Response of maize genotypes with different nitrogen use efficiency to low nitrogen stresses

Objectives

This paper aims to compare the property difference of spatial and temporal distribution of different nitrogen use efficiency maize genotypes and discuss the physiological mechanism of nitrogen efficiency of maize.

Method

In this study, phenotype of root crowns of maize in seedling stage (V5), bell stage (V12) and silking stage (R1) was conducted to discover phenes and phene modules related to N acquisition. An image was captured for the whole roots. Custom software was used to measure root phenes including root area, root projected structure length, maximum width of roots, and root angle. The study was conducted to examine the differences in spatial and temporal distribution of maize root at two nitrogen levels (0 and 240?kg hm-2), high efficiency genotype ZHENGDAN958 (ZD958) and low efficiency genotype DANYU13 (DY13) are used in field production. Under the low nitrogen stress conditions, the root area of ZD958 significantly increased after bell stage and exceeds the CK by 20.2% at silking stage. With LN, the root projected structure length of ZD958 was longer than that of CK by 49.4% at silking stage. The low efficiency genotype DY13 had no obvious change at two nitrogen levels. The number of the grain yield and root system biomass of high efficiency genotype ZD958 was remarkably larger than that of low efficiency genotype DY13.

Conclusion

During the whole growth stage, the root dry weight, root area and the root width med of high efficiency genotype ZD958 were larger than that of high efficiency genotype DY13. Besides, under the low nitrogen stress conditions, the width of ZD958 deep soil root tended to become longer which is good for the nitrogen absorption from the deep soil. High efficiency genotype can construct a root system which is in a well-developed and reasonable spatial distribution before blooming, so as to ensure plant nitrogen absorption and biomass generation as well. The root index of the nitrogen responsivity of high efficiency genotype ZD958 was higher than that of low efficiency genotype DY13 before blooming.