Large amounts of nitrogen (N) enter ecosystems via N deposition. The increased drought stress has incurred serious threats to plant seed germination and seedling growth (SGe-SGr). It is significant to characterize the combined impacts of N deposition and drought stress on SGe-SGr of plants to enable a further explanation of the response mechanism of SGe-SGr to N deposition and drought stress. This study aims to explore the combined impacts of N deposition with a concentration gradient and drought stress (mimicked using PEG 6000) with different levels on SGe-SGr of wheat. N treatment raises seedling growth of wheat mainly due to the increased levels of available N and the decreased level of peroxidation of the cell cytoplasm membrane of wheat. Drought stress declines SGe-SGr of wheat mostly due to the progressively enlarged osmotic pressure triggered by water deficit and the advanced level of peroxidation of the cell cytoplasm membrane of wheat. N treatment regardless of the concentration dramatically mitigates the adverse impacts of drought stress on seedling growth of wheat. This may be owed to the improved competitive ability for sunlight acquisition and leaf photosynthetic area via the deactivation of nutrition limits (wheat can absorb more N nutrients and improve its drought resistance ability) implemented by N addition. This may also due to the down-regulated level of peroxidation of the cell cytoplasm membrane of wheat under the combined N and drought stress. However, the combined treatments of the high level of N supply and light drought stress decline seed germination of wheat. This may be due to the promoted osmotic pressure contributed by the high level of N supply under water deficit. Thus, N deposition mitigates the adverse impacts of drought stress on seedling growth of wheat but aggravates the adverse impacts of drought stress on seed germination of wheat mostly.

大量的氮通过以下途径进入生态系统N沉积。干旱胁迫的加剧已经严重威胁了植物种子的发芽和幼苗的生长（SGe-SGr）。表征N沉积和干旱胁迫对植物SGe-SGr的综合影响具有重要意义，从而能够进一步解释SGe-SGr对N沉积和干旱胁迫的响应机制。本研究旨在探讨不同浓度水平的氮沉降，浓度梯度和干旱胁迫（使用PEG 6000模拟）对小麦的SGe-SGr的综合影响。氮处理提高了小麦的幼苗生长，这主要是由于有效氮水平的提高和小麦细胞质膜过氧化水平的降低。干旱胁迫使小麦的SGe-SGr降低，这主要是由于缺水和小麦细胞质膜过氧化水平的升高导致渗透压逐渐升高。无论浓度如何，氮肥处理都能显着减轻干旱胁迫对小麦幼苗生长的不利影响。这可能是由于提高了获取阳光和叶片光合面积的竞争能力通过取消添加氮来限制营养（小麦可以吸收更多的氮养分并提高其抗旱能力）。这也可能是由于氮和干旱共同作用下小麦细胞质膜过氧化水平的下调。但是，高氮供应和轻度干旱胁迫的联合处理降低了小麦的种子发芽率。这可能是由于缺水下高水平的氮供应导致渗透压升高所致。因此，氮沉降减轻了干旱胁迫对小麦幼苗生长的不利影响，但加剧了干旱胁迫对小麦种子发芽的不利影响。