Flux of SO/sub 2/ into leaf cells and cellular acidification by SO/sub 2/

Journal Article · Tue Dec 01 04:00:00 EST 1987 · Plant Physiol.; (United States)

OSTI ID:5394240

Pfanz, H; Martinoia, E; Lange, O L; Heber, U

A comparison of fluxes of SO/sub 2/ from the atmosphere into leaves with fluxes across biomembranes revealed that, apart from the cuticle, the main barrier to SO/sub 2/ entry into leaves are the stomates. SO/sub 2/ fluxes into leaves can be calculated with an accuracy sufficient for many purposes on the assumption that the intracellular SO/sub 2/ concentration is zero. SO/sub 2/ entering green leaf cells is trapped in the cytoplasm. In the light, the products formed in its reaction with water are processed particularly in the chloroplasts. Flux of SO/sub 2/ to the acidic central vacuole of leaf cells is insignificant. Intracellular acidification of barley mesophyll protoplasts by SO/sub 2/ was measured by the uptake of /sup 14/C-labeled 5,5-dimethyl-oxazolidine-2,4-dione. The measured acidification was similar to the acidification calculated from known buffer capacities and the rate of SO/sub 2/ influx when the H/sup +//SO/sub 2/ ratio was assumed to be 2. A comparison of photosynthesis inhibition by SO/sub 2/ with calculated acidification revealed different mechanisms of inhibition at low and at high concentrations of SO/sub 2/. At very low concentrations, inhibition by SO/sub 2/ was even smaller than expected from calculated acidification. The data suggest that, if acidification cannot be compensated by pH-stabilizing cellular mechanisms, it is a main factor of SO/sub 2/ toxicity at low SO/sub 2/ levels. At high levels of SO/sub 2/, anion toxicity and/or radical formation during oxidation of SO/sub 2/ to sulfate may play a large role in inhibition.

• Research Organization: Univ. of Wuerzburg, Germany, F.R.
• OSTI ID: 5394240
• Journal Information: Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 85:4; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550501 -- Metabolism-- Tracer Techniques
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BARLEY
CARBON 14 COMPOUNDS
CELL CONSTITUENTS
CELL MEMBRANES
CEREALS
CHALCOGENIDES
CHEMICAL REACTIONS
CHLOROPLASTS
CYTOPLASM
FOLIAR UPTAKE
GRASS
INHIBITION
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEAVES
MEMBRANES
OPENINGS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANT CELLS
PLANTS
STOMATA
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES
SYNTHESIS
TOXICITY
TRACER TECHNIQUES
UPTAKE