ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Hydroponically grown pea plants (Pisum sativum L., cv. Kleine Rheinländerin) and barley seedlings (Hordeum vulgare L., cv. Gerbel) were fumigated for several days with 1 or 2 μl l−1 SO2. Both species accumulated sulfate during fumigation, although the nutrient medium lacked sulfate. In pea, SO2-dependent sulfate accumulation in different plant parts accounted for 60 percent of the SO2 sulfur which, as calculated from a determination of boundary and stomatal flux resistances had entered the leaves. Up to 55% of the air-borne sulfate was translocated from pea leaves to roots during the period of fumigation, but no or only little sulfate was excreted into the nutrient solution. In contrast, barley retained sulfate in the leaves, and sulfate translocation from shoot to the root system could not be observed. In both species, protons were excreted by the roots. In fumigated plants, proton loss was higher than in untreated controls in pea, but not in barley. In pea, SO2-dependent proton loss into the medium accounted for up to 50% of the sulfuric acid formed from SO2. Proton excretion was strongly dependent on potassium availability in the nutrient medium. Cation uptake by the plants during fumigation was sufficient to compensate for proton loss, suggesting proton/cation exchange at the interface between root and medium. We conclude that by oxidation to sulfuric acid, plants are capable of detoxifying SO2 taken up by the leaves. Depending on plant species, either both protons and sulfate anions can be exported from the leaves, or the proton load on leaf cells can be relieved by proton/cation exchange at the plasmalemma. Finally, the problem of airborne plant acidification may be solved by proton/cation exchange at the level of roots. The burden of acidification is then shifted from the plant to the nutrient medium. Appreciable amounts of sulfate can be excreted neither by pea nor by barley plants.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1993.tb08791.x
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