Impact of ozone and sulfur dioxide on net photosynthesis of hybrid poplar cuttings

Abstract

Softwood cuttings of hybrid poplar clone No. 207 (Populusdeltoides Bartr. × Populustrichocarpa Torry and Gray) were fumigated with either charcoal-filtered air (control), 0.5 ppm SO2, or 0.5 ppm SO2 + 0.25 ppm O3 for 12 h each day for 3 weeks. The net photosynthetic rate and CO2 compensation point were then measured in a closed-loop gas assimilation system with an infrared gas analyzer. Net photosynthesis was measured at light intensities of 430 and 730 μE•m−2•s−1 (photosynthetically active radiation) and in CO2 concentrations of 300, 500, and 1000 ppm. Net photosynthesis increased with an increase in light intensity and CO2 concentration but was significantly reduced by the SO2 + O3 treatment. The leaves were classified into five groups on the basis of visible injury. There were no significant differences in the net photosynthetic rates among uninjured leaves in the three fumigation treatments. However, analysis of the data from the SO2 + O3 treatment, which separated the leaves into injury classes, showed that the CO2 – injury class interaction was significant. At 300 ppm CO2, there were no significant differences in the net photosynthetic rates among the five injury classes. At 500 and 1000 ppm CO2, there were significant differences in the photosynthetic rates between leaves without visible injury and those with injury. Photosynthesis in the injured leaves may have been suppressed by an increase in the respiration rate and a decrease in the photosynthetic area. The increased respiration rate is suggested by the CO2 compensation point data that was significantly higher in all of the fumigated leaves. There were no significant differences in the chlorophyll content of the leaves from the three treatment groups.

Regional tree growth reductions due to ambient ozone: evidence from field experiments

“…In previous studies (19), statistically significant reductions in biomass production, 12-24%, were measured for P. tremuloides in 1982 and 1983 at the same site using similar techniques. These observations from field studies of growth reductions resulting from ambient ozone are consistent with the large body of laboratory and greenhouse research indicating the susceptibility of Populus to ozone concentrations below 235 Mg 3, including studies showing reduced growth (20-24) and lower photosynthetic rates (7,25,26).…”

Physiological effects of sulphur dioxide. 1. The effect of SO2 on photosynthesis and stomatal regulation of Vicia faba L.

“…From Table 3 it appears that bolh the CO2 eompensation point and the mesophyll resistanee inereased after SO 2 fumigation. An increase in the CO2 eompensation point was also reported by Furukawa, Natori & Totsuka (1980) and Jensen & Noble (1984). This inerease in F indieates that the elTect of SO2 on CO2 assimilation eannot be explained by an equal competitive efTeet of sulphur tnelabolites with respeet lo CO2 and O2.…”

Physiological effects of sulphur dioxide. 1. The effect of SO2 on photosynthesis and stomatal regulation of Vicia faba L.

“…From Table 3 it appears that both the C0 2 compensation point and the mesophyll resistance increased after S0 2 fumigation. An increase in the C0 2 compensation point was also reported by Furukawa, Natori & Totsuka (1980) and Jensen & Noble (1984). This increase in r indicates that the effect of S0 2 on C0 2 assimilation cannot be explained by an equal competitive effect of sulphur metabolites with respect to C0 2 and 0 2 • The observed increase in the C0 2 compensation point and mesophyll resistance can only be explained by a stronger effect of sulphur compounds on the affinity of the enzyme for C0 2 (Kc) than on its affinity for 0 2 (K 0 ).…”