Atmospheric N deposition alleviates the unfavorable effects of drought on wheat growth

Drought and atmospheric nitrogen deposition (AND) become increasingly serious in recent decades owing to the progressively rising anthropogenic activities. Thus, it is significant to assess the effects of combined drought and AND on plant morphological and physiological performance (MorPhyPer) to better elucidate the mechanisms that drive the successful plant life-history strategies under the combined drought and AND. The objective of this study is to evaluate the combined drought [imitated by polyethylene glycol-6000 (PEG 6000) solution] with different degrees and AND [a mixed N with a 1: 1: 1 ratio of NH 4 –N: NO 3 –N: CO(NH 2 ) 2 –N] with different concentrations on MorPhyPer of wheat ( Triticum aestivum L.) via the garden-pot cultivation under the condition with natural light for nearly sixty days. Results showed that drought dramatically reduced MorPhyPer of wheat. This phenomenon may be attributed to the gradually enhanced osmotic pressure generated by the dehydrated condition, the enhanced degrees of reactive oxygen species, the raised level of plant cell cytoplasm membrane peroxidation, and/or the downgraded plant enzymatic defensive ability. AND notably improved MorPhyPer of wheat mostly owing to the relieved N deficiencies. The combined drought and AND antagonistically affect plant supporting ability, leaf photosynthetic area, and belowground growing competitiveness of wheat. The reason may be due to the increased belowground moisture content under the combined drought and AND which can improve the efficiency and capacity of nutrients absorption (mainly absorb more N nutrients) by root and transport to the aboveground portion and subsequently raise the level of drought resistance. The reason may be also attributed to the enhanced leaf photosynthetic area which can capture more sunlight and increase the tolerance to the adverse environment. Accordingly, AND notably alleviated the unfavorable effects of drought on MorPhyPer of wheat basically.