Which hormone promotes internode / petiole elongation in deep water rice?

Ethylene (${\mathrm{C}}_2{\mathrm{H}}_4$) is a gaseous hormone which is mainly involved in the fruit ripening process. The major physiological effects of ethylene are:

• Ethylene promotes rapid internode/petiole elongation in deep water rice plants.
• Ethylene also promotes root growth and root hair formation, thus helping the plants to increase their absorption surface.
• Ethylene breaks seed and bud dormancy, initiates germination in peanut seeds, sprouting of potato tubers.