Leaf Characteristics of the Tropical Rain Forest Flora of Los Tuxtlas, Mexico

Abstract

Sun leaves of 68 species of trees, shrubs, and palms of the tropical rain forest of Los Tuxtlas, Veracruz, Mexico, were studied with respect to morphology, anatomy, and mineral levels. The average leaf had a size of 0.95 dm2 and an oblongate form (three times as long as wide); per m2 surface area it contained 79 g of dry matter, a maximum of 170 g water, and 13.0, 1.0, and 7.7 mg of N, P, and K, respectively. The average leaf had an abaxial stomatal density of 409 mm-2, and stomata were 21 μm long. Leaf thickness was 207 μm, and nonpalisade mesophyll was 1.4 times as thick as palisade mesophyll. Many species (75%) had a multilayered palisade mesophyll, whereas the frequency of occurrence of trichomes (5%) and of crystals in the lamina (15%) was low. Variation among species was moderately high, nearly all parameters had a coefficient of variation (CV) between 28% and 57%. Leaf area, leaf shape, and stomatal density had a CV of over 100% due to a skewed distribution. Several parameters were correlated, especially specific leaf weight (SLW) and lamina thickness. Los Tuxtlas leaves were compared with leaves from other tropical rain forests. In general, the leaves of Los Tuxtlas had a similar leaf size, a relatively low SLW, a high N and P content, low N/P and K/P ratios, a high stomatal density, a thin lamina, and a low nonpalisade to palisade ratio. With respect to leaf characteristics, the Los Tuxtlas forest may be regarded as a typical example of tropical lowland rain forest.