However, the values of the SPAD reading for ear leaves of both genotypes from the end of silking until the maturity were identical (Fig. 4), and the leaf senescence in 478 was even more rapidly than that in Wu312 (Fig. 1). The results suggested that the difference in NUE between 478 and Wu312 was not due to the difference in duration of green leaf areas, but due to the difference in shoot growth potential. High shoot growth potential and thus high shoot demand for N drove high
root uptake rate of N