title: Light acclimation strategies change from summer green to spring ephemeral as wild-leek plants age.
abstract: Spring-ephemeral forest-herbs emerge early to take advantage of the high-light conditions preceding canopy closure; they complete their life cycle in a few weeks, then senesce as the tree canopy closes. Summer greens acclimate their leaves to shade and thus manage to maintain a net carbon gain throughout summer. Differences in phenology among life stages within a species have been reported in tree saplings, whose leaf activity may extend beyond the period of shade conditions caused by mature trees. Similar phenological acclimation has seldom been studied in forest herbs.
  
  
  
  We compared wild-leek bulb growth and leaf phenology among plants from seedling to maturity and from under 4 to 60% natural light availability. We also compared leaf chlorophyll content and chl a/b ratio among seedlings and adult plants in a natural population as an indicator of photosynthetic capacity and acclimation to light environment.
  
  
  
  Overall, younger plants senesced later than mature ones. Increasing light availability delayed senescence in mature plants, while hastening seedling senescence. In natural populations, only seedlings acclimated to the natural reduction in light availability through time.
  
  
  
  Wild-leek seedlings exhibit a summer-green phenology, whereas mature plants behave as true spring ephemerals. Growth appears to be more source-limited in seedlings than in mature plants. This modulation of phenological strategy, if confirmed in other species, would require a review of the current classification of species as either spring ephemerals, summer greens, wintergreens, or evergreens.
authors.affiliation: Département de phytologie, Université Laval, Québec, Québec, Canada and Centre de recherche en innovation sur les végétaux, Québec, Québec, Canada pierre-paul.dion.1@ulaval.ca.
authors.forename: Pierre-Paul
authors.initials: PP
authors.lastname: Dion
authors.affiliation: Institut de recherche en biologie végétale, Université de Montréal, Montréal, Québec, Canada and Center for Forest Research, Québec, Canada.
authors.forename: Jacques
authors.initials: J
authors.lastname: Brisson
authors.affiliation: Institut de recherche en biologie végétale, Université de Montréal, Montréal, Québec, Canada and Center for Forest Research, Québec, Canada.
authors.forename: Bastien
authors.initials: B
authors.lastname: Fontaine
authors.affiliation: Département de biologie, Université Laval, Québec, Canada and Center for Forest Research, Québec, Canada.
authors.forename: Line
authors.initials: L
authors.lastname: Lapointe
mesh_terms: D000064:Acclimatization / Q000528:radiation effects*; D002734:Chlorophyll / Q000378:metabolism; D008027:Light; D016013:Likelihood Functions; D019697:Onions / Q000502:physiology* / Q000528:radiation effects*; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000033:anatomy & histology / Q000502:physiology / Q000528:radiation effects; D012621:Seasons
chemical_list: D002734:Chlorophyll
keywords: Allium tricoccum; juvenile character; leaf life-span; life history; light; phenology; photosynthetic rate; spring ephemeral; summer green; understory herb