Using sand cultural experiment, the differences of morphological characters and physiological characteristic of roots among 3 oilseed rape cultivars, the relationship between characters and nitrogen use efficiency under two nitrogen supply levels were studied. The results showed that under normal supply nitrogen, the differences of the dry weight, the first lateral root and the total length of roots of 3 oilseed rape cultivars were obvious, while the differences of the vigor, the total absorbing area and active absorbing area of roots were not significant. Under nitrogen stress condition, the ...