How Does Nitrogen Application Ameliorate Negative Effects of Long-Term Drought in Two Maize Cultivars in Relation to Plant Growth, Water Status, and Nitrogen Metabolism?

Abstract

Two maize cultivars, Shaandan 9 (S₉) and Shaandan 911 (S₉₁₁), were investigated to explore the ameliorating effects of nitrogen (N) addition on their growth, water status, and N metabolism under long-term drought stress (DS). Elevated N rate increased dry matter, grain yield, relative water content, nitrate reductase activity, soluble protein concentration, and concentrations of free proline and endogenous glycinebetaine (main contributors to osmoregulation) of both cultivars under DS than control. The responses under DS were more significant for S₉₁₁ than those for S₉, especially at high N rate. Additionally, S₉ maintained greater evaluated parameters than S₉₁₁ with no N addition under DS, and these differences decreased with N application. Correlations were more evident among all parameters under DS than those under control. Thus, moderate N plays an evident physiological role in alleviation of DS effects on plant growth by improving water status and N metabolism, especially for drought-sensitive cultivars.

Keywords:

• Long-term drought stress
• nitrogen fertilizer
• nitrate reductase activity
• osmotic nitrides
• relative water content

Acknowledgments

This work is jointly funded by the National Natural Science Foundation of China, Project No. 30571116; by the China Postdoctoral Science Foundation and Chinese Universities Scientific Fund, Project No. QN2009069; and by the Foundation of State Key Laboratory of Soil Erosion and Dryland Farming, Project No. 10501-J-2.