Absorption and Translocation of Sulfur Dioxide by Seedlings of Four Forest Tree Species

Abstract

Abstract Rates of absorption of SO 2 and of translocation of absorbed sulfur were determined in sugar maple ( Acer saccharum Marsh.), bigtooth aspen ( Populus grandidentata Michx.), white ash ( Fraxinus americana L.), and yellow birch seedlings [ Betula alleghaniensis Britton ( Betula lutea Michx. f.)]. Bigtooth aspen, a sensitive species, had the highest absorption rate with no prefumigation and sugar maple, a tolerant species, had the lowest. After 20 hours or more of prefumigation with 1,965 µ g/m 3 (0.75 ppm) SO 2 , the rate of sulfur absorption was reduced in all species except white ash, a species intermediate in sensitivity. The relationship between species sensitivity and absorption rate thus changed with the prefumigation treatment. The foliar sulfur content of all species increased with SO 2 fumigation. Sulfur‐35 absorbed from the atmosphere as 35 SO 2 was concentrated mainly in the leaves shortly after fumigation, but by the eighth day had been translocated throughout the plants. Amounts of sulfur translocated to roots varied with species.