Gas Alert: The NO2 Pitfall during NO Fumigation of Plants

Physiological functions of nitric oxide (NO) in plants are often investigated by using chemical NO donors (Feelisch, 1998; Floryszak-Wieczorek et al., 2006) or fumigation of plants with NO gas (Huang et al., 2004; Palmieri et al., 2008; Vitor et al., 2013; Frungillo et al., 2014; Kasten et al., 2016; Krasuska et al., 2016; León et al., 2016; Melo et al., 2016). Treatment with gaseous NO has the advantage of being non-invasive and timeas well as cost effective. However, NO can react with airoxygen resulting in the rise of toxic nitrogen dioxide (NO2; Groß et al., 2013; Heinrich et al., 2013). In human medicine NO2 formation is a well-established risk factor during NO inhalation as a cure against pulmonary diseases (Schedin et al., 1999; Sokol et al., 1999). The damaging effect of NO2 on plants has been frequently demonstrated (Wellburn, 1990; Xu et al., 2010; Liu et al., 2015; Kasten et al., 2016). In this current opinion article fumigation approaches were critically re-evaluated with a special focus on contaminations of NO-enriched air with NO2. Potential artifacts and data misinterpretation due to unintended co-treatment of plants with both gases are highlighted.