Morfobiometria e alometria de frutos e sementes de Solanum americanum Mill. (Solanaceae)

Abstract

This study investigated the morphometric characteristics and allometry of fruits and seeds of Solanum americanum Mill. (commonly known as black nightshade), a species with a wide global distribution. The research was conducted by collecting fruits from mother plants located in fragments of the Atlantic Forest and in urban areas of João Pessoa, Paraíba. The main objective was to describe the morphometric measurements of fruits and seeds, with the specific aims of measuring their dimensions, fresh mass, and establishing the allometric relationships between the variables. The three spatial axes of the fruits (width, height, and thickness), fresh mass, pericarp mass, number of seeds per fruit, seed area, water content, and thousand-seed weight were analyzed. The results showed that the fruits are globular berries with average dimensions of 6.80 mm (X-axis), 6.30 mm (Y-axis), and 7.30 mm (Z-axis), with an average fresh mass of 0.24 g and containing, on average, 53 seeds each. Principal Component Analysis (PCA) explained 85.5% of the data variability, revealing a strong positive correlation between fruit dimensions (r between 0.85 and 0.93). A moderate correlation was observed between fruit size and the number of seeds (r between 0.42 and 0.51), and a weak correlation between the number of seeds and their area (r = -0.13). The low water content of the seeds (12.25%) classifies them as orthodox, indicating tolerance to desiccation. It is concluded that S. americanum exhibits high phenotypic plasticity, with a reproductive strategy that combines the production of a large number of viable seeds (a ruderal characteristic) with a significant investment in a fleshy pericarp, suggesting effective zoochorous dispersal. These results contribute to the understanding of the autoecology and establishment strategies of this species in disturbed environments.