Assimilation of nitrogen dioxide in response to fumigation with 15 N-labelled nitrogen dioxide was studied in 217 plant taxa. The taxa included 50 wild herbaceous plants collected from roadsides (42 genera, 15 families), 60 cultivated herbaceous plants (55 genera, 30 families) and 107 cultivated woody plants (74 genera, 45 families). Two parameters, the 'NO 2 -N content', or NO 2 -derived reduced nitrogen content in fumigated plant leaves (mg N g -1 dry weight), and the 'NO 2 -utilization index', or percentage of the NO 2 -derived reduced nitrogen in the total reduced nitrogen, were determined. The NO 2 -N content differed 657-fold between the highest (Eucalyptus viminalis; 6·57) and lowest (Tillandsia ionantha and T. caput-medusae; 0·01) values in the 217 taxa; 62-fold in a family (Theaceae) and 26-fold in a species (Solidago altissima). Nine species had NO 2 -utilization indices greater than 10%, of which Magnolia kobus, Eucalyptus viminalis, Populus nigra, Nicotiana tabacum and Erechtites hieracifolia had NO 2 -N contents > 4·9. These plants can be considered 'NO 2 -philic' because in them NO 2 -nitrogen has an important function(s). The Compositae and Myrtaceae had high values for both parameters, whereas the monocots and gymnosperms had low ones. These findings suggest that the metabolic pathway of NO 2 -nitrogen differs among plant species. The information presented here will be useful for creating a novel vegetation technology to reduce the atmospheric concentration of nitrogen dioxide.

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