Inhibition of photosynthesis, acidification and stimulation of zeaxanthin formation in leaves by sulfur dioxide and reversal of these effects

Abstract

Abstract.Leaves of Pelargonium zonale L. and Spinacia oleracea L. were fumigated with high concentrations of SO2 for very short periods of time with the aim of first producing acute symptoms of damage and then observing repair. The response of different photosynthetic parameters to SO2 was monitored during and after fumigation. The following results were obtained: (1) Inhibition of COa assimilation in the light was accompanied by increased reduction of the quinone acceptor, QA, of photosystem II and by increased oxidation of the electrondonor pigment PToo of photosystem I. Increased control of photosystem II activity in the SO2-inhibited state was also indicated by increased light scattering and by increased non-photochemical quenching of chlorophyll fluorescence. Both are indicators of chloroplast energization. Apparently, SO2 did not decrease but rather increased energization of the chloroplast thylakoid system by light. (2) Accumulation of dihydroxyacetone phosphate, fructose-l,6-phosphate and ribulose-l,5-phosphate and a decrease of 3-phosphoglycerate and hexosephosphate indicated that SO2 inhibited enzymes of the Calvin cycle. (3) Stimulated postillumination CO2 evolution suggested that when photosynthesis declined respiration increased to provide energy for repair reactions. (4) Increased leaf absorbance at 505 nm indicated increased stimulation of zeaxanthin formation in thylakoid membranes under the influence of SO2. A similar increase in 505-nm absorbance could be induced by high Dedicated to Professor O.L. Lange on the occasion of his 65th birthday * On leave from the Centre for Multidisciplinary Sciences, University of Belgrade, Yugoslavia Abbreviations: Chl = chlorophyll; DHAP = dihydroxyacetone phosphate; FBP=fructose-l,6-bisphosphate; F6P=fructoce-6-phosphate; F, Fm, Fm', Fo, Fo'=ch!orophyll fluorescence levels; PGA = 3-phosphoglycerate; P7oo = primary donor of photosystem I; QA = primary quinone acceptor of photosystem II; qp = photochemical quenching of chlorophyll fluorescence; NPQ = non-photochemical quenching of chlorophyll fluorescence; RuBP=ribulose-1,5-bisphosphate Correspondence to: U. Heber concentrations of CO2. In darkened leaves, SO 2 did not produce changes in 505-nm absorbance. (5) While zeaxanthin formation was stimulated, changes in the fluorescence of the pH-indicating dye pyranine, which had been fed to the leaves, indicated acidification of the cytoplasm of leaf cells by SO 2. Maximum acid production by SO 2 required light. In contrast, cytoplasmic acidification of leaf cells by CO2 was similar in the light and in the dark. (6) Since zeaxanthin formation is known to depend on the acidification of the thylakoid lumen, SO2-dependent zeaxanthin formation indicated SO2-dependent acidification of the thylakoid lumen as the indirect result of cytoplasmic acidification by SO2. (7) Inhibition of photosynthesis and other effects of SO2 were fully reversible in the light. Detoxification of SO2 and reactivation of the photosynthetic apparatus were slow or absent in the dark. Light had a dua...

Chloroplast pH values and buffer capacities in darkened leaves as revealed by CO2 solubilization in vivo

“…Protons appear in or disappear from different cell compartments as a result of metabolic processes which either generate or consume acid and base. Cells exposed to air pollutants such as SO 2 may suffer appreciable acidification because this gas, Abbreviation: Chl = chlorophyll Correspondence to: M.Hauser; Fax: 49(931)71446; E-mail: mattes @vax.rz.uni-wuerzburg.de when dissolved in aqueous cellular compartments, reacts with water to form sulfurous acid which may be oxidized to sulfuric acid (Laisk et al 1988a,b;Veljovic-Jovanovic et al 1993).…”

From horse thief to professor: confessions of a plant physiologist

“…It confirmed conclusions from research work performed about 100 years earlier at Tharandt, next to the village of my childhood, when trees had died in Saxony as industrialization had dramatically increased the burning of sulphur-containing coal. A postdoc, Sonja Veljovic-Iovanovic, doing good work on SO 2 (Veljovic-Jovanovic et al 1993), did not make my life easier when I protected her, a proud Serbian national, in her private war against German public opinion during the Balkan conflict. Work on forest damage was extended to include ozone which is formed in bright sunshine from a reaction between nitrogen oxide and oxygen (Luwe and Heber 1995).…”

Control of Photosystem II in spinach leaves by continuous light and by light pulses given in the dark

“…Zeaxanthin absorbs more strongly at 505 nm than violaxanthin. This has been used repeatedly to measure zeaxanthin formation in the light (Bilger et al 1989;Bj6rkman 1990, 1994;Ruban et al 1991;Veljovic-Jovanovic et al 1993). Dithiothreitol (DTT), which is known to inhibit formation of zeaxanthin from violaxanthin (Yamamoto and Kamite 1972;Demmig-Adams et al 1990;Bj6rkman 1990, 1994), when fed to a leaf through the petiole, largely abolished the slow absorption increase seen in the presence of 20% CO2 and the slow decline observed when CO2 was subsequently removed• Only fast absorbance changes were similar in a DTT-fed leaf (data not shown) and in the experiment shown in Figure 4.…”