Options
1998
Journal Article
Titel
Organic and inorganic sulfur transport in the xylem sap and the sulfur budget of Picea abies trees
Abstract
Temporal changes in inorganic and organic sulfur compounds (sulfate, glutathione, cysteine methionine) were analyzed in xylem sap of 40-year-old Norway spruce (Picea abies (L.) Karst.) trees growing on acidic soils at a healthy and a declining stand in the Fichtelgebirge (North Bavaria, Germany). Studies were carried out (1) to quantify glutathione (GSH) transport in the xylem of spruce, (2) to study the significance of reduced sulfur versus sulfate (SO4(2-)) transport in the xylem, and (3) to compare total sulfur (S) transport in the xylem with the amount of foliar uptake of SO2 in an air-polluted environment. Glutathione was the main reduced S compound in the xylem ranging in concentration from 0.5 to 5 my mol 1(exp - 1). Concentrations of inorganic SO4(2-) in the xylem sap were up to 50 times higher than those of GSH ranging from 60 to 230 my mol 1(exp-1). During the growing season, concentrations of all S compounds in the xylem were highest in May (up to 246 my mol 1(exp -1) and de creased during summer and fall (up to 21 my mol 1(exp -1)). On average, SO4(2-) concentrations in xylem sap were 30 per cent higher at the declining site compared with the healthy site. Diurnal changes in organic S compounds were significant for GSH and cysteine with high concentrations during the night and low concentrations during the day. Diurnal changes in inorganic SO4(2-) concentrations were not significant. Xylem sap concentrations of SO4(2-) and cysteine were twice as high and GSH concentrations were tenfold higher in surface roots than in branches. At both sites, transport of organic S was (up to 3 per cent of total S) compared to transport SO4(2-) . Annual transport of total S in the xylem (SO4(2-) was the main component) ranged from 60 to 197 mmol tree(-1) year(-1) at the healthy site and from 123 to 239 tree(-1) year (-1) at the declining site. Although gaseous uptake of SO2 was estimated to be similar at both sites (38 mmol tree(-1) year(-1); Horn et al. 1989), the ratio b etween annual gaseous uptake of SO2 and transport of S in the xylem was 1:4 and 1:5 at the healthy and declining sites, respectively.
Language
English