In deep water rice plants, it is crucial for the leaves and upper parts of the shoot to remain above the water surface. Which of the following plant growth regulators promotes the rapid internode or petiole elongation required for this adaptation?

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Ethylene is a gaseous plant growth regulator that plays a significant role in various physiological processes. In deep water rice plants, ethylene promotes rapid internode and petiole elongation. This rapid growth ensures that the leaves and upper parts of the shoot remain above the water surface, which is essential for gas exchange and survival in flooded conditions. Answer: Ethylene