LEAF ADAPTATIONS OF SOME SHOREA SPECIES TO SUN AND SHADE

Seedlings of four species of the genus Shorea section Doona were examined. All co-exist in the moist evergreen rain forest of southwestern Sri Lanka. Experiments were designed to investigate some physiological and anatomical attributes of leaves under different light conditions. The attributes considered were net photosynthesis, transpiration, stomatal conductivity, blade and cuticle thickness, stomatal frequency, thickness of upper epidermis and palisade mesophyll, and number of palisade layers. Results demonstrate the close association between anatomical adaptation and efficiency in physiological processes. Results also elucidate some of the relationships between distribution patterns of species across the forest topography and their differences in light and drought tolerance. This indicates that an important period determining site specialization of a specie's occurs during regeneration establishment. These relationships are not as simple or as ecologically noticeable though as for those relationships documented in many previous studies between tree species of markedly different successional stages or taxonomy.