Can you provide more details on the specific concentrations of auxins and cytokinins used in micropropagation?

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In micropropagation, the specific concentrations of auxins and cytokinins are crucial for optimizing plant tissue culture processes. These concentrations can vary significantly depending on the plant species and the desired outcome (e.g., shoot proliferation, root induction, or somatic embryogenesis). Here are some detailed examples and guidelines based on recent studies:

Auxins

1. Indole-3-Butyric Acid (IBA)
   • Concentration: 1.0 µM
   • Application: Effective for root induction in 'Shine Muscat' grapevines. This concentration led to the highest percentage of root formation and was more effective than IAA (Indole-3-acetic acid) and NAA (Naphthalene acetic acid).
2. Naphthalene Acetic Acid (NAA)
   • Concentration: 4.0 µM
   • Application: Used for root initiation in some species but associated with issues such as toxicity and callus formation, which can hinder successful acclimatization of plantlets.
3. Indole-3-Acetic Acid (IAA)
   • Concentration: Varies, but generally less effective than IBA for root induction due to its tendency to decompose under medium and light conditions, reducing its interaction with cytokinins.

Cytokinins

1. Benzyladenine (BA)
   • Concentration: 2.0 µM
   • Application: Optimal for shoot induction in 'Shine Muscat' grapevines, leading to the highest shoot number and effective in combination with IBA for root induction.
2. Kinetin (KIN)
   • Concentration: 16.0 µM
   • Application: Resulted in the lowest shoot number among the cytokinins tested, indicating that it may not be as effective for shoot proliferation in some species.
3. Thidiazuron (TDZ)
   • Concentration: Varies, but generally used at lower concentrations compared to BA and KIN due to its potent cytokinin activity, which can sometimes lead to excessive callus formation.

Combined Use of Auxins and Cytokinins

1. IBA and BA Combination
   • Concentrations: 1.0 µM IBA + 2.0 µM BA
   • Application: Effective for both shoot multiplication and root induction in 'Shine Muscat' grapevines, with a high survival rate of plantlets during acclimatization.
2. NAA and BAP Combination
   • Concentrations: 0.5 mg/L NAA + 4.0 mg/L BAP (Benzyladenine Phosphate)
   • Application: Resulted in the highest number and length of shoots, demonstrating the synergistic effect of auxins and cytokinins in micropropagation.

General Guidelines

• Auxin Concentrations: Typically range from 0.1 mg/L to 10 mg/L, depending on the specific auxin and the plant species being cultured.
• Cytokinin Concentrations: Generally used at concentrations between 0.1 mg/L and 10 mg/L, with specific concentrations optimized for each plant species and desired outcome.
• Ratio of Cytokinin to Auxin: A common ratio used for shoot proliferation is 10:1 (cytokinin:auxin), which promotes shoot growth while inhibiting root formation.

These concentrations and combinations are based on empirical data and should be adjusted based on the specific requirements of the plant species being cultured and the desired outcomes of the tissue culture process.