Increased Ammonium Enhances Suboptimal-Temperature Tolerance in Cucumber Seedlings

Area of Science:

• Plant Physiology
• Agricultural Science
• Environmental Stress Biology

Background:

• Nitrate nitrogen (NO₃^--N) is standard for cucumber cultivation.
• Partial substitution with ammonium nitrogen (NH₄⁺-N) can improve nitrogen use, but its effect under cold stress is unknown.

Purpose of the Study:

• To investigate how ammonium uptake and metabolism influence cold tolerance in cucumber seedlings.
• To determine optimal ammonium ratios for cucumber growth under suboptimal temperatures.

Main Methods:

• Cucumber seedlings were exposed to suboptimal temperatures with varying ammonium ratios (0%, 25%, 50%, 75%, 100%) for 14 days.
• Evaluated growth, root activity, protein, proline, and MDA content.
• Analyzed gene expression related to nitrogen transport, metabolism, and root function.

Main Results:

• A 50% ammonium ratio promoted growth, root activity, protein, and proline content while reducing MDA.
• Upregulated nitrogen uptake/transport genes (CsNRT1.3, CsNRT1.5, CsAMT1.1) and metabolism genes (CsGOGAT, CsGS).
• Upregulated PM H⁺-ATPase genes (CSHA2, CSHA3) in roots, enhancing nitrogen transport and membrane stability.

Conclusions:

• Supplementing with 50% ammonium nitrogen enhances cucumber seedling tolerance to suboptimal temperatures.
• Improved tolerance is attributed to enhanced nitrogen assimilation in roots, driven by specific gene expression.
• Findings suggest a strategy for improving crop resilience in cold environments.