm (100-200 mM) and in chloroplast(20-200 mM).
• K+ is essential for mentaining the ion balancing, activation of many enzymes. Maintaining osmotic pressure and osmotic regulation of cells.

Calcium:

• Calcium functions with different enzymes as Co- factor and bound to the cell wall and cell membrane.
• It gives strength to cell wall.
• It helps in the regulation of the the cell membrane structure.
• Deficiency causes disintegration of the membrane and shoot tip necrosis.
• Important in cell and root multiplication.
• Supplied as calcium chloride and calcium nitrate.

Phosphorus:

• Very important for energy metabolism.
• Essential element for DNA & RNA.
• Deficiency may cause delayed growth and dark green coloure of leaves.
• Supplied as sodium hydrogen phosphate or potassium hydrogen phosphate.

Magnesium:

• Essential for enzymatic reactions, energy metabolism(ATP synthesis).
• Supplied as magnesium sulphate.

Sulphur:

• Important substance.
• Deficiency of Sulphur inhibits protein synthesis and decreases Chlorophyll in leaves.
• Supplied as magnesium Sulphate and Potassium Sulphate.

2) Micro Nutrients

• Boron(B), Manganese(Mn),Zinc(Zn),Molybdenum(Mo),Copper(Cu),Cobalt(Co).
• Used in less amount less than 30ppm.(mg/l).
• Concentration is always in uM.

Zinc:

• Zn plays an active role in protein synthesis and in the synthesis of tryptophan.
• Supplied as Zinc Sulphate.

Manganes:

• Plays an important role in the Hill reaction of photasynthesis.
• Required in many enzymatic activities.
• Supplied as Manganese Sulphate.

Copper:

• Copper plays important role in photosynthesis.
• Intermediate of the electron transport chain between photo system 1 & 2
• Deficiency leads to decrease in photosynthesis.
• Supplied as Copper Sulphate.

3. Iron

• Important Enzyme Co-factor Supplied in uM quantities.
• It is supplemented with chelators and Complex compounds due to its solubility problem.
• Supplied as Na2FeEDTA
• Iron deficiency have severe effects on the growth and development plant cells.

4. Vitamins

• Plant synthesis required vitamins.
• Essential for many biochemical reaction.
• Cultured cell are capable to produle vitamins at some level.
• They require an exogenous supply of different vitamins for optimum growth.
• Most usable vitamins are Thiamine, Pyridoxine nicotinic acid Vitamin B Complex.

5) Carbon sources

Hexitols

• Most tissue culture media have this compound.
• Essential for seed germination, sugar transport, carbohydrate metabolism, membrane structure and cell wall formation.
• Mannitol and sorbital are hexitols.

Carbohydrate

• Cells and tissue reduires exogeneous supply of carbohydrates to replace the carbon which the plant normally fixes from the atmosphere by photosyntheis.
• Supplied by adding sucrose.
• Concentration is 20-30 gm/l.

6) Organic nitrogen

Amino Acids:

• Glycine is the most common Amino Acid used in different culture media.
• It is not essential but Nitrogen containing Amino Acid enhance growth and plant regeneration.

Gelling Agent:

• Agar – Agar
• Agar is a natural product of seaweeds.
• Since 1658 agar-agar is obtain from red algae (Gelidium Gracilaria)
• With water it melts at 100’C and solidify at 45’C

Agarose:

• It is highly purified agar prepared from Gelidium sp. Of seaweed.
• Agarose melt and gel at temperatures below 30’C and dissolve through boiling.
• Agarose is much more expensive agar-agar

Gelrite or Phytagel:

• Gelrite is a naturally derived polymer and produced by the microbial termentation of a bacterium Pseudomonas elodea.
• It is low cost gelling agent.
• 0.1-0.2 % concentration pen litre required.

7. Plant growth regulators

• A plant hormone can be defined as a small organic molecule that elicits a physiological response at very low conc.
• PGS plays an important role in the phenotype.
• Act as messenger between environment and the genome.

Auxins:

• Essential for cell division, cell elongation, cell differentiation, organogenesis and embryogenesis, callus formation
• Natural form auxins are IAA, IBA, PAA
• Synthetic form of auxins are NAA, 2, 4-D.

Cytokinins:

• Cytokinins promote cell division, shoot proliferation and influence the cell cycle.
• Embryogenesis and inhibit roof formation.
• Synthetic form is 2-ip which is most active cytokinins.
• Natural forms are BAP and kinetin.

Gibberellins:

• It promotes stem elongation, bulb corm formation and embryo maturation but can inhibit callus growth and root induction.
• GA3 is most common gibberellins.

Abscisic acid:

• It inhibits shoot growth and germination of embryo.
• It is thermostable but light sensitive

Ph of tissue culturemedia

• Ph is adjusted between 5 & 5.8 before gelling and sterilization with the help of dilute NaOH, KOH or HCL.
• Ph below 5 will not gel properly.
• Ph above 6 may be too hard.