ISSN:
1432-2048
Keywords:
Chloroplast metabolites
;
Photosynthesis (osmotic stress)
;
Spinacia (photosynthesis and water stress)
;
Water stress
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The levels of stromal photosynthetic intermediates were measured in isolated intact spinach (Spinacia oleracea L.) chloroplasts exposed to reduced osmotic potentials. Stressed chloroplasts showed slower rates of metabolite accumulation upon illumination than controls. Relative to other metabolites sedoheptulose-1,7-bisphosphate (SBP) and fructose-1,6-bisphosphate (FBP) accumulated in the stroma in the stressed treatments. Under these conditions 3-phosphoglycerate (3-PGA) efflux to the medium was restricted. Chloroplasts previously incubated with [32P]KH2PO4 and [32P]dihydroxyacetone phosphate ([32P]DAP) in the dark were characterized by very high FBP and SBP levels prior to illumination. Metabolism of these pools upon illumination increased with increasing pH of the medium but was consistently inhibited in osmotically stressed chloroplasts. The responses of stromal FBP and SBP pools under hypertonic conditions are discussed in terms of both inhibited light activation of fructose-1,6-bisphosphatase (EC 3.1.3.11) and sedoheptulose-1,7-bisphosphatase (EC 3.1.3.37), and likely increases in stromal ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) active-site concentrations.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00392240
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