Describe the various components of plant tissue culture media.
The success of in vitro culture of plants mainly depends upon the selection of the right composition of culture medium. Culture media used for in vitro plant cultures broadly contain the following components:
Inorganic components form an essential part of the nutrient media. These include macronutrients like MgSO₄·7H₂O, KH₂PO₄, KNO₃, NH₄NO₃, and CaCl₂·2H₂O, and micronutrients like H₃BO₃, MnSO₄·4H₂O, ZnSO₄·7H₂O, CuSO₄·5H₂O, and KI. These are required for optimal growth and development of the explant.
Organic supplements include vitamins such as Thiamine HCl, Pyridoxine HCl, and Nicotinic acid. Other organic supplements include Myoinositol and Glycine. These support the metabolic activities of the cultured tissues.
Carbon source is provided mainly in the form of sucrose (20-30 mg l⁻¹). Since the explants grow under heterotrophic conditions in culture, an external carbon source is essential for energy and metabolism.
Plant growth hormones are added to the media to regulate growth and differentiation. The composition varies depending on the plant species, whether monocot or dicot, domesticated or wild. Gelling agents are used to solidify the media. The pH of the nutrient media is usually adjusted to about 5.8 to 6.0, as it affects nutrient uptake and solubility of media salts.
Antibiotics can be used to suppress bacteria, and antifungal agents are used for mould infections in cultures. MS (Murashige and Skoog) media is the most commonly used media composition in plant tissue culture.
Explanation
This answer covers all six components of plant tissue culture media as listed in the textbook context. The student has organized the answer into clear paragraphs covering inorganic components (with examples from the table), organic supplements, carbon source, plant growth hormones, gelling agents, and antibiotics. The answer also mentions the importance of pH adjustment (5.8-6.0) and identifies MS media as the most commonly used composition. The word count is appropriate for a 5-mark question, and key terms are bolded as required.