Growth impact of O 3, NO 2 and/or SO 2 on Platanus occidentalis

Abstract

Seedlings of two half-sib families of American sycamore were exposed to 0.05 ppm O 3, 0.10 ppm NO 2, and/or 0.14 ppm SO 2 for 6 h/day for 28 consecutive days. The treatments were O 3, NO 2, SO 2 (each used alone), O 3 + SO 2, O 3 +NO 2, and O 3 + NO 2 SO 2. Significant growth suppressions were noted for both families when exposed to O 3 + SO 2 or O 3 + SO 2 + NO 2. The O 3 + SO 2 treatment had a more significant effect than O 3 alone, and adding NO 2 to the O 3 + SO 2 treatment further suppressed height growth significantly. A 45% and 34% growth suppression was observed for the two families (16-Syc-19 and 16-Syc-23), respectively, in response to the three pollutants in combination. The height growth of both families was significantly suppressed by O 3 alone in some cases. Both families exhibited significant height growth recovery 2 weeks after removal of the pollutant stress. Pollution-induced foliar injury was never evident on the seedlings.