Abstract
When the mulberry trees were exposed to sulfur dioxide, many spots of oil-soaked aspect or of brownish-red color appeared frequently at the interveinal parts of the mature leaves, and sometimes at the edge and marginal parts of the newly sprouted leaves and the senility leaves.
The symptoms of damage appeared in about 82hr following the exposure to 1ppm gas and in about 28hr following exposure to 2ppm gas. The amount of intake of sulfur in the leaves at the time point of appearance of the damage was about 0.49% per dry weight in case of 1ppm of gas concentration and about 0.4% in case of 2ppm. The appearance of damage, depended more on gas concentration than on the exposure time. When exposed to a gas of high concentration, the damage occurred by the intake of a relatively small amount of sulfur.
No bad effect was observed when silkworm larvae were fed with exposed leaves in which the amount of intake was below 0.2% per dried matter (0.4% in the total amount added 0.20 of sulfur originally contained in the leaves), but when the amount exceeded 0.30 (0.5% in the total amount of sulfur), bad effects appeared in the growth, health degree, cocoon quality etc. The larvae showed symptoms such as slow growth, loss of weight, body shrinks etc.
