The morphology, especially the root structure, has been of hot concern in uptake and utilization of
N by plants under water deficiency. Root system plays an important role in the uptake of water and
nutrients, synthesis of plant hormones, and the storage of photosynthetic assimilates. Root length,
depth, thickness, density, weight, root to shoot ratio, penetration, osmotic adjustment are all good indicators used for related researches (Luo and Zhang, 2001). Cheng et al. (2007) found that the total root length, density, surface area, and biomass were significantlyhigher in rice cultivars which have higher NUE than those with low NUE and therefore could be used as reliable indicators in high NUE rice cultivar selection. Ye et al. (2010) compared the rice cultivars with different NUE and found that the cultivars with high NUE had higher total root length, surface area, and amount of root apexes than those with low NUE at the full heading stage.