Volatile hydrocarbons from photosynthetic membranes containing different fatty acids

Effect of high irradiance and iron on volatile odour compounds in the cyanobacterium Microcystis aeruginosa

The cyanobacterium, Microcystis aeruginosa was exposed to direct sunlight for 3, 6 or 9 h in media containing either low or high concentrations of iron, in order to determine any effects on the composition of volatile odour compounds (VOCs) released under photooxidative conditions. The most abundant VOCs detected included aliphatic hydrocarbons (C15-C21), naphthalene and the terpenoid compounds, beta-cyclocitral, and beta-ionone. Exposure to sunlight and low iron concentrations resulted in a decrease in beta-cyclocitral, beta-ionone, heptadecane and the total VOCs concentration after 9 h with respect to the control cultures. Six VOCs detected in the low iron cells were not detected in any of the high iron cells. However, those VOCs present in the high iron cells, in general, occurred at higher concentrations than the equivalent low iron cells after exposure to the sunlight conditions. Consequently, it was concluded that exposure to both high irradiance and high iron concentrations influenced the VOCs composition in cyanobacteria and this was interpreted to represent a cellular change during the photooxidation-promoting conditions.

Peroxidative processes induced in bean leaves by fumigation with sulphur dioxide

Bean plants have been fumigated for 1 h with 300 or 1000 nl litre(-1) SO(2). Dependent on the SO(2) concentration, we observed an evolution of ethane the leaves. Even with 1000 nl litre(-1) SO(2) the evolution lasted for only 4 h. Pretreatment of single leaves with the radical scavenger ethoxyquin prevented this SO(2)-induced ethane formation. Another indication for the initiation of radicalic peroxidative processes by SO(2) was obtained by the manipulation of the endogenous antioxidants vitamin C and glutathione. An increase of both compounds by application of precursors of both biosynthetic pathways could completely suppress peroxidative ethane evolution. We also found a very good quantitative correlation between endogenous glutathione and ethane formation after SO(2) treatment. During these peroxidative processes, several cell components like fatty acids, chlorophylls, carotenoids and vitamin C were decreased. Based on our results, a mechanism for SO(2) induction of radical reactions leading to peroxidation and the role of endogenous antioxidants are discussed.