Emission of NO from several higher plant species

Emission of nitric oxide (NO) from a variety of plant species was observed in a continuously stirred tank reactor. During daytime and at NO concentrations below 1 ppb in the chamber air, NO emissions were observed for all studied nitrate-nourished plant species. A relation was found between the NO emission rates during daytime and the uptake rates of CO 2 . The ratio of the NO emission rate to the CO 2 uptake was similar for all plants. Changes of the net rate of photosynthesis induced by variations of light intensity or changes of CO 2 concentrations changed the NO emission rates correspondingly. The link between NO emissions and CO 2 uptake during daytime allowed estimation of the potential of the vegetation to evolve NO on a global scale as 0.23 Tg N yr -1 . Strong NO emissions during nights were observed when the nitrate concentration in the nutrient solution was enhanced. Then NO emissions were observed with flux densities comparable to the highest emission rates found from soils.