Atmospheric pollution by the oxides of nitrogen, NO and NO2 , can cause reductions in growth but rarely visible injury. This review considers their uptake into foliage, as well as their subsequent metabolism and physiology, and attempts to explain why these gases are often phytotoxic. The combined stresses of resisting cellular acidification, enhanced levels of nitrite (and ammonia), and the direct interference of the free radical ('N=O) with critical enzymes, reaction centres and regulatory mechanisms are thought to be the main reasons why oxides of nitrogen, especially NO, inhibit growth. If other air pollutants such as SO2 are also present with NO or NO2 then free radical-induced injury, similar to that caused by O3 alone, also occurs. CONTENTS Summary 395 I. Introduction 396 II. Uptake and cycling of oxides of nitrogen 396 III. Biochemical responses to NO and NO2 405 IV. Physiological responses to NO and NO2 410 V. Combinations of NO and NO2 with other pollutants 416 VI. Recapitulation and beyond 418 Acknowledgements 420 References 420.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1990.tb00467.x

Tansley Review No. 24 Why are atmospheric oxides of nitrogen usually phytotoxic and not alternative fertilizers

Dry deposition of reactive nitrogen compounds: A review of leaf, canopy and non-foliar measurements

Responses of herbaceous plants to urban air pollution: effects on growth, phenology and leaf surface characteristics.

This book reports on the knowledge of the sensitivities and responses of forests, wetlands and crops to airborne pollutants. Pollutants examined include: acidic depositions, heavy metal particulates, sulphur dioxide, ozone, nitrogen oxides, acid fogs, and mixtures of these. Various types of ecosystem stresses and physiological mechanisms pertinent to acid deposition are also discussed. Related subjects, such as the effects of ethylene on vegetation, the physiology of drought in trees, the ability of soils to generate acidity naturally, the role of Sphagnum moss in natural peatland acidity, the use of lichens as indicators of changing air quality, and the magnitude of natural emissions of reduced sulphur gases from tropical rainforests and temperate deciduous forests, are covered.

https://www.cell.com/trends/ecology-evolution/pdf/0169-5347(88)90110-3.pdf

Effects of atmospheric pollutants on forests, wetlands, and agricultural ecosystems

SUMMARY
Atmospheric nitrate deposition varies across Northern Britain, and has increased approximately fourfold since the last century in the Manchester Region. Ombrotrophic mires depend on an atmospheric supply of elements, and some components of nitrogen deposition at two mire sites in northern Britain were investigated. The sites differed in proximity to major pollution sources. Growth of Sphagnum cuspidatum Hoffm, in bog pools was less in the polluted site and this was associated with a marked increase in tissue nitrogen concentration. Field experiments in which S. cuspidatum plants from unpolluted sites were exposed solely to atmospheric deposition in artificial bog pools showed that much of this large increase in nitrogen concentration could have resulted from atmospheric deposition alone. Concentrations of nitrate and ammonium within the range observed in bulk deposition at the polluted site reduced the growth of S. cuspidatum in a laboratory experiment. The results are discussed in relation to a general increase in atmospheric nitrogen deposition, and its potential importance to plant growth.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1986.tb00595.x

R.M. Law

Papers

5 – oxides of nitrogen and the greenhouse atmosphere