Carbon nanoparticle effects on Bertholletia excelsa BONPL. growth and mophophysiology across planting systems

The Amazon, the planet's largest tropical forest, faces intense degradation, requiring restoration strategies with native species such as the use of Bertholletia excelsa in diversified planting systems and innovative technologies, such as the carbon nanoparticle arbolina, with possibilities to enhance growth and physiological processes. The objective of this study was to investigate growth, ecophysiological responses and leaf venation density in B. excelsa plants cultivated in different planting systems and under the effect of the arbolina nanoparticle. The experiment was conducted in a randomized block design, in a 2 × 3 factorial scheme, totaling six treatments with five blocks each. The first factor was arbolina application (presence and absence/control) and the second was the planting systems: pure (PP with B. excelsa), mixed (PM with B. excelsa and Inga edulis) and agroforestry (SAF with B. excelsa, I. edulis, Theobroma cacao and Musa paradisiaca). At 60 days after planting, the application of arbolina commenced, by monthly foliar spraying (0.5–1.0 mL L⁻¹). Biometry and growth, leaf morphometry (leaf area and specific leaf area – SLA), relative water content, leaf anatomy (stomatal density - Sd and venation density by areoles), gas exchange, water use efficiency and chloroplastic pigment contents were evaluated. Growth was influenced by the planting system, affecting number of leaves and leaf flushes, while arbolina acted in a system-dependent manner, enhancing diameter and leaf emission. PM and SAF showed better performance, with higher SLA, Sd and areole size, evidencing physiological plasticity. The use of arbolina resulted in increased photosynthesis, transpiration, stomatal conductance (gs) and pigment accumulation without compromising water efficiency. Integrated analyses highlighted relative growth rate of diameter, gs and SLA as key variables, and principal component analysis and standardized mean Score indicated that the SAF and arbolina combination provided the best integrated performance. In conclusion, growth, physiology and leaf venation density of B. excelsa were modulated by the planting system and arbolina enhancing photosynthesis and pigments, with leaves of greater areole size and SLA reflecting functional adaptation to the environment, evidencing the species' plasticity and its restorative potential.