Influence of different sulphur dioxide concentrations on four cultivated plant species and on L-malate content, diffusive resistance and 35SO2 uptake of maize leaves

Sulphur dioxide at 0.5 ppm in air caused leaf injury after three days of gassing in sunflower and barley, and after six - in bean. In maize leaf injury became manifest only at much higher concentrations (1.5 and 2.0 ppm). In spite of the much less manifested leaf damage the dry weight yields of maize decreased after exposure to SO2 at 0.5 ppm in a similar manner as in the other experimental species badly injured by gassing. The degree of the harmful effect of SO2 for identical values of the product of concentrations and exposure times depended on the applied gas concentration. In maize sulphur dioxide first produced a drop in the diffusive resistance of leaves but after some days of gassing diffusive resistance rose again. Higher concentrations of SO2 depressed the level of L-malate in maize leaves. The uptake of the 35SO2 by younger leaves of maize was higher and translocation was mainly to leaves higher on the stem and to upper stem parts. (author)