Effects of controlled levels of sulphur dioxide on western wheatgrass in a south-eastern Montana grassland.
Swards dominated by western wheatgrass (Agropyron smithii) at 2 sites in SE Montana were continuously fumigated with 2, 4 or 7 p.p.h.m. SO2 from mid-May to Oct. 1975 and from April to Oct. 1976. SO2 stimulated leaf growth by increasing the number of leaves/plant. The response was related to both the conc. of SO2 and the period of exposure. Leaves senesced more rapidly at higher SO2 conc. SO2 treatments did not significantly alter the net production of above-ground parts, the growth rates of above-ground parts and NAR, nor did they affect the leaf area ratios of either western wheatgrass or the entire community. The effects of SO2 on leaf growth and the N:S ratios in plant material indicated that there may be S deficiency in the grasslands studied.