Varietal Differences in the Growth and Dry-Matter Production during Vegetative Growth in Rice under Upland Cultivation Conditions with Water Stress : A comparison of Japonica, Indica and Japonica-Indica hybrid cultivars(Crop Physiology and Cell Biology)

Since rice is highly susceptible crops to water stress, it is important to improve drought resistance to increase and stabilize the rice yield under upland cultivation conditions. This study was conducted to elucidate the morphological and physiological characteristics related to drought resistance in diverse rice germplasm. Six cultivars including Japonica, Indica and Japonica-Indica hybrid cultivars were grown in a pot, suffering the same soil water deficit conditions at a vegetative growth stage. The reduction in leaf area growth and in dry matter production under water stress was smaller in IR36 and two Japonica -Indica hybrid cultivars, Suweon 287 and Suweon 290 than Japonica and Indica upland cultivars, Toyohatamochi and IRAT109. The reduction in leaf photosynthetic rate was also smaller in Suweon 287 and Suweon 290. IR36, Suweon 287 and Suweon 290 showed a semi dwarf morphological characteristic with a large tiller number. The partitioning of the net production directed much to roots and less to leaves under the water stress conditions in all cultivars tested. IR36 and Suweon 287 partitioned more net production to leaf sheaths. Suweon 287 showed good recovery after rewatering and partitioned much assimilates to roots after released from water stress.