Journal of Experimental Botany, Vol 49, 213-219, Copyright © 1998 by Oxford University Press
G Lorenc-Plucinska
Sulphite at concentrations from 0.05 to 5.0 mM was supplied to illuminated,
detached poplar (Populus deltoides Bart. ex Marsh)
leaves via the transpiration stream. The rate of CO2 fixation and
partitioning of newly fixed carbon between sucrose and starch were measured
and compared with the contents of selected phosphorylated intermediates,
the contents of fructose-2,6-bisphosphate (Fru2,6BP) and the activation of
sucrose-phosphate synthase (SPS). Supplying leaves with
ARTICLES
The effect of sulphite on the regulation of photosynthetic sucrose synthesis in poplar leaves
Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, PL-62-035 Kornik, Poland. E-mail: idkornik@rose.man.poznan.pl
0.5 mM sulphite led to an increase in the
sucrose/starch partitioning ratio without altering the rate of
14CO2 fixation. The increase in sucrose synthesis
compared to starch synthesis was accompanied by relatively small changes of
3-phosphoglyceric acid (PGA), fructose-1,6-bisphosphate (Fru1,6BP), hexose
phosphates (hexose-)), uridine 5'-diphosphoglucose (UDPGlc), an
accumulation of triose phosphates (triose-P), an activation of SPS, and
decreased Fru2,6BP contents. Supplying leaves with
1.0 mM sulphite
decreased 14CO2 assimilation and increased
partitioning of fixed carbon into starch. A selective inhibition of sucrose
synthesis was accompanied by an accumulation of triose-P, Fru1,6BP,
hexose-P, and a decrease of PGA contents. There was also a large increase
of Fru2,6BP contents and a decline in the activation of SPS. It could be
argued that sulphite affects the allocation of photosynthetic carbon to
sucrose and that sulphite can inhibit photosynthesis via a selective
inhibition of sucrose synthesis.Key words:
Fructose-2,6-bisphosphate, metabolites, Populus
deltoides, sucrose-phosphate synthase, sucrose synthesis,
sulphite stress.
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