Physiological and Molecular Response of Wheat Roots to Nitrate Supply in Seedling Stage

The objective of this study was to understand the morphological, physiological, and molecular responses of wheat roots to nitrate supply at seedling stage. Two wheat genotypes, Jimai 22 and Shannong 15, were grown in Hoagland's nutrient solution with different nitrate levels at seedling stage. Results indicated that the plant dry weight and N accumulation increased with the increase of nitrate supply. The number of axial root, total uptake area (TUA), and active uptake area (AUA) increased with more nitrate supply. Correlation analysis indicated that significant positive correlations existed between N accumulation and dry weight, N accumulation and AUA, and N accumulation and AUA/TUA. Although, the expressions of NRT2.1, NRT2.2, and NRT2.3 decreased with nitrate supply increased, the expressions of NRT1, NRT2.1, and NRT2.3 could maintain high level at N3 treatment. The free amino acid and NO3− content in shoot also increased with the increased nitrate application, but no significant difference was found in root among the treatments. These results implied that the increase of N uptake by nitrate supply was due to the morphological and physiological responses of wheat roots and the high expression level of TaNRT genes. Similarly, the contribution of morphological, physiological, and molecular parameters was different between two genotypes of wheat.