Impact of atmospheric ammonia on growth, C and N accumulation and photosynthesis of two maize cultivars with different N root supply

Impact of enriched atmospheric NH 3 in combination with low and high N medium on growth, total C and N accumulation (C tot A and N tot A) and photosynthetic characteristics of two maize cultivars i.e. SD19 (cult. 1) and NE5 (cult. 2) with low N and N high use efficiency, respectively, was investigated. Plants were exposed to 10 nl/L and 1000 nl/L NH 3 fumigation, respectively, for 30 days in open-top chambers (OTCs). Under exposure to the low N medium, increase of the atmospheric NH 3 concentration to 1000 nl/L from the ambient level significantly ( P < 0.05) increased dry matter (DM) (by 18% in cult. 1 and 14% in cult. 2 respectively), C tot A, N tot A, net photosynthetic rate (P n ), stomatal conductance (G s ) and apparent quantum yield (AQY) but decreased intercellular CO 2 concentration (C i ) in both cultivars. These effects were more pronounced in cult. 1 as compared to those in cult. 2. In contrast, in the high N solution, enriched atmospheric NH 3 led to a decrease in DM, C tot A, N tot A, P n , G s and AQY but an increase in C i of cult. 2 only. Dark respiration rate remained unaffected by enrichment of NH 3 in each treatment. Therefore, it is concluded that appropriately enriched atmospheric NH 3 can improve plant growth of maize by enhancing C tot A, N tot A, and photosynthesis in the low N medium, especially for low N use efficiency cultivars.