Silicon and phytohormone-based biostimulant applied to eucalyptus seedlings under water stress conditions

The expansion of eucalyptus cultivation to new areas with unfavourable environmental conditions can bring the risk of severe water stress at the beginning of seedling growth, which requires management or the use of agents that mitigate this condition. Therefore, the aim of this study was to evaluate the effects of silicon and biostimulant application on eucalyptus seedlings under water stress conditions. The experiment was installed in a randomized block design in a 5 x 2 factorial scheme, where five doses of silicon dioxide (SiO2 - 91%) incorporated into the substrate (0.0; 1.17; 2.33; 3.50 and 4.66 g L-1) were tested in the presence (20.0 mL L-1 water) or absence of Stimulate® biostimulant, with five replicates. The experiment was installed in 6.0 L-1 polyethylene bags under simulation of water stress in an open area. The combined application of silicon and biostimulant influenced stem diameter and root dry mass. The dry mass of the leaves and the total height of the seedlings were only influenced by the application of silicon. The SiO2 doses, which in combination with the biostimulant or not, provided higher values for the total height, stem diameter, dry mass of leave, stem and root parameters, ranged from 2.90 to 3.83 g SiO2 L-1. Both the occurrence and severity of water stress symptoms were modified by the application of silicon, combined or not combined with biostimulants. The isolated application of biostimulant and silicon at a dose of 4.66 g L-1 as well as the use of this dose in combination with biostimulant resulted in longer and less severe stress symptoms.