In addition to auxins________must be supplied to culture medium to obtain a good callus in plant tissue culture,

Options

A. ABA
B. cytokinins
C. gibberellins
D. ethylene

Explanation

To answer the question, "In addition to auxins, ________ must be supplied to culture medium to obtain a good callus in plant tissue culture," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Role of Auxins**: Auxins are plant hormones that promote cell elongation and are crucial for the initial stages of plant tissue culture, particularly in the formation of callus.

2. **Define Callus**: Callus is an unorganized and undifferentiated mass of cells that arises from plant tissues. It consists of dividing cells that can eventually differentiate into various plant structures.

3. **Identify the Need for Other Hormones**: While auxins are essential for initiating callus formation, other hormones are also necessary to promote the growth and differentiation of the callus.

4. **Recognize the Role of Cytokinins**: Cytokinins are another class of plant hormones that promote cell division and are particularly important for shoot regeneration from the callus.

5. **Balance Between Auxins and Cytokinins**: The balance between auxins and cytokinins is critical for the successful development of callus and subsequent regeneration of shoots and roots. Auxins primarily promote root formation, while cytokinins promote shoot formation.

6. **Conclude the Answer**: Therefore, in addition to auxins, cytokinins must be supplied to the culture medium to obtain a good callus in plant tissue culture.

### Final Answer:
In addition to auxins, **cytokinins** must be supplied to the culture medium to obtain a good callus in plant tissue culture.

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