SO2 effect of photosynthetic activities of intact sugar maple leaves as detected by photoacoustic spectroscopy

Short-term (4 hours) effect of different concentrations of SO2 fumigation on in vivo photochemical activities of sugar maple (Acer saccharum Marsh.) leaves was investigated using photoacoustic spectroscopy. The relative quantum yield of O2 evolution (ratio of O2 signal to the photothermal signal) and photochemical energy storage are increased by 0.05 microliter per liter of SO2. This increase is more pronounced in 5 to 7 year old saplings than in 3 month old seedlings. Both oxygen-relative quantum yield and energy storage of seedlings are inhibited by increased concentrations of SO2 and the inhibition is concentration dependent. The inhibition is greater in seedlings than in saplings at 2 microliters per liter of SO2, indicating the more susceptible nature of seedlings. The present study indicates a concentration dependent differential effect of SO2 on photochemical activities of sugar maple leaves