Question: 125 Which hormone promotes internode/petiole elongation in deep water rice?
(1) Ethylene
(2) 2,4-\mathrm{D}
(3) \mathrm{GA}_{3}
(4) Kinetin
Answer: Option (1)
Explanation:
Deep water rice grows in flooded conditions where the plant must elongate its internodes or
petioles to keep leaves above the water surface.
Under submerged conditions, ethylene accumulates in plant tissues due to
reduced diffusion into the surrounding water.
This accumulated ethylene stimulates rapid internode and petiole elongation,
allowing the plant to survive flooding.
Gibberellins promote stem elongation in many plants, but in deep water rice,
the specific hormone responsible for elongation under flooded conditions is ethylene.
Therefore, ethylene promotes internode and petiole elongation in deep water rice.
Hence, Option (1) is the correct answer.