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Research indicates that endogenous hormone concentrations, rather than exogenous application levels, ultimately determine organogenic differentiation. Among the various [[Cytokinin|cytokinins]] (2iP, BAP, thidiazuron, kinetin, and zeatin) used for shoot induction, BAP has demonstrated superior efficacy and widespread application. [[Auxin|Auxins]] similarly influence organogenic pathways, with 2,4-D commonly used for callus induction in cereals, though organogenesis typically requires transfer to media containing [[Indole-3-acetic acid|IAA]] or [[1-Naphthaleneacetic acid|NAA]] or lacking 2,4-D entirely. The auxin-to-cytokinin ratio largely determines which organs develop.{{cn|date=June 2025}}
[[Gibberellic acid]] (GA3) contributes to cell elongation and meristemoid formation, while unconventional compounds like tri-iodobenzoic acid (TIBA), [[abscisic acid]] (ABA), kanamycin, and auxin inhibitors have proven effective for recalcitrant species. Natural additives like ginseng powder can enhance regeneration frequency in certain cultures. Since ethylene typically suppresses shoot differentiation, inhibitors of ethylene synthesis such as aminoethoxyvinylglycine (AVG) and silver nitrate (AgNO3) are often employed to promote organogenesis, with documented success in wheat, tobacco, and sunflower cultures.{{cn|date=June 2025}}
Agar is not an essential component of the culture medium, but quality and quantity of agar is an important factor that may determine a role in organogenesis. Commercially available agar may contain impurities. With a high concentration of agar, the nutrient medium becomes hard and does not allow the diffusion of nutrients to the growing tissue. It influences the organogenesis process by producing adventitious roots, unwanted callus at the base, or senescence of the foliage. The pH is another important factor that may affect organogenesis route. The pH of the culture medium is adjusted to between 5.6 and 5.8 before sterilization. Medium pH facilitates or inhibits nutrient availability in the medium; for example, ammonium uptake in vitro occurs at a stable pH of 5.5 (Thorpe et al., 2008).
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