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

Abstract

SUMMARY 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.

Estudo anatômico foliar do clone híbrido 4430 de Tradescantia: alterações decorrentes da poluição aérea urbana

“…Segundo Wellburn (1990), tais efeitos variam também em função de vários fatores como a concentração dos poluentes, o tempo de exposição, a idade da planta, fatores edáficos e intensidade luminosa, causando injúrias…”

“…Cabe destacar que os resultados aqui obtidos podem ser uma indicação indireta do efeito da poluição no crescimento da planta e reforçam a idéia de que a poluição afeta o balanço hídrico e, conseqüentemente, a taxa de fotossíntese conforme já registrado para outras espécies (Wellburn 1990, Masuch et al 1992, Viskari et al 2000.…”

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

“…Previous research has shown that at high concentrations, many of the pollutants present in exhaust gases can be damaging to plants (Ackerly & Bazzaz, 1995;Grantz et al, 2003;Wellburn, 1990).…”

Nitrite–dependent nitric oxide production pathway: implications for involvement of active nitrogen species in photoinhibitionin vivo

“…Fumigation with NOx sometimes does not show deleterious e¡ects but it often stimulates plant growth probably acting as a nitrogen fertilizer (Yoneyama et al 1979). There has therefore been controversy as to whether NOx at atmospheric concentrations is phytotoxic (Wellburn 1990). Taylor & Eaton (1966) reported that long exposure to a low concentration of NO 2 suppressed the growth of bean and tomato seedlings.…”

“…Because both NO and NO 2 produce nitrite in an aqueous solution, it has been widely presumed that the toxicity is ascribed to the nitrite toxicity on photosynthesis (Wellburn 1990). Nitrite was reported to acidify the stroma, which may inhibit the enzymatic reactions in the Calvin^Benson cycle (Purczeld et al 1978).…”