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The inhibition of photosynthesis and photorespiration in isolated mesophyll cells of Phaseolus and Lycopersicon by reduced osmotic potentials
Author(s) -
Mawson Bruce T.,
Colman Brian
Publication year - 1983
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1983.tb00724.x
Subject(s) - photorespiration , photosynthesis , phaseolus , lycopersicon , sorbitol , osmotic pressure , biophysics , botany , osmotic shock , biology , incubation , chemistry , biochemistry , gene
Mesophyll cells isolated from Phaseolus vulgaris and Lycopersicon esculentum show decreasing photosynthetic rates when suspended in media containing increasing concentrations of osmoticum. The photosynthetic activity was sensitive to small changes in osmotic potential over a range of sorbitol concentrations from 0.44 M (−1.08 MPa) to 0.77 M (−1.88 MPa). Photorespiration assayed by 14 CO 2 release in CO 2 ‐free air and by 14 CO 2 release from the oxidation of [1– 14 C] glycolate also decreased as the osmotic potential of the incubation medium was reduced. The CO 2 compensation points of the cells increased with increasing concentration of osmoticum from approximately 60 μ I −1 1 at −1.08 MPa to 130 μl 1 −1 for cells stressed at −1.88 MPa. Changes in photosynthetic and photorespiratory activities occurred at moderate osmotic potentials in these cells suggesting that in whole leaves during a reduction in water potential, non‐ stomatal inhibition of CO 2 assimilation and glycolate pathway metabolism occurs simultaneously with stomatal closure.