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 NH3 in combination with low and high N medium on growth, total C and N accumulation (CtotA and NtotA) and photosynthetic characteristics of two maize cultivars, i.e. SD19 (cult. 1) and NE5 (cult. 2) with low and high N use efficiencies, respectively, was investigated. Plants were exposed to 10 nl/L and 1000 nl/L NH3 fumigation, respectively, for 30 days in open-top chambers (OTCs). Under exposure to the low N medium, increase of the atmospheric NH3 concentration to 1,000 nl/L from the ambient level significantly increased dry matter (DM, by 18% in cult. 1 and 14% in cult. 2, respectively), CtotA, NtotA, net photosynthetic rate (Pn), stomatal conductance (Gs) and apparent quantum yield (AQY) but decreased intercellular CO2 concentration (Ci) 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 NH3 led to a decrease in DM, CtotA, NtotA, Pn, Gs and AQY but an increase in Ci of cult. 2 only. Dark respiration rate remained unaffected by enrichment of NH3 in each treatment. Therefore, it is concluded that appropriately enriched atmospheric NH3 can improve plant growth of maize by enhancing CtotA, NtotA, and photosynthesis in the low N medium, especially for low N use efficiency cultivars.