Root water extraction and shoot water potential in upland rice and corn
1999
Murty, M.V.R. | Kondo, M. | Aragones, D.V. (International Rice Research Inst., MCPO Box 3127, Makati City 1271 (Philippines))
Upland rice culture is characterized by water shortage cycles during the growth periods. Water uptake ability by roots is a critical component for sustainable productivity of upland rice. Root growth and water extraction in upland rice and corn were characterized in a field experiment with different nitrogen levels in the IRRI farm in the 1998 dry season. Genotypic variations in plant water potentials and potential gradients were characterized through a solution culture experiment. About 80 to 85 percent of root lengths were in shallow depths irrespective of nitrogen applications in rice. Root lengths were marginally higher in deeper layers in corn. The root growth was more in favor of deeper layers during drought in corn. However, this was not so in rice. Fraction of total root length and mass distribution in deeper layers increased under stress in corn. Water uptake in the upper layer helped corn to maintain a larger water extraction during the stress period. Nitrogen helped rice roots to extract minimal water from deeper layers. A wider variation in leaf water potentials was observed among cultivars. Japonica varieties in general maintained a higher leaf water potential. Potential gradients between leaf and stem were larger in rice compared with corn. In general, potential gradients in indica cultivars were larger than in japonica varieties. Indica shoot resistance seems to be larger in rice than in corn. Indica cultivars seem to exhibit higher shoot resistance as compared to japonica varieties
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