Effects Of Water Deficit On Yield And Water Uptake

Large amount of water is consumed in rice production, which causes serious water shortage in our country. Four rice genotypes i.e. Zhenshan97, N19, IRAT109and N11were used to identify the effects of water deficit on yield and water uptake under well watered and water deficit treatments in our study. N19had the QTL for root depth, and N11had the QTL for root volume.The objectives of this study were:(1) to examine the effects of water deficit on grain yield and yield components in rice,(2) to identify the effects of water deficit on uptake pathways. The following results were obtained:1. Grain yield and yield components decreased under water deficit treatment. Average relative yield (yield under water defcit/yield under well watered) across the two years for IRAT109and N11were0.63and0.69, and Zhenshan97and N19were0.30and0.35. There was a significant difference between two groups of genotypes.2. Root growth decreased under water deficit treatment. The decline of root dry. weight in four genotypes across the two years i.e. Zhenshan97, N19, IRAT109, and N11was50.66%,32.62%,23.87%and14.68%under water deficit compared with well watered treatment.3. Total water uptake rate decreased under water deficit treatment. Contributions of rates of apoplastic pathway and cell-to-cell pathway to total water uptake rate were different among four genotypes. Water deficit significantly altered pathways for water uptake in four genotypes. The proportion of rate of apoplastic pathway to total water uptake rate decreased under water deficit in Zhenshan97and N19, and increased in IRAT109and N11. On the other hand, the proportion of rate of cell-to-cell pathway increased in Zhenshan97and N19, and decreased in IRAT109and N11.4. Root porosity and lignification of parenchyma cell walls increased under water deficit treatment compared with well watered treatment. Root porosity in Zhenshan97and N19were higher than55%under water deficit treatment. There were significantly negative correlations of root porosity with total water uptake rate, water uptake rate by apoplastic pathway and water uptake rate by cell-to-cell pathway. It suggested that the increases of root porosity may decrease the water uptake in rice.5. The expression of OsPIP2;4increased in three genotypes under water deficit treatment compared with well watered treatment, except for N11. The expression of OsPIP2;5increased in Zhenshan97and N19, and decreased in IRAT109and N11under water deficit. However, the changes of gene expression was not reflected at the protein level of OsPIP2;5in this study. Moreover, there were significant differences in water uptake rate by cell-to-cell pathway under water deficit in four genotypes compared with well watered. It means that plant water uptake was regulated by other factors besides aquaporins.