Explanation:

When GA3 (gibberellic acid) is applied to rice seedlings, the plant will show extra elongation. This response is due to the role of gibberellins in plant growth and development.

Gibberellic Acid (GA3)
- Gibberellic acid is a plant hormone that belongs to the class of gibberellins.
- It is involved in various physiological processes in plants, including stem elongation, seed germination, flowering, and fruit development.

Role of Gibberellins in Plant Growth
- Gibberellins promote cell elongation by stimulating the synthesis of enzymes that break down cell wall components.
- They also induce the division of cells in the stem, leading to elongation.
- In rice seedlings, the application of GA3 leads to increased internode length, resulting in extra elongation of the plant.

Effects of GA3 on Rice Seedlings
- When GA3 is applied to rice seedlings, it promotes stem elongation, causing the plant to grow taller.
- The internodes, which are the spaces between the nodes (points where leaves or branches are attached to the stem), become longer.
- This extra elongation results in the plant appearing taller and more stretched out compared to untreated seedlings.
- It is important to note that GA3 does not directly affect ripening or flowering in rice seedlings. Therefore, options a) delayed ripening and b) early flowering are incorrect.
- Similarly, GA3 does not cause dwarfing, so option c) dwarfing is also incorrect.

Conclusion
When GA3 is applied to rice seedlings, the plant shows extra elongation. This response is due to the role of gibberellins in promoting cell elongation and stimulating the synthesis of enzymes that break down cell wall components.