Does nitrate fertilization induce nox emission from scots pine (p. sylvestris) shoots?

Abstract

Aims The possibility of NOx (NO + NO2) emissions from plants and the underlying mechanisms are still under discussion. Excess NO created possibly as a result of nitrite accumulation in plant leaves has been suggested to result in emissions. Such emission has been observed in laboratory conditions due to nitrate fertilization. In this study, we tested whether nitrate fertilization of Scots pine seedlings growing outdoors leads to accumulation of NO3-or NO2-in the needles and subsequent NOx emission. Methods The experiment was done at the SMEAR II station in Southern Finland. The seedlings received nitrate or ammonium fertilizer or neither. Shoot NOx emissions were measured with dynamic chambers. Total dissolved nitrogen, inorganic nitrogen, NO3-, NO2-and NH4+ concentrations in the soil and needles were determined. Results NOx fluxes from the shoots were, on average, deposition. There was no indication of fertilizationinduced NO or NOx emissions. The highest NO fluxes were observed at night and were humidity-related. Conclusions It seems unlikely that additional nitrate in the soil could cause significant NOx emission from boreal Scots pine forests in field conditions, possibly because of soil chemistry.

Laboratory measurements of stomatal NO<sub>2</sub> deposition to native California trees and the role of forests in the NO<sub><i>x</i></sub> cycle

“…Some past work has demonstrated that UV light may cause photolysis of nitrate at the leaf surface and subsequent emission of NO x (Hari et al, 2003;Raivonen et al, 2006). The lack of a relationship between NO x emission and soil N fertilization contrasts with the results of Teklemmariam and Sparks (2006), but is consistent with the nitrogen fertilization experiments conducted by Joensuu et al (2014).…”

“…For example, Chen et al (2012) observed an increase in NO emission and Teklemmariam and Sparks (2006) detected an increase of NO 2 emission under conditions of elevated soil nitrate. Per contra, Joensuu et al (2014) found no evidence of fertilization-induced NO x emissions.…”

“…CC BY 4.0 License. studies which have also found a negligible impact of nitrogen fertilization on NO 2 uptake (Teklemmariam and Sparks, 2006;Joensuu et al, 2014). This suggests that the mechanism of NO 2 uptake via dissolution and subsequent reduction of NO − 3 and NO − 2 is likely not bidirectional, nor influenced by accumulation of NO − 3 and NO − 2 within the mesophyll.…”

“…No influence of soil nitrogen on either NO 2 or NO uptake has been documented at atmospherically relevant conditions (Okano and Totsuka, 1986;Teklemmariam and Sparks, 2006;Joensuu et al, 2014).…”

Laboratory measurements of stomatal NO<sub>2</sub> deposition to native California trees and the role of forests in the NO<sub>x</sub> cycle

“…The most divisive example of the mesophyll quandary is the sometimes-reported emission of NO x from plants, mostly in the form of NO, at low NO x mixing ratios that would be relevant to remote forested regions (Johansson, 1987;Rondón and Granat, 1994;Hereid and Monson, 2001;Sparks et al, 2001;Teklemmariam and Sparks, 2006). This would, under many conditions, indicate that trees instead serve as a constant source, rather than sink, of NO x .…”