The primary outcome is the observation that key enzymes of the phenylpropanoid and subsequent flavonoid and lignin biosynthetic pathways are possible targets of Snitrosylation. The polyphenol biosynthesis metabolism generates an enormous collection of secondary metabolites that are involved in plant development and stability, plant defense responses against abiotic, and biotic environmental constraints and signaling. Strikingly, many enzymes belonging to the plant primary carbohydrate metabolism were identified as targets of S-nitrosylation. Snitrosylation of the glycolytic enzyme GAPDH results in a reduction of enzyme activity in animals and plants and is a well known example of how negatively affects the enzyme function. It has been proposed that under oxidative stress, the glycolytic pathway is reduced and glucose equivalents are redirected into the pentose phosphate pathway, which is essential for maintaining the cytoplasmic NADPH concentration as a base for the anti-oxidative defense systems. Our proteomic analysis in poplar revealed that photosynthesis is another important cellular process which is regulated by protein Snitrosylation, supporting observations from previous studies. We observed an Apoptosis Activator 2 increase in the number of Snitrosylated proteins related to photosynthetic processes when comparing green, un-differentiated calli with fully developed poplar leaves. Various members of the photosynthetic light reaction, as well as enzymes of the Calvin cycle, are Snitrosylated under steady-state conditions. In addition to the regulation of photochemical aspects, four enzymes of the tetrapyrrole biosynthetic pathway are S-nitrosylated in poplar: glutamate 1-semialdehyde Ethacridine lactate monohydrate aminotransferase, porphobilinogen synthase, porphobilinogen deaminase and coproporphyrinogen III oxidase. The cumulative ozone uptake in the present experiment was 110619 mmol m22, a value of comparable magnitude also applied in earlier studies. We observed no immediate decrease in net CO2 assimilation and transpiration rates upon ozone treatment, demonstrating that grey poplar tolerates high acute ozone doses, an observation already mentioned before.