Coordination of physiological and morphological acclimation of shade-grown tree saplings to late-season canopy gap formation

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Plant Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Naidu, Shawna Lynn

Contributors dc:contributor

• DeLucia, Evan H.

• Biology, Botany
• Biology, Ecology
• Agriculture, Forestry and Wildlife
• Biology, Plant Physiology

Statement dc:rights

• Copyright 1996 Naidu, Shawna Lynn

Language dc:language

eng

Identifier

9780591089301
AAI9702620
(UMI)AAI9702620

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/22945