The deposition of atmospheric ammonia and its effects on plants

Abstract

SUMMARY Across Europe, total nitrogen deposition is increasing and, of this total, atmospheric ammonia can contribute up to 50–80%. Average deposition of ammonia in the UK is likely to be around 15–20 kg ha−1 yr−1, while in The Netherlands, which has some of the highest rates of deposition, this value is likely to be between 40 and 50 kg ha−1 yr−1. It is argued that because of the processes of assimilation and nitrification this ammonia is an acidifying pollutant. Ammonia taken up by plants is most likely to be directly assimilated and this uptake can have a strong effect on the nutrient imbalances of the plant. With root uptake in particular, anions are taken up in preference to cations. However, simple soil/plant nutrient measurements are unlikely to be a definitive means of monitoring ammonia pollution. This is because the processes of ammonia metabolism and acidification affect soil ion activity, mycorrhizas, plant uptake, and foliar leaching. These effects interact with acidity per se, and are compounded by the strong correlative co‐deposition of ammonia with sulphur. Evidence for uptake of gaseous and wet deposited ammonia by leaves is presented. The exact mechanism of ammonia toxicity is still not really clear, but could be due to physiological perturbation, rather than to the direct toxicity of the ion. Assimilation of ammonia by leaves releases protons which can cause cellular acidosis, and has important implications for acid‐base regulation in cells. This regulation depends on intrinsic features of the plant's metabolism, that is in turn dependent on the ecology of root versus leaf nitrogen nutrition under normal conditions. Certain species are more acidic in a leaf physiological sense and tend to be prone to damage by pollutants. Likewise, acidic habitats are particularly prone to damage through both eutrophication and the different capacities of plants both to utilize and to buffer against this nitrogen enrichment. The current evidence from The Netherlands suggests that the part this plays in perturbing the ecosystem should not be underestimated.

Effects of different ammoniacal nitrogen sources on N-metabolism of the atmospheric bromeliad Tillandsia pohliana Mez

“…The build-up of free NH 4 + in the plant tissues may not necessarily inhibit photosynthesis or growth on a short-term basis. The acid-base regulation in cells depends on intrinsic features of the plant's metabolism (Pearson & Stewart 1993).…”

“…It is possible that throughfall is rich in NH 4 + as it was observed in forests in the polluted regions of The Netherlands, with concentrations of 0.32 to 2.4 mM (Van Breemen et al 1982). In several European countries, it was observed that 50% of the N compounds released into the environment consisted of NH 3 /NH 4 + , and this indicates the importance of these compounds for vegetation (Pearson & Stewart 1993). Besides being released from the soil, NH 3 can be emitted from senescing plant parts (Hanstein & Felle 1999).…”

Cover versus recovery: Contrasting responses of two indicators in seagrass beds

“…However when nutrients, particularly nitrogen, are in excess, the plant physiological and growth response are negatively affected. This is due to nitrogen toxicity, and in aquatic or marine systems additional algal overgrowth, which both lead to a higher demand of carbon skeletons, thus causing physiological imbalance, ultimately leading to mortality and collapse (Pearson and Stewart, 1993;Marschner, 1995; for seagrasses reviewed in: Touchette and Burkholder, 2000;Burkholder et al, 2007). Along this eutrophication trajectory, prior to collapse, increasing plant cover thus may coincide with increasing physiological imbalance, which likely diminishes plant recovery potential.…”

Effective Room-Temperature Ammonia-Sensitive Composite Sensor Based on Graphene Nanoplates and PANI

“…1 It can even be generally produced in natural processes in animals, human and plants. 2 Ammonia can irritates skin, eyes and respiratory tract of humans when the concentration reaches to a certain value (the safety threshold is ∼25 ppm in air). 3 It is also flammable at concentration of ca.…”