Strategies for protecting aboveground buds: role of secretory structures and morphoanatomical adaptations.

Abstract

The Brazilian Cerrado stands as the most biodiverse neotropical savanna, supporting a vast array of endemic species uniquely adapted to its challenging environment. These species have evolved under strong selective pressures imposed by recurrent natural disturbances, including pronounced seasonal drought, intense herbivory, and frequent fire events. Consequently, Cerrado species have evolved diverse morpho-anatomical adaptations to persist in this fire-prone ecosystem. Resprouting capacity -whether from belowground or aboveground buds-represents a key functional trait for post-disturbance regeneration. While thick bark has long been recognized as the primary mechanism protecting aerial meristematic tissues, emerging research reveals finer-scale adaptations that complement bark defenses. This study investigates the protective features of aerial buds in two herbaceous Chamaecrista species (Fabaceae) to the Brazilian Cerrado. We employed a multi-technique anatomical approach combining light microscopy, histochemical analysis, fluorescence microscopy, and scanning electron microscopy (SEM). Our results revealed the presence of secretory structures, such as colleters and extrafloral nectaries, which develop at distinct temporal stages, indicating different phases of bud protection throughout plant development. Additionally, structures such as hairy leaf primordia with phenolic compound accumulation, stipules, and accessory buds were observed, reinforcing both structural and chemical investments in the protection of aerial buds. These structures confer high resilience to intense UV radiation and herbivory, providing the species with greater resistance and the ability to withstand various environmental disturbances. These findings demonstrate that herbaceous Cerrado species employ sophisticated, multi-layered strategies for aerial bud protection, comparable in complexity to woody species. The discovery of such refined adaptive mechanisms in herbaceous and subshrub growth forms challenges the traditional woody-centered paradigm of Cerrado resilience research.