Coordination of physiological and morphological acclimation of shade-grown tree saplings to late-season canopy gap formation
Naidu, Shawna Lynn
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https://hdl.handle.net/2142/22945
Description
Title
Coordination of physiological and morphological acclimation of shade-grown tree saplings to late-season canopy gap formation
Author(s)
Naidu, Shawna Lynn
Issue Date
1996
Doctoral Committee Chair(s)
DeLucia, Evan H.
Department of Study
Biology, Botany
Plant Biology
Discipline
Plant Biology
Biology, Plant Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Botany
Biology, Ecology
Agriculture, Forestry and Wildlife
Biology, Plant Physiology
Language
eng
Abstract
The purpose of my research was to test the hypothesis that if shade-grown deciduous hardwood saplings respond positively to late-season canopy gaps, then morphological and physiological changes at both the organ and whole-plant level will result in greater carbon gain of saplings exposed to gaps relative to saplings remaining in the shade; that is, shade-developed saplings will acclimate to late-season canopy gaps. Late-season canopy gap formation was simulated by growing potted saplings in the forest understory and moving them to a naturally occurring canopy gap after leaf development was completed in the shade. A series of experiments with the same basic experimental design was conducted on up to four species of temperate deciduous hardwoods: red oak (Quercus rubra L.), sugar maple (Acer saccharum Marsh.), tulip poplar (Liriodendron tulipifera L.), and white ash (Fraxinus americana L.). Physiological acclimation responses included higher photosynthetic rates in shade-developed foliage upon exposure to higher irradiance and temperature conditions within the gap for each species. However, the magnitude of this change and associated physiological responses varied among species. In general, the increase in photosynthetic rate was correlated with increased stomatal conductance and leaf nitrogen content and, for red oak, decreased susceptibility to photoinhibition. Morphological acclimation responses also varied among species, and included greater allocation to new leaf production and root production after exposure to a gap. Species such as red oak, which acclimated to canopy gaps (increased carbon gain within the season of gap formation), demonstrated coordinated changes in both physiological and morphological mechanisms of acclimation. Conversely, sugar maple had a much more limited acclimation response, reflected in a greater susceptibility to photoinhibition and stomatal limitations to photosynthesis of shade-developed foliage, and limited production of new leaves within the gap. Interspecific comparisons suggest that acclimation involves a suite of coordinated processes rather than trade-offs between mutually exclusive mechanisms of acclimation.
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