The effect of sun and shade on the leaves of four coastal tree species.

Abstract

Mimusops caffra, Euclea netetensis, Olea woodiana and Peddiea africana are tree species associated with different successional stages in a coastal dune forest. Saplings of these tree species were established in four different light intensities. These were full sun, 40% shade, 70% shade and 90% shade. The hypothesis proposed that the species from different successional stages are preadapted for a particular light environment and are disadvantaged in other light environments. Growth, morphological, biochemical and physiological aspects of the four species in the four light environments were determined. Growth rates showed no consistent pattern with respect to light intensity. However, most species, irrespective of their successional status, had the best growth response in either 40% or 70% shade treatments. All the species showed typical sun and shade responses for morphological, anatomical and some biochemical characteristics. Photosynthetic responses were complex and showed no relationship between the successional status of the species and the light conditions in which they were grown. There appears to be very little relationship between the growth responses, the measured biochemical and morphological aspects, assimilation rates and the successional status of the species. Light intensity is therefore not the sole driving force of forest succession but one of the many factors that contribute to the overall process.