Stem base and root anatomy of four young legumes from the Cerrado: Implications for fire resilience

Fabaceae is one of the most representative families of the Cerrado, a South American biome characterized by fire and drought. The anatomy of the species present in this biome is intrinsically related to their survival after a fire event, and is essential for understanding their ecological adaptations. This study aimed to describe the anatomical structure of the stem base and root of four native legume tree species (Albizia niopoides, Erythrina crista-galli, Inga laurina, and Senegalia polyphylla) at 6 and 18 months of age. For this purpose, the seedlings were grown in a greenhouse and then the stem base and root were fixed and dehydrated. Some samples were cut with a sliding microtome, and others were sectioned with a rotary microtome. The presence of starch was verified using Lugol's iodine. All species showed secondary growth even at 6 months, with periderm formation and species-specific cork development. Differences between ages included thickening and/or lignification of the cork and variations in the cambial zone activity. Buds were observed at the stem base of A. niopoides and S. polyphylla, suggesting early development of resprouting capacity. Anatomical differences were also noted in the arrangement of fibers, vessel elements, and parenchyma rays between species. Starch was detected mainly in the secondary xylem, varying in quantity and distribution between species and ages. These traits are linked to resilience under environmental stresses such as fire and drought. The findings contribute to understanding the anatomical plasticity and adaptive strategies of juvenile legumes in fire-prone Cerrado ecosystems.