Deciduous forest spring ephemerals are characterized by a short epigeous growth season, starting to snow melt and ending with canopy closure. In constant light conditions, plants still senesce after 35-40 days of growth. To explain this constrained senescence, Lapointe (2001, Physiol. Plant. 113:151-157) suggests that the initiation of leaf senescence could be influence by carbohydrate sink demand rather than abiotic factors. The aim of this study is to clarify the role of the sink on phenology, carbon allocation and and growth of Erythronium americanum, one of the most commun spring ephemerals in north-american mapple forest. Due to its simple morphology (1 leaf vs 1 bulb), Erythronium americanum is an interesting biological model to study whole plant C partionning, which is very close to a theoretical source-sink model. Many different analysis are carried out, from whole plant to the cell. First results showed that a lower growth temperature (8/6°C), modulating sink activity, induce a larger perennial organ than higher temperature (12/8°C, 18/14°C); a unique case amongst temperate species. Hexose/sucrose ratio could control cell development in bulb, regulating thus starch storage capacity. Maximum capacity of the sink being quickly reached at high temperatures, there is a precocious foliar senescence. But, signal, which link carbon demand of sink and initiation of foliar senescence, remains unknown. On the other hand, a modulation of source activity, stimulated by high CO2 concentration or inhibited by ozone fumigation, have no effect on carbohydrate accumulation. Mitochondrial respiration in bulb seems closely correlated to net assimilation rate in the leaf, especially the alternative pathway (AOX). This modulation of the alternative respiration could allow to burn the surplus of carbon translocated to adapt the size of hexose pool available to storage capacity, illustrating a sink limited model.
- PhD, Biology, en préparation (Université Laval, Québec, Canada and Université Henri Poincaré Nancy I, France)
- M.Sc., Forest Biology, 2006 (Université Henri Poincaré, Nancy, France)
- Maîtrise, Cellular Biology and Plant Physiology, 2004 (Université François Rabelais, Tours, France)
- B.A., Biology, 2003 (Université François Rabelais Tours, France)
Gandin, A., Dizengremel, P. and Lapointe, L. Poster: "Alternative respiratory pathway : A way to reduce imbalance between source and sink activity". Plant Canada 2007, Saskatoon (SK), 10-14 juin 2007.
Gutjahr, S., Gandin, A. and Lapointe, L. Poster: "Is leaf longevity of perennial spring ephemerals controlled by the growth of their belowground organ ? The case of Erythronium americanum". Plant Biology 2006, Boston (MA), 5-9 août 2006.