title: Growth and posture control strategies in Fagus sylvatica and Acer pseudoplatanus saplings in response to canopy disturbance.
abstract: OBJECTIVE
  Forest tree saplings that grow in the understorey undergo frequent changes in their light environment to which they must adapt to ensure their survival and growth. Crown architecture, which plays a critical role in light capture and mechanical stability, is a major component of sapling adaptation to canopy disturbance. Shade-adapted saplings typically have plagiotropic stems and branches. After canopy opening, they need to develop more erect shoots in order to exploit the new light conditions. The objective of this study was to test whether changes in sapling stem inclination occur after canopy opening, and to analyse the morphological changes associated with stem reorientation.
  
  
  METHODS
  A 4-year canopy-opening field experiment with naturally regenerated Fagus sylvatica and Acer pseudoplatanus saplings was conducted. The appearance of new stem axes, stem basal diameter and inclination along the stem were recorded every year after canopy opening.
  
  
  RESULTS
  Both species showed considerable stem reorientation resulting primarily from uprighting (more erect) shoot movements in Fagus, and from uprighting movements, shoot elongation and formation of relay shoots in Acer. In both species, the magnitude of shoot uprighting movements was primarily related to initial stem inclination. Both the basal part and the apical part of the stem contributed to uprighting movements. Stem movements did not appear to be limited by stem size or by stem growth.
  
  
  CONCLUSIONS
  Stem uprighting movements in shade-adapted Fagus and Acer saplings following canopy disturbance were considerable and rapid, suggesting that stem reorientation processes play a significant role in the growth strategy of the species.
authors: INRA, UMR1092, Laboratoire d'Etude des Ressources Foret Bois, Centre INRA de Nancy, Champenoux, France. collet@nancy.inra.fr
authors: Catherine
authors: C
authors: Collet
authors: Mériem
authors: M
authors: Fournier
authors: François
authors: F
authors: Ningre
authors: Ablo Paul-Igor
authors: AP
authors: Hounzandji
authors: Thiéry
authors: T
authors: Constant
mesh_terms: D031002:Acer / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects*; D000222:Adaptation, Physiological / Q000502:physiology*; D029964:Fagus / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects*; D005602:France; D018522:Gravitropism / Q000502:physiology; D008027:Light; D008954:Models, Biological; D018515:Plant Leaves / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D018520:Plant Shoots / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D014197:Trees / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects