Plant Spinescence: Architectural Modularity and Functional Plurality

Spiny plant structures, commonly interpreted as defensive devices against herbivory, exhibit a morphological and positional diversity suggesting multiple origins and functions. Their ontogenetic and architectural distribution indicates that their previously proposed defensive effectiveness remains debatable. Morphological and ecological observations suggest that these structures may perform multiple roles, including leaf lamina stiffening, capture of organic matter and water, microclimatic regulation, water coalescence and drainage, spatial colonization for improved access to light, and modulation of abiotic constraints. In this context, spines may be integrated into a broader set of ecological functions that mitigate the growth–defense allocation trade-off. This article does not aim to experimentally demonstrate a single function for spiny structures, but rather to propose—based on diverse morphological and ecological examples—an expanded interpretative framework that may guide future functional investigations.