Photosynthetic acclimation of the liana Stigmaphyllon lindenianum to light changes in a tropical dry forest canopy |
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Authors: | Gerardo Avalos Stephen S Mulkey |
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Institution: | (1) Department of Biology, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121-4499, USA e-mail: gavalos@cariari.ucr.ac.cr, Fax: +1-314-5166233, US;(2) Department of Botany, University of Florida, P.O. Box 118526, Gainesville, FL 32611-8526, USA, US |
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Abstract: | Tropical plant canopies show abrupt changes in light conditions across small differences in spatial and temporal scales.
Given the canopy light heterogeneity, plants in this stratum should express a high degree of plasticity, both in space (allocation
to plant modules as a function of opportunity for resource access) and time (photosynthetic adjustment to temporal changes
in the local environment). Using a construction crane for canopy access, we studied light acclimation of the liana Stigmaphyllon lindenianum to sun and shade environments in a tropical dry forest in Panama during the wet season. Measured branches were randomly distributed
in one of four light sequences: high- to low-light branches started the experiment under sun and were transferred to shade
during the second part of the experiment; low- to high-light branches (LH) were exposed to the opposite sequence of light
treatments; and high-light and low-light controls , which were exposed only to sun and shade environments, respectively, throughout
the experiment. Shade branches were set inside enclosures wrapped in 63% greenhouse shade cloth. After 2 months, we transferred
experimental branches to opposite light conditions by relocating the enclosures. Leaf mortality was considerably higher under
shade, both before and after the transfer. LH branches reversed the pattern of mortality by increasing new leaf production
after the transfer. Rates of photosynthesis at light saturation, light compensation points, and dark respiration rates of
transferred branches matched those of controls for the new light treatment, indicating rapid photochemical acclimation. The
post-expansion acclimation of sun and shade foliage occurred with little modification of leaf structure. High photosynthetic
plasticity was reflected in an almost immediate ability to respond to significant changes in light. This response did not
depend on the initial light environment, but was determined by exposure to new light conditions. Stigmaphyllon responded rapidly to light changes through the functional adjustment of already expanded foliage and an increase in leaf
production in places with high opportunity for carbon gain.
Received: 24 April 1998 / Accepted: 11 May 1999 |
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Keywords: | Light acclimation Canopy ecology Lianas Phenotypic plasticity Tropical dry forest |
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