Effects of nitrogen on growth, root morphological traits，nitrogen uptake and utilization efficiency of maize seedlings

Based on water culture, the hybrid maize of high yield is selected to study the effects of nitrogen on seedling growth, root morphological traits and nitrogen uptake and physiological N use efficiency. Results show that with N concentrations increasing in a certain range, shoot biomass of four maize cultivars and root biomass of Dongdan 90 (DD90) and Shenyu 21 (SY21) are increased, whereas root growth is inhibited under the high nitrate level, that led to the decrease of root/shoot ratio. The decreased ratio of shoot biomass of Zhengdan 958 (ZD958) is higher than that of root biomass under the high nitrate level (8.0 mmol/L), as a result, the root/shoot ratio of ZD958 is increased. Under different N concentrations, DD90 has better root morphology to improve the ability of N uptake, therefore the N accumulation is increased. With the increase of nitrogen concentration, the N uptake efficiency is increased, while the physiological N use efficiency is decreased in the four hyrid maize. At both lower and higher N rates, ZD958 and DD90 both have higher N uptake efficiency and lower physiological N use efficiency compared with SY21 and Haoyu12 (HY12). The responses of different maize cultivars to nitrogen are significantly different. There are the high tolerance and high N uptake to low nitrogen level in DD90 and ZD958. ZD958 has relatively weak resistance to high nitrogen level. SY21 and HY12 have high nitrogen demands and low nitrogen tolerance. The appropriate N supply could coordinate the growth of root and shoot, advance the root morphology and increase contact root area to nitrogen and nitrogen uptake.