Calidad de plantines de Eucalyptus smithii en función del tamaño de tubetes y del uso de reguladores de crecimiento

Eucalyptus smithii has become a relevant species within the Uruguayan forestry sector, mainly as an alternative to Eucalyptus globulus, whose productivity declined following the emergence of Teratosphaeria nubilosa in 2007. In addition to its adequate silvicultural performance, it shows suitability for timber and pulp production, as well as frost tolerance. However, episodes of mortality during the early stages of the crop have been reported in recent years, without a precise diagnosis of their causes. In this context, this study evaluated strategies to improve the quality of seedlings intended for field establishment by analyzing the effect of growth regulators on root development and the influence of container type during the nursery stage. The experiment was conducted at the Saucedo nursery (Solís de Mataojo, Lavalleja, Uruguay) under a completely randomized factorial design, considering two factors: container type (three levels) and hormonal application (with and without application), with three replicates per treatment. The hormonal treatment was applied foliarly 99 days after sowing, using a solution of naphthaleneacetic acid (NAA) and aminoethoxyvinylglycine (AVG) at concentrations of 600 mg L⁻¹ and 125 mg L⁻¹, respectively. Three container types differing in design and volume were evaluated: large container (325.125 cm³), small container (30.49 cm³), and square container (172.40 cm³). Two morphological evaluations were performed: at the time of application on a subsample of seedlings from each treatment, and at 173 days after sowing, including a total of 342 seedlings. In both evaluations, root collar diameter (RCD), height (H), leaf dry weight (LDW), stem dry weight (SDW), and root dry weight (RDW) were measured, and total dry weight (TDW) and quality indices were calculated. Results showed that container size was the main factor determining seedling growth and quality, whereas the hormonal treatment mainly influenced biomass allocation among seedling organs and morphological balance. In general, larger containers promoted greater growth and biomass accumulation, while hormonal application favored a higher proportion of root development and improved quality indicators. The joint analysis of morphological variables and quality indices demonstrated that larger plant size does not necessarily imply better quality, highlighting the importance of an integrated evaluation in forest seedling production.