Effects of Atmospheric SO2 on the Photosynthetic and Transpiratory Rate of Helianthus annuus L

• Published in: Environment Control in Biology Vol. 11; no. 3; pp. 103 - 108
• Main Authors: OHSHIMA, Yasuo, USHIJIMA, Tadahiro, TAZAKI, Tadayoshi
• Format: Journal Article
• Language: English
• Published: Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists 1973
• ISSN: 0582-4087; 2185-1018
• DOI: 10.2525/ecb1963.11.103

A study was undertaken to make clear the invisible injury of atmospheric sulfur dioxide (SO2) by the effect upon photosynthesis and transpiration of young plants of Helianthus annuus. Thus the variation of photosynthetic and transpiratory rate was measured simultaneously with SO2 concentration and relative humidity for plants in fumigating chambers aerated with the air containing relevant SO2 concentration. The depression rate of photosynthesis and transpiration, i.e., the ratio of the value under SO2 fumigation against that of the control, rose in accordance with the increase of ambient SO2 concentration up to 1 ppm. After SO2 introduction the depression of photosynthesis preceeded that of transpiration, suggesting the decrease of photosynthesis before stomatal closure, whereas the simultaneous recovery of both rates was observed after SO2 removal, though the recovery retarded to some extent in fumigation with higher concentration of SO2. Relative humidity and light condition in the chambers gave little influence upon the depression rate of photosynthesis, while in the shaded plants with shade leaves the depression rate considerably increased in every SO2 concentration. Lastly, SO2 was fumigated for 3 hr every day to see the effect of long term fumigation. After SO2removal every day, photosynthesis soon recovered, though not completely, and the photosynthesis on the next day showed somewhat lower value compared to that of the previous day. When SO2 was fumigated to plants pretreated with 0.3 ppm SO2 for 8 days (8 times of fumigation) the depression rate of photosynthesis was the same with those not pretreated, although the after. effect of long term fumigation appeared in the decrease of photosynthetic rate in normal air.