The alternative respiratory pathway allows sink to cope with changes in carbon availability in the sink-limited plant Erythronium americanum
Résumé
Mechanisms that allow plants to cope with a recurrent surplus of carbon in conditions of imbalance between source and sink activity has not received much attention. The response of sink growth and metabolism to the modulation of source activity was investigated using elevated CO2 and elevated O3 growth conditions in Erythronium americanum. Sink activity was monitored via slice and mitochondrial respiratory rates, sucrose hydrolysis activity, carbohydrates, and biomass accumulation throughout the growth season, while source activity was monitored via gas exchanges, rubisco and phosphoenolpyruvate carboxylase activities, carbohydrates, and respiratory rates. Elevated CO2 increased the net photosynthetic rate by increasing substrate availability for rubisco. Elevated O3 decreased the net photosynthetic rate mainly through a reduction in rubisco activity. Despite this modulation of the source activity, neither plant growth nor starch accumulation were affected by the treatments. Sucrose synthase activity was higher in the sink under elevated CO2 and lower under elevated O3, thereby modulating the pool of glycolytic intermediates. The alternative respiratory pathway was similarly modulated in the sink, as seen with both the activity and capacity of the pathway, as well as with the alternative oxidase abundance. In this sink-limited species, the alternative respiratory pathway appears to balance carbon availability with sink capacity, thereby avoiding early feedbackinhibition of photosynthesis in conditions of excess carbon availability.
Mots clés
alternative pathway
carbohydrate
carbon allocation
carbon metabolism
erythronium americanum
respiration
sink limitation
enzyme activity
growth
hydrolysis
metabolism
oxygen
photosynthesis
ribulose-bisphosphate carboxylase
ribulose-1,5-diphosphate carboxylase
ribulose-1,5-diphosphate oxygenase
source sink relations
starch
monocotyledons
Domaines
Botanique
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