Jociel Nascimento de Noronha¹, Tadeu dos Reis de Oliveira¹, Mateus Santana Rodrigues¹, Renan Carrari Santos¹, Vanildo Silveira¹, Claudete Santa Catarina¹

Iron (Fe²⁺) is an essential micronutrient for plants, participating in various physiological and metabolic processes, including chlorophyll biosynthesis, respiration, redox reactions, and electron transport during photosynthesis. However, excessive iron accumulation can be toxic, primarily due to the overproduction of reactive oxygen species (ROS). Mining activities have become one of the main sources of potentially toxic elements in the environment, including iron. The years 2015 and 2019 were marked by two of the most severe environmental disasters in Brazilian history: the collapses of the Fundão and Córrego do Feijão dams, respectively. In this context, the use of plant species with phytoremediation potential in iron-contaminated areas has gained attention as a strategy to mitigate environmental impacts. Among these species, Albizia lebbeck is a fast-growing pioneer tree considered a promising candidate for the recovery of metal-contaminated environments. This study aimed to evaluate the effects of different concentrations of iron(II) sulfate on seed germination and seedling development of A. lebbeck, focusing on changes in the proteomic profile, endogenous plant hormone levels, photosynthetic pigments, and polyamines. Seeds were germinated in increasing concentrations (0, 2, 4, 8, 16, 24, and 32 mM) of iron(II) sulfate (FeSO₄ . 7H₂O). After 12 days of incubation, fresh weight (FW) and dry weight (DW) were measured, and samples were collected for proteomic, hormonal, pigment, and polyamine analyses. Higher concentrations (16, 24, and 32 mM) of iron(II) sulfate negatively affected seed germination and seedling growth. A total of 368 proteins were identified. The comparison between 4 and 0 mM treatments revealed similar proteomic profiles, suggesting that 4 mM did not induce phytotoxic effects. However, at 24 mM, there was a reduction in proteins such as malate dehydrogenase (involved in the Krebs cycle), oxygen-evolving enhancer proteins, and chlorophyll a/b binding proteins of the light-harvesting complex, indicating possible impairment of the photosynthetic apparatus. Additionally, reductions were observed in chlorophyll and carotenoid contents, as well as in the levels of indole-3-acetic acid (IAA), abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA), while the level of 1-aminocyclopropane-1-carboxylic acid (ACC) increased in seedlings exposed to 24 mM Fe²⁺. Furthermore, the endogenous content of putrescine (Put) was lower at 4 mM compared to 24 mM, whereas the levels of spermine (Spm) and total polyamines were higher at 24 mM. The results highlight A. lebbeck as a promising candidate for phytoremediation programs in iron-contaminated areas caused by mining activities, contributing to the environmental recovery of degraded ecosystems. Although phytotoxic effects were observed at high Fe²⁺ concentrations, the species demonstrated tolerance up to 8 mM.

Agradecimentos: CAPES, CNPq, FAPERJ, UENF, PGPV