title: Age- and size-related trends in woody plant shoot development: regulatory pathways and evidence for genetic control.
abstract: Woody plants exhibit significant and predictable patterns of change in morphology and physiology as they become older and larger. Four models of potential pathways controlling these changes are presented: a stimulus-response model in which fully developed organs respond to changes in environment (defined here as everything external to the organ); an extrinsic model in which the attributes of developing organs are determined by environmental factors; an intrinsic model in which changes are a result of programmed changes in gene expression; and an extrinsic-intrinsic model in which changes in gene expression are induced by environmental factors. We review evidence that a genetic component is involved in controlling age- and size-related changes in foliar morphology and physiology and discuss the possibility of complex interactions among model pathways.
authors.affiliation: Department of Forest Ecosystem Science, University of Maine, Orono, Maine 04469-5755, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Day
authors.forename: M S
authors.initials: MS
authors.lastname: Greenwood
authors.forename: C
authors.initials: C
authors.lastname: Diaz-Sala
mesh_terms: D008954:Models, Biological; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development*; D014197:Trees / Q000235:genetics / Q000254:growth & development*