Photosynthetic plasticity of young plants of Carpotroche brasiliensis (Raddi) A. Gray, Achariaceae

Key message We analyzed the shade tolerance of a tropical tree species based on the plasticity of 22 photosynthetic traits. Carpotroche brasiliensis leaves have characteristics of a shade-tolerant species, with low photosynthetic plasticity. Abstract The objective of this study was to evaluate the photosynthetic plasticity of young Carpotroche brasiliensis plants in response to different light environments. This tropical tree species has some shade-tolerant traits, such as large and fleshy fruits, seeds with a high water content, and the ability for natural regeneration in the forest understory. In this way, we tested the hypothesis that, at the leaf scale, young C. brasiliensis plants have photosynthetic characteristics of shade-tolerant species, with low photosynthetic plasticity when grown under different light environments. For this, seedlings were subjected to four light treatments (60, 35, 25, and 15% full sunlight, corresponding to about 20.9, 11.9, 9.1, and 5.4 mol photons m −2 day −1 , respectively) for 5 months. We evaluated the photosynthetic plasticity at the leaf scale through morphological and anatomical variables, as well as variables associated with the diffusive, photochemical, and biochemistry phases of photosynthesis. All key photosynthetic variables measured exhibited values of typical shaded leaves. The highest simplified relative distance plasticity index (RDPI) for light treatments was found for light compensation point (0.32), performance index (0.30), photochemical reflectance index (0.30), mesophyll conductance (0.27), dark respiration rate (0.27), and leaf area (0.19). The lowest RDPI for light treatments was found for the leaf anatomical variables (< 0.1). From the 22 photosynthesis-related variables analyzed, we conclude that, on a leaf scale, young C. brasiliensis plants exhibit characteristics of a typical shade-tolerant species. Based on our results, we can recommend the plantation of C. brasiliensis seedlings in forest enrichment programs or agroforestry systems, in which other tree species are present providing light environments below 35% full sunlight or about 10 mol photons m −2 day −1 .