To increase the length of grape stalks gibberellin are applied. The mechanism of action of gibberellin exploited in this case is its

Options

A. ability to increase length of apex.
B. ability to increase in the length of the axis.
C. ability to avoid apical dominance.
D. all of these.

Answer

To solve the question regarding the mechanism of action of gibberellins in increasing the length of grape stalks, we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding Gibberellins**: Gibberellins are a class of plant hormones that play a crucial role in various growth processes in plants, including stem elongation, seed germination, and flowering.

2. **Application in Grapes**: In the context of grape cultivation, gibberellins are applied to increase the length of the grape stalks. This is particularly important for improving the quality and marketability of the grapes.

3. **Mechanism of Action**: The primary mechanism by which gibberellins increase the length of grape stalks is through their ability to promote elongation of the internodes (the segments of the stem between the nodes). This elongation results in longer grape stalks.

4. **Other Functions of Gibberellins**: Besides promoting internodal elongation, gibberellins also facilitate seed germination, stimulate the malting process in brewing, and can influence flowering. However, they do not directly affect apical dominance, which is more influenced by other hormones like cytokinins.

5. **Conclusion**: Therefore, the correct answer to the question is that gibberellins increase the length of the axis (internodal elongation), which is the mechanism exploited in the application to grape stalks.

### Final Answer:
The mechanism of action of gibberellins exploited in this case is its ability to increase the length of the axis (internodal elongation).

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