Tropical rainforest trees adjust leaf traits during ontogeny to cope with changes in the physical environment and maximize their carbon uptake. The aim of this study was to determine the plasticity index (PI) of leaf traits in understory and canopy leaves of six Amazonian tree species. In four of the six species the PI of leaf traits varied within species, and in four of the ten leaf traits assessed, the PI differed between species. The greatest PI values were found for stomatal density (Ds) and CO2-saturated photosynthesis, and the lowest ones were found for stomatal size, and leaf thickness. Despite the differences in PI values within species, the mean PI was similar in all the six species. As the saplings grow toward the canopy, the strategy to increase carbon uptake involves increasing Ds and leaf nitrogen and reducing stomatal size., R. A. Marenco, M. A. B. Camargo, S. A. Antezana-Vera, M. F. Oliveira., and Obsahuje seznam literatury
The aim of this work was to assess the effect of leaf thickness, leaf succulence (LS), specific leaf area (SLA), specific leaf mass (Ws) and leaf water content (LWC) on chlorophyll (Chl) meter values in six Amazonian tree species (Carapa guianensis, Ceiba pentandra, Cynometra spruceana, Pithecolobium inaequale, Scleronema micranthum and Swietenia macrophylla). We also tested the accuracy of a general calibration equation to convert Minolta Chl meter (SPAD-502) readings into absolute Chl content. On average, SPAD values (x) increased with fresh leaf thickness (FLT [μm] = 153.9 + 0.98 x, r2 = 0.06**), dry leaf thickness (DLT [μm] = 49.50 + 1.28 x, r2 = 0.16**), specific leaf mass (Ws [g (DM) m-2] = 6.73 + 1.31 x, r2 = 0.43**), and leaf succulence (LS [g(FM)] m-2 = 94.2 + 1.58 x, r2 = 0.19**). However, a negative relationship was found between SPAD values and either specific leaf area [SLA (m2 kg-1) = 35.1 - 0.37 x, r 2 = 0.38**] or the leaf water content (LWC [%]= 80.0- 0.42 x, r2 = 0.58**). Leaf Chl contents predicted by the general calibration equation significantly differed (p<0.01) from those estimated by species-specific calibration equations. We conclude that to improve the accuracy of the SPAD-502 leaf thickness and LWC should be taken into account when calibration equations are to be obtained to convert SPAD values into absolute Chl content. and R. A. Marenco, S. A. Antezana-Vera, H. C. S. Nascimento.