In tissue, culture, shoot and root regenerations are generally controlled by

Options

A. Changing the amount of gibberellin
B. Auxin-cytokinin balance
C. Ethylene-ABA balance
D. The process of subculturing

Answer

**Step-by-Step Solution:**

1. **Understanding Tissue Culture**: Tissue culture is a technique used to grow plants in a controlled environment, allowing for the regeneration of shoots and roots from plant tissues.

2. **Role of Hormones**: In tissue culture, the regeneration of shoots and roots is primarily influenced by plant hormones. These hormones regulate various physiological processes, including cell division and differentiation.

3. **Identifying Key Hormones**:
- **Gibberellins**: These hormones are known as senescence hormones that promote growth and development but are not directly responsible for shoot and root regeneration.
- **Auxins**: These hormones promote cell elongation and are crucial for the growth of roots and shoots. They are involved in the regulation of various developmental processes.
- **Cytokinins**: These hormones promote cell division and are essential for the growth of shoots. They work in conjunction with auxins to regulate the growth and differentiation of plant tissues.

4. **Balancing Auxins and Cytokinins**: The balance between auxins and cytokinins is critical for successful shoot and root regeneration. Auxins are typically more concentrated in root formation, while cytokinins promote shoot formation.

5. **Other Hormones**:
- **Ethylene**: This hormone is primarily involved in the ripening of fruits and does not play a significant role in tissue culture regeneration.
- **Abscisic Acid**: This hormone is involved in stress responses and also does not contribute to shoot and root regeneration in tissue culture.

6. **Conclusion**: The correct answer to the question is that shoot and root regenerations in tissue culture are generally controlled by the balance of auxins and cytokinins.

**Final Answer**: Auxin and cytokinin balance.

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