Ambient levels of nitrogen dioxide (NO2) may reduce pollen viability in Austrian pine (Pinus nigra Arnold) trees — Correlative evidence from a field study

A fully randomized sampling design was adopted to test whether pollen viability of Austrian pine (Pinus nigra Arnold) was impacted by NO2 pollution. Spatial strata (500 ⁎ 500 m each) with high (41.9–44.6 µg m− 3) and low (15.4–21.0 µg m− 3) NO2 were selected from a defined population in a small area (236.5 km2, < 200 m range in elevation) in Northern Italy. Pollen viability was measured by means of the Tetrazolium (TTC) test. Analysis of variance by means of a generalised linear model showed that NO2 was a significant factor (P = 0.0425) affecting pollen viability. Within the treatment, no significant differences were detected among replicates. Within each replicate, sampling unit data were significantly different (P = 0.000) and this suggested some improvement in the applied sampling design was needed. Pollen viability was significantly related to pollen germination (P < 0.01) and tube length (P < 0.01). This suggested a possible impact of NO2 on the regeneration of Austrian pine in polluted environments.