Effect of sulfur dioxide and sulfite on photochemical energy storage of isolated chloroplasts--a photoacoustic study

Air pollutants effect on monoterpenes composition and foliar chemical parameters in Schinus areira L

Monoterpenes, pigments, lipid peroxidation products, sulfur and water content expressed as dry weight/fresh weight ratio were measured in leaves of Schinus areira L. collected in Mendoza, Argentina. The sampling sites showed different SO(2), NO(2) and PM(10) levels, which allowed setting out zones by mapping. Foliar chemical parameters in S. areira were analysed in relation to these zones. High hydroperoxy conjugated dienes (HPCD) and alpha-phellandrene content in foliar samples coming from areas with high SO(2) levels were measured. Principal component analysis (PCA) showed a positive association among SO(2), HPCD, malondialdehyde, sabinene and beta-pinene. In relation to NO(2) levels high values of chlorophyll (Chl)-b and Chl-b/Chl-a ratio were found. PCA showed for NO(2), an association with Chl-b/Chl-a, phaeophytin-a/Chl-a ratios and alpha-phellandrene. As regard PM(10), no significant differences were found in the chemical parameters indicating foliar damage, whereas the contents of tricyclene, alpha-pinene and beta-pinene showed low values in the area with high levels of this pollutant. From the results, it can be inferred that the more noticeable changes in the foliar chemistry of S. areira were detected in relation to the different SO(2) levels. This response was associated to an increase in the foliar oxidation processes accompanied by modifications in the levels of terpenes. This is important, as SO(2) was the only pollutant whose values in the annual arithmetic mean were over the standard value of 30 ppb.

Sulfite inhibition of photochemical activity of intact pea leaves

Sulfite treatment of pea leaf disks in light caused a significant decrease in the relative quantum yield of photosynthetic oxygen evolution and energy storage (ES) as measured by photoacoustic (PA) spectroscopy. The inhibition was concentration dependent and was less in darkness than in light, indicating light-dependent inhibitory site(s) on the photosynthetic electron transport chain. Further, in darksulfite-treated leaves, the energy storage was more affected than the relative quantum yield of oxygen evolution, suggesting that photophosphorylation and/or cyclic electron transport around PS I are sites of sulfite action in darkness. The Rfd values, the ratio of fluorescence decrease (fd) to the steady-state fluorescence (fs), decreased significantly in leaves treated with sulfite in light but were not affected in dark-treated ones, confirming the photoacoustic observations. Similarly, the ratio of variable fluorescence (Fv) to maximum fluorescence (Fm), a measure of PS II photochemical efficiency, was affected by sulfite treatment in light and not changed by treatment in darkness. An attempt was made to explain the mechanism of sulfite action on photosynthetic electron transport in light and in darkness.