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and zinc (Zn). Amino acids and vitamins are common organic supplements that are used in culture media. Amino acids serve as nitrogen source and commonly used amino acids are arginine, asparagine, glycine or proline. Vitamins added in the culture medium are thiamine (Vitamin B1), nicotinic acid (Vitamin B3) and pyridoxin. For in vitro cultures, sucrose is considered as the best carbon source and is used at concentration of about 2–5 percent. Other sources for carbon are glucose, fructose and mannose. Plant growth hormones play a vital role in plant’s growth and development, and are critical components of media. These are required in minute quantities in the nutrient media. There are five main categories of growth hormones i.e., Auxin, Cytokinin, Gibberellin, Abscisic acid and Ethylene. However, auxins and cytokinin are most commonly used in plant tissue culture. Ratio of their concentrations determines the type of organs produced from the cultured cell or tissues. For example, higher concentration of cytokinin results in shoot regeneration in general. Further, different plant tissues need different amount of hormones for their growth and therefore, depending upon the type of explant, their concentration may vary in the nutrient media. Gelling agent is required for solid culture media. Agar is the most commonly used gelling agent and is ideal for routine applications. Further, pH of the nutrient media is usually adjusted to about 5.8 to 6.0. Increase in the pH increases the hardness of the medium and decrease in pH leads to poor solidification of the media. pH of the nutrient media also affects the uptake of the nutrients by plant cells and solubility of the media salts. Antibiotics can be used to suppress the bacteria and antifungal agents for mould infections in cultures. The recipe of plant tissue culture media is usually directed by plant species, however (MS) / media is the most commonly used media composition in plant tissue culture. 7.4 C ulture T ypes Plant Tissue Culture may be categorised as organ culture, callus culture, cell suspension culture, protoplast 174 BiotechnologyXII Reprint 2025-26