Samara Linhares Pereira¹, Laíse Trugilio Moreira Marinho¹, Yrexam Rodrigues de Souza Ribeiro¹, Jociel Nascimento de Noronha¹, Mateus Santana Rodrigues ¹, Gonçalo Apolinário de Souza Filho², Vanildo Silveira², Claudete Santa Catarina¹

Albizia lebbeck (L.) Benth, a tree species from the Fabaceae family with pharmacological and medicinal uses, lacks studies on ex vitro rooting of nodal shoots. Indole-3-butyric acid (IBA) and sewage sludge organic compost are promising alternatives. This study evaluated the effect of IBA and organic compost on the rooting of micropropagated shoots of A. lebbeck and their proteomic profile. Shoots cultured in vitro on Murashige and Skoog medium supplied with 1 µM benzyladenine (BA) were used as explants. The bases were immersed for 1 minute in different concentrations (0, 10, 50, 100, 250, and 500 μM) of IBA. The most responsive IBA concentration was then used, and the shoots were transferred to a forest substrate and vermiculite (1:1; v/v) with varying proportions (0, 25, 50, 75, and 100%) of organic compost. After 55 days, rooting percentage, number and length of roots, and shoot growth were evaluated. Triplicate samples (300 mg fresh matter) were collected for proteomic analysis. The concentration of 250 μM IBA resulted in the highest root induction percentage, number of roots, and plantlet growth. Greater root lengths were significant higher at 10 and 250 μM. The absence of IBA and the 500 μM treatment were the least effective treatments. The addition of 25% organic compost to the rooting substrate promoted the best results in rooting and plantlet growth, compared to its absence and higher concentrations (75 and 100%). The use of 25% organic compost stimulated the development of adventitious roots in A. lebbeck, increasing induction from 37 to 78% compared to the control. This indicates that organic compost can promote plantlet development by improving water retention and nutrient availability, reducing density, and increasing porosity of substrate, possibly by optimizing the physicochemical properties of the substrate. Excessive concentrations of organic compounds may have negative effects, such as increased density and decreased macroporosity, favoring water retention in excess, and increasing some nutrients at a toxic level. The findings of this work are relevant for optimizing the rooting process of this species. From proteomic analysis, we observed that organic compost treatment modulated the abundance of certain proteins. For instance, actin and calreticulin proteins showed a higher accumulation in plantlets treated with 25% organic compost compared to control, and acetohydroxy-acid reductoisomerase protein was unique in plantlets  in the 25% organic compost treatment. These results suggests a specific role of these proteins on better shoot rooting with organic compounds. Ribulose bisphosphate carboxylase/oxygenase activase, chloroplastic protein was showed higher accumulation in plantlets in the control treatment, while heat shock cognate 70 kDa protein (Hsc70) was unique in plantlet at control, suggesting the role of this proteins on reduced root induction. These findings showed that organic compounds can be applied to improve root induction in A. lebbeck

Agradecimentos: UENF; Graduate Program in Plant Biotechnology; Faperj; Capes; CNPq