SEQUENTIAL ELONGATION OF INTERNODES OF DEEP-WATER RICE AT DIFFERENT WATER DEPTHS

Deepwater rice (DWR) was grown for four seasons in Thailand where fields were deeply flooded 50-80 days after seedling emergence. After flooding commenced, water levels increased at rates of 2-6 cm/day until reaching maximum depths of 1-3 m. The DWR plants survived by elongation of internodes, thus increasing plant height and keeping the foliage above water. The total number of internodes with marked elongation (5-30 cm) ranged from 14, where water reached a maximum of 1 m to 20 at 3 m maximum water depth, but the five uppermost appeared to elongate under the influence of reproduction rather than water level. New nodes were produced at intervals of 10-12 days, and the most recently formed internodes elongated. The number of internodes formed at the base of the stems during the dryland phase which did not elongate depended on the time of commencement of flooding, but plants appeared able to elongate after production of the fourth node. Grain-yield was not decreased in the deepest water. © 1990.