Photosynthesis and needle elongation response of Pinusstrobus clones to low level sulfur dioxide exposures

Abstract

Sensitive and tolerant eastern white pine (Pinusstrobus L.) clones were exposed to 5.0 ± 0.5 pphm SO2 for 2 h. At the end of the fumigation, the average apparent photosynthetic rate was depressed by 27% in sensitive clones and by 10% in tolerant clones. Regression analysis of rate of reduction in photosynthesis over the 2 h was significant (0.05 level) for both classes, as was the difference (0.01 level) between the levels of the two regressions. Differences in final needle lengths of fumigated tolerant and sensitive clones were not significant.