Biological response of different cultivars of millet to low nitrogen stress

A solution culture experiment was carried out to study the biological trait, the different responses in N uptake and utilization efficiency of four cultivars of millet under low nitrogen stress, the correlation between N uptake and morphological and physiological traits of root system were also discussed. The results show that under low nitrogen stress, the shoot growth of millet was restrained earlier than roots. The N uptake was decreased, but the general efficiency of N increased drastically. The mildest restrain in plant height, leaf area, shoot and root dry weight, total root length, root number, total and active uptake area was in cultivar Jinshu 7. The total N uptake of Jinshu 7 was 1.35, 1.50, 1.39 times of those of Jinshu 1, Jinshu 5, Jinshu 8, accordingly, its N efficiency was 20.92%, 12.44%, 14.83% of the other three cultivars respectively. The increase of the percentage of root N uptake and the decrease of shoot N uptake to total N uptake in Jinshu 7 was 9.75% and 3.47% respectively, which was also smallest among the cultivars tested. Therefore, Jinshu 7 was identified as the typical cultivar tolerant to low nitrogen stress. The results also showed a significant positive correlation between total N uptake and dry weight, length, total and active uptake area in roots under low nitrogen stress, this correlation dose not exist under high nitrogen, indicating that the morphological and physiological traits of root system plays a vary important role in N uptake under low nitrogen stress.