a1 Department of Plant Ecology, University of Utrecht, Lange Nieuwslraat 106, 3512 PN Utrecht, The Netherlands
a2 Laboratorio de Ecología, Facultad de Ciencias, Universidad National Autónoma de México, 04510 México DF, México
A comparison is made of the light acclimation potential of seedlings of three canopy species of the tropical rain forest of Los Tuxtlas, Mexico: Cordia megalantha, Lonchocarpus guatemalensis, and Omphalea oleifera. These species showed similar growth rates in a range of microhabitats. Gap dynamics were simulated by transferring plants between three environments: beneath a closed canopy, a small gap, and a large gap. Plants of all three species were able to adjust their morphology and growth rates in response to changes in light availability. Growth rates increased when plants were moved to a (larger) gap, and decreased when plants were moved to a more shaded environment. Shade-grown plants were able to acclimate faster to increasing light availability than sun-grown plants to decreasing light availability. Also, plants moved from shady to sunny conditions showed higher relative growth rates than sun control plants, whereas sun-grown plants when moved to the shade showed lower relative growth rates than shade control plants. Species differed in their response to gap dynamics. Omphalea could not acclimate morphologically to shading, but reacted faster than the other species in response to the occurrence of a large gap. Acclimation potential seemed to be related to plasticity in physiological rather than in morphological traits. Suppressed seedlings of all three species performed well in the shade, and were able to acclimate rapidly to gap-conditions.
(Accepted July 24 1990)
c1 Correspondence should be sent to J. Popma, Nijmegen.
p1 Present address: Computing Centre, University of Nijmegen, Geert Grooteplein Z 41, 6525 GA Nijmegen, The Netherlands
p2 Present address: Department of Forestry, Agricultural University, PO Box 342, 6700 AH Wageningen, The Netherlands