Analyses of plant injuries due to harmful gases. Part I. Section E. Experiments on the effects of ozone and sulfur dioxide on Mulberry trees

Seedlings of a 1-year cutting of mulberry trees were exposed to ozone, ozone then sulfur dioxide, sulfur dioxide then ozone, and sulfur dioxide then ozone and further sulfur dioxide, the concentrations of ozone and sulfur dioxide being respectively 0.15-0.28 ppm (on the average 0.2 ppm) and 1 ppm. The period of each exposure was 6 hr in the daytime. No visible injury was observed on all the treated trees. The sulfur content of the leaves of treated trees, notwithstanding their position, increased by exposure to SO/sub 2/. The amount was larger as the period of exposure was longer. The sulfur content of leaves of the trees exposed to ozone before exposure to SO/sub 2/ was larger than that of the trees exposed to ozone after exposure to SO/sub 2/.