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JXB Advance Access originally published online on August 26, 2009
Journal of Experimental Botany 2009 60(15):4235-4248; doi:10.1093/jxb/erp255
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© 2009 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

The alternative respiratory pathway allows sink to cope with changes in carbon availability in the sink-limited plant Erythronium americanum

Anthony Gandin1,2,*, Line Lapointe1 and Pierre Dizengremel2

1Département de biologie et Centre d'étude de la forêt, Université Laval, Québec (QC), Canada G1V 0A6
2Faculté des Sciences et Techniques, UMR 1137 Écologie et écophysiologie forestières, Nancy-Université, BP 239, 54506 Vandoeuvre, France

* To whom correspondence should be addressed: E-mail: anthony.gandin.1{at}ulaval.ca

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 feedback-inhibition of photosynthesis in conditions of excess carbon availability.

Key words: Alternative pathway, bulbous plant, carbohydrate, carbon allocation, carbon metabolism, Erythronium americanum, respiration, sink limitation

Received 28 April 2009; Revised 14 July 2009 Accepted 5 August 2009


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