Effect of long‐term H2S fumigation on photosynthesis in spinach. Correlation between CO2 fixation and chlorophyll a fluorescence

Abstract

Spinach plunts (Spinacia oleracea L. cv. Monosa) were exposed to air with and without 0.25 μl l‐1 H2S. Effects of H2S exposure for up to 18 days on photosynthesis, dark respiration and on chlorophyll a fluorescence were studied. Dark respiration was not affected by H2S fumigation. Photosynthetic CO2 fixation decreased linearly with time in both control and fumigated plants. The rate of decrease in CO2 fixation was faster in the fumigated plants; after 14 days of exposure the fumigated plants showed a decrease in CO2 fixation of 23%äs compared with the control plants. The H2S‐induced decrease in CO2 fixation was accompanied by a decrease in quenching of the chlorophyll fluorescence. The most characteristic change in chlorophyll fluorescence was a decreased difference between maximum and steady‐state fluorescence [(P‐T)/P), suggesting a reduced efficiency in the use of photochemical energy in photosynthesis. Differences in CO2 fixation were more pronounced whcn measured at high light intensity; the maximum rate of CO2 fixation at light saturation decreased significantly with time in the H2S‐exposed plants; after 14 days of H2S exposure a decrease of more than 70% was noted. The decrease in CO2 fixation could not be attributed to a decreased chlorophyll content; on the contrary, chlorophyll content even slightly increased during fumigation. The initial increase in CO2 fixation rate with increasing light intensity was also reduced by prolonged H2S fumigation, indicating an effect of H2S fumigation on photosynthetic electron transport. Finally, the phytotoxicity of H2S is discusscd in relation to the H2S‐induced changes in photosynthetic CO2 fixation and chlorophyll a fluorescence, and the effect of H2S on leaf development observed in earlier studies.

Analysis of theArabidopsis O-Acetylserine(thiol)lyase Gene Family Demonstrates Compartment-Specific Differences in the Regulation of Cysteine Synthesis

“…In rice (Oryza sativa) roots, sulfide-induced inhibition of respiration could directly be explained by a reaction of sulfide with the heme group of cytrochrome c oxidase (Allam and Hollis, 1972). By contrast, shoot respiration was not susceptible to exposure to elevated atmospheric H 2 S levels (Maas et al, 1988). Total carbon, nitrogen, and sulfur analyses (see Supplemental Figure 4 online) showed comparable amounts of total N and S in all oastl insertion lines, suggesting no significant reduction of nutrient uptake by the root.…”

Stress responsive gene regulation in relation to hydrogen sulfide in plants under abiotic stress

“…De Kok et al () have studied that on fumigation of spinach leaves, about 40% of H 2 S can be converted to GSH which was reduced no sooner than the fumigation was stopped. Interestingly, the photosynthetic fixation and photosynthetic electron transport chain were not effected on H 2 S exposure in spinach (Maas et al ). Several studies have stated the role of sulfhydration in H 2 S based signaling in plants (Yang et al , Aroca et al , Paul and Snyder ).…”

Atmospheric H2S: Impact on Plant Functioning

“…This indicated that sulfide was oxidized by chloroplasts, its oxidation being initiated by superoxide formed upon illumination at the reducing side of photosystem I (De Kok et al, 1983a). Nevertheless, reductions in photosynthesis are unlikely to be the primary basis of H 2 S toxicity, since generally in intact plants photosynthesis was only reduced after prolonged exposure to toxic H 2 S concentrations (Maas et al, 1987a, 1988; De Kok, 1989, 1990).…”