Genotype 478 had a larger root system and absorbed more N than Wu312, especially under low N supply (Wang et al., 2004), and had also larger shoot than Wu312 (Chen, 2001 and Wang et al., 2004). On the other hand, Wu312 had always higher N concentration in plants than 478, no matter whether they grew under N-deficient or N-sufficient conditions (calculated according to the results in Wang et al., 2004)