ISHS Acta Horticulturae 381: International Symposium on Natural Phenols in Plant Resistance
DETOXIFICATION OF AIR POLLUTANTS IN THE PRESENCE OF APOPLASTIC PHENOLS |
| Authors: | H. Pfanz, B. Oppmann, P. Wolf, B. Lomsky |
| Keywords: | Apoplast, cell wall, conifers, forest decline, lignin, phenols, sulfur dioxide |
| Abstract:
As a means of forward defense, sulfur dioxide can be oxidized already in the apoplast of leaves. In vitro experiments with isolated intercellular washing fluids (IWF) from leaves of beech, spruce, and barley revealed that besides hydrogen peroxide, phenolic compounds are necessary for sulfite oxidation. In muro, lignin precursors seem to play that role. For spruce needles the KMapp values for sulfite oxidation were 1.74 μM in the presence of coniferyl alcohol, 1.95 μM for caffeic acid, and 93 μM for ferulic acid. Vmax values ranged from 50 to 100 μMole oxygen consumed mg-1 total IWF protein min-1. The KMapp for sulfite was 1.23 (using ferulic acid) and greater than 12.5 mM (all others). In the absence of phenolic compounds, oxidation of sulfite was poor. But in the absence of peroxidases, an autoxidation of sulfite was measurable. Below 2.5 mM sulfite, autoxidation was negligible, but above 4–5 mM sulfite, highly significant autoxidation rates were obtained. | |
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